Standard Neoadjuvant Chemotherapy Research Articles

Neoadjuvant Chemotherapy with Concurrent Letrozole for Estrogen Receptor-Positive and HER2-Negative Breast Cancer: An Open-Label, Single-Center, Nonrandomized Phase II Study (NeoCHAI).

The role of combining neoadjuvant endocrine therapy with conventional chemotherapy remains unclear; therefore, we conducted an open-label, single-center, nonrandomized phase II trial to assess the effect of this combination. Patients with previously untreated stage II or III HR-positive, HER2-negative breast cancer received concurrent letrozole 2.5 mg with standard neoadjuvant chemotherapy. The primary endpoint was pathologic complete response (pCR) at the time of surgery. We used Simon's minimax two-stage design; a pCR rate > 6% was necessary at the first stage to continue. Between November 2017 and November 2020, 53 women were enrolled in the first stage of the trial. Their median age was 49 years (range, 33-63), and 60% of them were premenopausal. Subsequently, 66% and 34% of patients with clinical stages II and III, respectively, were included; 93% had clinically node-positive disease. Two patients (4%) achieved pCR after neoadjuvant chemo-endocrine treatment, which did not satisfy the criteria for continuing to the second stage. The overall response rate was 83%. During the median follow-up of 53.7 months, the 3-year disease-free survival and overall survival rates were 87% and 98%, respectively. Neutropenia was the most common grade 3/4 adverse event (40%), but rarely led to febrile neutropenic episodes (4%). Myalgia (32%), nausea (19%), constipation (17%), heartburn (11%), oral mucositis (9%), and sensory neuropathy (9%) were frequently observed, but classified as grade 1 or 2. No deaths occurred during preoperative treatment. The addition of letrozole to standard neoadjuvant chemotherapy was safe and beneficial in terms of overall response rate, but did not provide a higher pCR rate in locally advanced HR-positive, HER2-negative breast cancer. Further research is needed to enhance neoadjuvant treatment strategies for this cancer subtype.

Phase III randomized trial comparing neoadjuvant paclitaxel+platinum to 5-fluorouracil+platinum in esophageal/GEJ squamous cell carcinoma.

Standard neoadjuvant chemotherapy (NACT) for locally advanced esophageal/gastroesophageal junction squamous cancer (LAEGSC), 5-fluorouracil (5FU)+platinum, is toxic and logistically challenging; alternative regimens are needed. Phase III randomized open-label non-inferiority trial at Tata Memorial Center, India, in resectable LAEGSC. Patients were randomized 1:1 to three cycles of 3-weekly platinum (cisplatin 75 mg/m2 or carboplatin AUC 6) with paclitaxel 175 mg/m2 (day 1) or 5FU 1000 mg/m2 continuous infusion (days 1-4), followed by surgery. Between August 2014 and June 2022, we enrolled 420 patients; 210 to each arm. Significantly more patients on paclitaxel + platinum (194 (92.3%)] received all 3 chemotherapy cycles than on 5FU+platinum (170 [85.9%]), P = .009. 5FU + platinum caused more grade ≥ 3 toxicities (124 [69.7%]) than paclitaxel + platinum (97 [51.9%]), P = .001. Surgery was performed in 131 (62.4%) patients on 5FU + platinum vs 139 (66.2%) on paclitaxel + platinum, P = .415. Paclitaxel + platinum resulted in higher pathologic primary tumor clearance (33 [25.8%]) vs 17 [15%]; P = .04), and pathologic complete responses in 21.9% compared to 12.4% from 5FU + platinum, P = .053. Median OS was 27.5 months (95% CI, 18.6-43.5) from paclitaxel + platinum, which was non-inferior to 27.1 months (95% CI, 18.8-40.7) from 5FU + platinum; HR, 0.89 (95% CI, 0.72-1.09); P = .346. Neoadjuvant paclitaxel + platinum chemotherapy is safer, and results in similar R0 resections, higher pathologic tumor clearance and non-inferior survival, compared to 5FU + platinum. Paclitaxel + platinum should replace 5FU + platinum as NACT for resectable LAEGSC. CTRI/2014/04/004516.

367. IMPACT OF NEOADJUVANT IMMUNOTHERAPY ON POSTOPERATIVE COMPLICATIONS IN RESECTABLE ESOPHAGEAL ADENOCARCINOMA

Abstract Background Several studies are ongoing on the use of immunotherapy in the neoadjuvant setting for esophageal and gastroesophageal junction cancer but it is unclear the effect of an increased activation of the immune system on surgery and the postoperative course. Methods This multicenter retrospective cohort study included data from 3 high-volume centers for upper-GI surgery. Only patients with esophageal adenocarcinoma who underwent neoadjuvant therapy and radical surgery between 2015 and 2022 were included. Clinical characteristics and the postoperative outcomes were compared between patients who received standard neoadjuvant therapy or chemotherapy plus immunotherapy. A 1-to-1 matched comparison was also performed. The difference in overall survival (OS) and disease free survival (DFS) between the two groups was also evaluated. Results Overall, 563 patients were included and 21 received preoperative Pembrolizumab or Trastuzumab combined with at least a couple of chemotherapy drugs. The incidence of complications was 47% in the group with immunotherapy and 40.7% in the other group (p=0.53). The matched analysis confirmed no differences in rate of complications (p>0.99), gravity of complications (p=0.17) and pulmonary complications (p>0.99). Anastomotic leak rate was 4.7% in the immunotherapy group and 19% in the other one (p=0.34). Overall survival and disease free survival were comparable (respectively p=0.4 and p=0.9) also after the matched analysis (respectively p=0.15 and p=0.52). Conclusion Neoadjuvant immunotherapy-based regimen does not affect the postoperative course, in particular it does not appear to aggravate the major complications of esophagectomy.

Prognostic impact of shift to low visceral fat mass after neoadjuvant chemotherapy in patients with esophageal cancer.

Based on the JCOG1109 trial, it is suggested that the combination of docetaxel, cisplatin, and 5-fluorouracil (DCF) could potentially become a standard neoadjuvant chemotherapy regimen, alongside the conventional 5-fluorouracil and cisplatin (CF) therapy, for esophageal cancer. However, there are few reports on the impact of body composition changes associated with neoadjuvant chemotherapy on prognosis. Our study aimed to explore the effect of different neoadjuvant chemotherapy regimens on body composition during treatment and the impacts of body composition changes on their prognosis. This is a retrospective study of 215 patients with advanced thoracic esophageal cancer who had surgery after neoadjuvant chemotherapy from 2013 to 2019. Computed tomography scans were performed before and after neoadjuvant chemotherapy to assess body composition. Skeletal muscle mass index (SMI) was calculated by dividing total skeletal muscle mass at the 3rd lumbar level by the square of height, while visceral and subcutaneous fat masses were measured at the level of umbilicus. Patients in the lowest 25% of both sexes were classified into the low visceral fat and low subcutaneous fat groups, respectively. Of the patients enrolled, 178 were male and 37 were female. Among them, 91 had clinical Stage II disease, and 124 had clinical Stage III disease. Additionally, 146 patients received neoadjuvant chemotherapy CF, and 69 received neoadjuvant chemotherapy DCF. Comparing the DCF and CF groups, the DCF group consisted of significantly younger patients (p < .01), a higher proportion of males (p = .03), and a greater number of clinical Stage III cases (p < .01). However, although percent change in SMI and visceral fat mass was not significantly different between two regimens, percent change in subcutaneous fat mass was significant in the DCF group. The major prognostic factors for patients undergoing surgery after neoadjuvant chemotherapy for thoracic esophageal cancer were clinical Stage III, transition to low visceral fat, and response rating (SD/PD), while the specific neoadjuvant chemotherapy regimen did not significantly influence the outcomes. This study suggests that prevention of the shift to low visceral fat throughout the neoadjuvant chemotherapy process should improve patient outcomes.

Real-world data on adjuvant capecitabine after standard neoadjuvant chemotherapy for triple negative breast cancer.

Neoadjuvant chemotherapy (NACT) has become the standard of care for patients with triple-negative breast cancer (TNBC) with tumors > 1 cm or positive axillary nodes. Pathologic complete response (pCR) has been used as an endpoint to select patients for treatment scaling. This study aimed to examine the benefit of adding adjuvant capecitabine for TNBC patients who did not achieve pCR after standard NACT in a real-world scenario. This retrospective cohort study included all patients with TNBC who underwent NACT between 2010 and 2020. Clinicopathological data were obtained from the patient records. Univariate and multivariate analyses were conducted at the 5 years follow-up period. We included 153 patients, more than half of whom had stage III (58.2%) and high-grade tumors (60.8%). The overall pCR rate was 34.6%, and 41% of the patients with residual disease received adjuvant capecitabine. Disease-specific survival (DSS) among the patients who achieved pCR was significantly higher (p<0.0001). Residual disease after NACT was associated with detrimental effects on DSS. In this cohort, we did not observe any survival benefit of adding adjuvant capecitabine for patients with TNBC subjected to NACT who did not achieve pCR (p=0.52). Our study failed to demonstrate a survival benefit of extended capecitabine therapy in patients with TNBC with residual disease after NACT. More studies are warranted to better understand the indication of systemic treatment escalation in this scenario.

Neoadjuvant anlotinib combined with penpulimab for resectable locally advanced esophageal squamous cell carcinoma (ESCC): Updated data from a prospective, phase II trial.

e16079 Background: Neoadjuvant chemoradiation therapy followed by radical surgery has been extensively recommended for locally advanced esophageal squamous cell carcinoma (ESCC). However, toxicities and challenges to the subsequent surgery limit its wide clinical application. Immune checkpoint inhibitors combined with antiangiogenesis have synergistic effects and have shown good therapeutic effects in previous studies, as well as fewer side effects. Here, we tested a novel combination of anlotinib (an antiangiogeneic kinase inhibitor) and penpulimab (an anti-PD-1 antibody), devoid of radio- or chemo-therapy, for the neoadjuvant therapy of locally advanced ESCC. Methods: In this prospective, single-arm, phase II clinical trial (ChiCTR2200064848), patients(pts) with resectable locally advanced ESCC (clinical stage III-IVa) were recruited. The study was designed using a two-stage minimax approach. The planned sample size was 40 pts would provide 80% power at a one-sided alpha error of 5%, threshold pathological complete response (pCR) of 16% and expected pCR of 30%. Pts received neoadjuvant therapy with anlotinib (8 mg, po, D1-14, Q3W) combined with penpulimab (200 mg, ivgtt, Q3W) for 2 cycles. Six to eight weeks later, pts underwent radical surgery after exclusion of contraindications. The primary endpoint was pCR rate. Secondary endpoints included tumor regression grade (TRG), R0 resection rate, objective response rate (ORR) and safety profile. Results: From Jan 2023 to Nov 2023, 25 pts (19 males and 6 females) were enrolled with a median age of 67 years (range: 50-74). A concerning 92% were diagnosed with lymph node metastasis. Moreover, 85% (22/25) pts exhibited medical contraindications, including pure red cell aplasia, compromised pulmonary function, and poor nutritional status, etc.) rendering them ineligible for standard neoadjuvant chemoradiotherapy or chemotherapy. All pts were available for efficacy assessment, ORR and DCR were 48.0% and 96.0%, respectively. Of these, 21 pts underwent esophagectomy, with an R0 resection rate of 90.5% (19/21). The study's initial phase successfully achieved its primary endpoint, with a pCR rate of 19.0% (4/21). Furthermore, the major pathological response (MPR) was 28.6% (6/21). The most common TRAEs (≥10%) included hypertension (28.0%), hand-foot syndrome (20%), fatigue (20%), abdominal pain (12%), toothache (12%). Grade 3-4 TRAEs were observed in 12.0% of the patients (3/25), and no reports of grade 5 TRAEs. Conclusions: Preliminary results from the initial stage suggest that anlotinib combined with penpulimab as a neoadjuvant treatment for ESCC showed promising safety and efficacy, especially for those deemed unsuitable for neoadjuvant chemoradiation or chemotherapy. More ESCC pts would be recruited in the future. Clinical trial information: ChiCTR2200064848.

Incidence and time to onset of immunotherapy-related adrenal insufficiency in the I-SPY2 trial.

584 Background: I-SPY2 was the first randomized trial to demonstrate an improvement in pCR and EFS when Immune Checkpoint Inhibitors (ICI) were added to standard neoadjuvant chemotherapy. This finding was validated in the phase 3 KEYNOTE 522 trial for triple-negative breast cancer, leading to approval of pembrolizumab (pembro) in this setting. ICIs add the risk of immune-related adverse events (irAEs); while most irAEs are reversible, endocrinopathies appear to persist. Higher rates of adrenal insufficiency (AI), either from primary adrenalitis or hypophysitis, have been reported with ICI-based therapy (tx) in early breast cancer (EBC) compared to advanced disease. Here we describe the incidence and time of onset of AI with ICI-based tx in I-SPY2. Methods: I-SPY2 is a multicenter, phase 2 trial using response-adaptive randomization within biomarker subtypes defined by hormone receptor, HER2, and MammaPrint status to evaluate novel agents in the neoadjuvant setting in patients (pts) with high-risk EBC. Treatment included weekly paclitaxel (T) plus ICI-based tx x 4 cycles, followed by doxorubicin/cyclophosphamide (AC) every 2-3 weeks x 4. 6 completed investigational arms included ICIs: T+pembro x 4, T+pembro x 8 (+/- AC), T+pembro+SD101 (TLR9 agonist), T+durvalumab+olaparib, T+cemiplimab (cemi), and T+cemi+REGN3767 (anti-LAG-3). AI diagnoses were made by treating providers with review from two board certified endocrinologists. AI was defined as AM serum cortisol level &lt; 3 mcg/dl in absence of recent glucocorticoid treatment. If ACTH was low or normal, pt was dx with hypophysitis; if ACTH was elevated, pt was dx with primary AI. Results: 442 pts in I-SPY2 received ICI-based tx; 11.8% (n=52) developed AI (primary+hypophysitis). Mean age of pts who developed AI was 47.3 vs 48.6 yrs in those who did not (p=0.44). Incidence of AI was highest in arms with dual immune modulation (18.1%) as compared to single ICI tx (8.5%). Median time to onset varied by arm, ranging from 92-204 days from first ICI dose. While some cases occurred during ICI tx (13.5%), the majority occurred between 12-24 wks after tx initiation, with 21.2% diagnosed after completion of all tx. The majority (94.2%) of pts with AI were symptomatic; the most common presenting symptoms included fatigue (59.6%), nausea (48.1%), and vomiting (34.6%). All pts with AI remain on glucocorticoid replacement tx. Conclusions: The incidence of AI in EBC is higher than has previously been reported in advanced disease, with higher rates observed in those tx with dual immune modulation. No correlation was observed with age; correlation of AI with response predictive subtype and other clinicopathologic features is ongoing and will be presented. Given the high incidence of AI in EBC, close monitoring in the peri/postoperative setting and education of pts and providers is critical, as risk persists even after completion of tx. Work to identify risk factors for AI is ongoing. Clinical trial information: NCT01042379 .

Prognosis and influencing factors of ER-positive, HER2-low breast cancer patients with residual disease after neoadjuvant chemotherapy: a retrospective study

Previously, we found that patients with estrogen receptor (ER)-positive, HER2-low breast cancer are resistant to neoadjuvant chemotherapy (NACT) and have worse outcomes than those who achieve pathological complete response (pCR) after NACT. This study aimed to investigate the prognosis and influencing factors in these patients. A total of 618 patients with ER-positive breast cancer who received standard thrice-weekly NACT were enrolled, including 411 patients with ER-positive, HER2-low breast cancer. Data on the clinicopathological features of these patients before and after NACT were collected. Univariate and multivariate Cox regression analyses were used to identify the independent factors affecting 5-year disease-free survival (DFS). Among the ER-positive, HER2-low patients, 49 (11.9%) achieved a pCR after NACT. A significant difference in survival was observed between patients with and without residual disease after NACT. Additionally, changes in immunohistochemical markers and tumor stages before and after NACT were found to be significant. According to univariate and multivariate analyses, cN_stage (P = 0.002), ER (P = 0.002) and Ki67 (P = 0.023) expression before NACT were significantly associated with 5-year DFS, while pT_stage (P = 0.015), pN_stage (P = 0.029), ER (P = 0.020) and Ki67 (P < 0.001) levels after NACT were related to 5-year DFS in ER-positive, HER2-low patients with residual disease. Our study suggested that high proliferation, low ER expression and advanced stage before and after NACT are associated with a poor prognosis, providing useful information for developing long-term treatment strategies for ER-positive, HER2-low breast cancer in patients with residual disease in the future.

Measuring cfDNA integrity as a biomarker for predicting neoadjuvant chemotherapy response in breast cancer patients: a pilot study.

Circulating cell-free DNA (cfDNA) is a promising biomarker for predicting treatment response and disease outcomes in Breast Cancer (BC) patients undergoing neoadjuvant chemotherapy (NAC). To determine if cfDNA originates from tumors, matching tumor and cfDNA gene mutations are necessary, often requiring tumor DNA sequencing. We assessed plasma cfDNA integrity by measuring concentrations and ratios of larger-to-smaller Alu DNA fractions as a potential biomarker, eliminating the need for prior tumor sequencing. We included patients with localized and/or locally advanced BC receiving standard NAC alone or in combination with immunotherapy and/or anti-HER2 targeted therapy. Blood samples were collected before treatment, every 2 weeks during treatment, and before surgery. Of the 38 evaluated patients, only 28 completed the protocol and underwent surgery after NAC. Seven patients (25%) achieved a pathologic complete response (pCR). We found that cfDNA integrity (cfDNAI) levels at 15days after starting NAC were significantly higher in patients who achieved pCR (p = 0.045) and correlated significantly with Disease-Free Survival (DFS) in univariate analysis (p = 0.0371). Evaluation of cfDNAI 2 weeks after NAC initiation appears to be an early biomarker for tumor pCR and DFS. Measuring Alu fragments of different lengths may replace techniques requiring prior tumor sequencing to measure ctDNA, reducing costs and complexity of cfDNA serial measurements in BC patients undergoing NAC.

Mitomycin C in the treatment of early triple-negative locally advanced BRCA-associated breast cancer

Rationale. BRCA1 associated triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer. At the same time, carcinomas that develop in carriers of BRCA1 mutations are characterized by extremely high sensitivity to DNA-damaging chemotherapy. Mitomycin C alone or in combination with platinum agents has already demonstrated promising results in the treatment of BRCA-associated ovarian cancer (OC) and metastatic breast cancer. In this article, we present the results of a retrospective study aimed at comparing standard neoadjuvant chemotherapy regimens (NACT) with mitomycin-based regimens for primary locally advanced BRCA1-associated TNBC.The aim of the study is to determine the effectiveness of the combination of mitomycin and platinum compounds during neoadjuvant therapy in patients with primary locally advanced BRCA1 – associated TNBC.Materials and methods. The study included 89 patients diagnosed with primary locally advanced BRCA1-associated TNBC. Patients were divided into three groups depending on the therapy: 1) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel (n = 48) (AC + T), 2) 4 cycles of anthracycline and cyclophosphamide followed by 12 weekly injections of paclitaxel and carboplatin (n = 27) (AC + TCbP), 3) mitomycin C plus platinum followed by 12 weekly injections of paclitaxel (n = 14) (MR + T). Pathological complete response (pCR) rates were compared.Results. The pCR rate in the MP+T group was 10/14 (71%). In patients with BRCA1-associated breast cancer who received AC + T and AC + TCbP regimens as NACT, the pCR rate was 17/48 (35%) and 19/27 (70%), respectively. The difference in pCR rate between mitomycin-containing therapy and the standard AC + T regimen was statistically significant (p = 0.03); the frequency of regressions was comparable to the frequency in the AC + TCbP group. During the 20-month follow-up period, no relapses were observed in the MR + T group. Relapses were more frequent in the AC + T group compared with the AC + TCbP group (16/48 (33%) vs 1/27 (4%), p = 0.003, Fisher’s exact test). The toxicity profile of the mitomycin-containing regimen included hematologic adverse events, the most common of which were anemia and leukopenia. Compared to standard regimens, nausea was significantly less pronounced. No patients reported alopecia with this regimen.Conclusions. The addition of mitomycin C to neoadjuvant therapy for BRCA1-associated TNBC may be a promising treatment option for this category of patients and merits further study.

Abstract PO4-03-07: The impact of chemotherapy relative dose intensity on pathological complete response in patients with triple negative breast cancer treated with neoadjuvant chemotherapy

Abstract Background: Neoadjuvant chemotherapy (NACT) is the preferred treatment approach for early-stage triple negative breast cancer (TNBC). Achieving pathologic complete response (pCR) after NACT is associated with improved event-free survival and overall survival in patients with TNBC. Major research efforts have been deployed to identify predictive biomarkers for pCR in TNBC. However, the values of chemotherapy (CT) relative dose intensity (RDI) in predicting pCR remain unclear. Methods: A retrospective analysis was conducted among 96 consecutive patients with early stage TNBC who received NACT between February 2018 and January 2023 at the University of Naples Federico II (Naples, Italy). Patients’ demographics, clinical-pathological features, and type of CT schedules were retrieved from electronic medical records. pCR was defined as the absence of residual invasive or in situ carcinoma in primary tumor and/or lymph nodes, upon chemotherapy administration. RDI was calculated as the ratio of delivered to planned CT dose intensity. RDI was defined as low if &amp;lt; 85% or high if ≥85%, respectively. Univariate and multivariate logistic regression were used to evaluate the association between age, tumor stage, RDI, CT regimen dose type, and pCR. Results: All patients were included in the analysis. Median age at diagnosis was 51 years (range 28-75). Sixty-five (68%) and 31 (32%) patients were diagnosed with stage II and stage III TNBC, respectively. Nineteen (19%) patients received a sequential schedule of anthracycline plus cyclophosphamide (AC) and a taxane (T). Sixty-one (64%) patients received AC followed by concurrent carboplatin-paclitaxel (CaP). Sixteen (17%) patients received the anti-PD1 pembrolizumab in addition to ACCaP chemotherapy backbone (ACCaP-Pem). Fifty-four (56%) patients received a dose-dense AC-based CT. A pCR was achieved in 59 (61%) patients. Interestingly, patients who received a dose-dense AC based neoadjuvant CT had higher chance to achieve a pCR compared with those treated with a non dose-dense AC based CT (70% vs 46%, p = 0.03). Overall, 79 (82%) and 17 (18%) patients received a RDI high and RDI low CT, respectively. No difference in terms of age, body mass index, performance status, tumor stage, type of chemotherapy was observed between the two groups (Table 1). At univariate analysis RDI high (OR 5.18, 95%CI: 1.65-16.31, p=0.005) and dose dense AC-based CT (OR 2.42, 95%CI: 0.18-0.97, p=0.04) were significantly associated with pCR. In a multivariate model including RDI, age, tumor stage, and AC regimen dose type, RDI was the only variable independently associated with pCR (OR 4.60, 95% CI: 1.40-15.06, p = 0.01). Conclusion: A chemotherapy RDI≥ 85% independently predicts pCR in early stage TNBC patients treated with standard NACT. In our cohort, one in five patients received a suboptimal chemotherapy dose intensity affecting at least in part tumor response. Studies with larger TNBC patient populations are warranted to confirm the impact of RDI on pCR and long-term outcomes. Table 1 Citation Format: Roberto Buonaiuto, Giuseppe Neola, Aldo Caltavituro, Paola Trasacco, Federica Pia Mangiacotti, Giovanna Pecoraro, Matteo Lambertini, Erica Pietroluongo, Pietro De Placido, Sabino De Placido, Valeria Forestieri, Mario Giuliano, Grazia Arpino, Carmine De Angelis. The impact of chemotherapy relative dose intensity on pathological complete response in patients with triple negative breast cancer treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-03-07.

Abstract PO5-17-09: Event-free survival in HER2-low vs HER2-zero breast cancer patients submitted to neoadjuvant chemotherapy

Abstract Background: Breast cancer (BC) with low expression of HER2 (HER2-low) might constitute a group of tumors with unique clinical and biological characteristics. However, the prognostic impact of HER2-low status vs HER2-zero in terms of pathological complete response (pCR) and event-free survival (EFS) after neoadjuvant chemotherapy (NACT) remains controversial. The aim of this study was to evaluate pCR and EFS rates in HER2-low vs HER2-zero early BC patients treated with NACT. Methods: In this cross-sectional study, we analyzed 565 consecutive patients with HER2-low and HER2-zero early BC submitted to neoadjuvant therapy from 2017 to 2021 in a single academic center. Patients with biopsy-confirmed stage I-III BC, with HER2-low or HER2-zero status, submitted to locoregional therapy after NACT were included. Clinical and pathological characteristics, pathological response, treatment protocol and RFS were analyzed and considered for statistical analysis. HER2-low was defined by IHC 1+, or 2+ ISH non-amplified; HER2-zero was defined by IHC 0. Pathological response was determined locally, and pCR defined as the absence of residual invasive disease with or without ductal carcinoma in situ in the breast and axilla. EFS was defined as the time from diagnosis to distant recurrence, a second primary, or death from any cause, whichever occurred first. Results: 441 patients were included in the analysis, 236 (53.5%) patients with HER2-low tumors, and 205 (46.5%) with HER2-zero tumors. Overall, 279 (63.3%) were estrogen receptor (ER)-positive tumors, and 162 (36.5%) were ER-negative tumors. Among ER-positive tumors, 166 (59.5%) had HER2-low status, and 113 (40.5%) were HER2-zero. For the ER-negative subgroup, the corresponding rates were 70 (43.2%) and 92 (56.8%), respectively. Most patients had stage II-III BC (423/441; 96%), and 20.2% (89/441) had high nodal tumor burden. Many patients received anthracycline- and taxane-based NACT (425/441; 96.4%), and over 90% (148/162; 91.3%) of ER-negative patients received a platinum agent. The overall pCR rate were 18.1%. Among ER+ tumors, pCR rates were 6.4%, 6.0%, and 7.0% in the overall, HER2-low and HER2-zero tumors, respectively. In ER- tumors, the corresponding pCR rates were 38.3%, 35.7, and 40.2%, respectively. The differences in pCR rates between HER2-low and HER2-zero tumors were not statistically significant (ER-positive, p=0.724; ER-negative, p=0.559). After a median follow-up of 42 months, 90 EFS events occurred. In the HER2-low group there were 56 (23.7%) EFS events, and 34 (16.6%) EFS events in the HER2-zero (HR 1.19; 95% CI 0.77-1.82; p=0.427). Among 279 patients in the ER-positive group there were 48 events, 32 in the HER2-low subgroup and 16 in the HER2-zero group (HR 1.16; 95% CI 0.64-2.13; p=0.622). Among 162 ER-negative tumors there were 42 events, 24 in the HER2-low subgroup, and 24 in the HER2-zero subgroup (HR 1.56; 95% CI 0.84-2.88; p=0.158). NACT discontinuation occurred in 86 patients (ER-positive: 45, 16.1%; ER-negative: 41, 25.3%), mainly due to toxicity (anthracycline-taxane: 10.0%; platinum: 11.7%). Disease progression during NACT were reported in 6.8% (30/441) of patients. Conclusions: Our results show similar pCR rates and RFS among HER2-low and HER2-zero early BC patients after standard NACT, which are consistent with the current literature. Despite the predictive role of low HER2 expression in selecting patients for novel antibody-drug conjugates (ADCs) therapy, its prognostic value could not be confirmed. Citation Format: Guilherme Sartori, Susana Ramalho, Leonardo Roberto da Silva, Tomás Reinert, Mahira Lopes Da Rosa, Grazielle Morais Tavares, Vivian Vasconcelos, Higor Mantovani, Ana Elisa Ribeiro Da Silva Cabello, Guilherme Coelho, Jovana Mandelli, Facundo Zaffaroni, César Cabello, Carlos Barrios, Marcia Silveira Graudenz. Event-free survival in HER2-low vs HER2-zero breast cancer patients submitted to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-17-09.

Abstract PO5-26-01: Assessing the effect of multimodal therapy in massive fungating breast cancers without distant metastasis

Abstract Background: Massive fungating breast cancers (MFBCs), which comprise exudative, foul-smelling tumors, the size of a child’s head or involve extensive ulceration are classified as locally advanced breast cancers. The National Comprehensive Cancer Network guidelines recommend preoperative neoadjuvant chemotherapy in patients with locally advanced breast cancer without distant metastases. However, limited evidence is available regarding the successful treatment of fungating breast cancers. In clinical practice, many fungating breast cancer cases are treated as stage IV tumors. This study aimed to investigate whether multimodal therapy, including surgery for giant breast cancers, can improve survival rates and whether the survival rates are comparable to those of other stage III breast cancers. Subjects and methods: Out of 1480 cases of primary breast cancer diagnosed at our hospital between June 2012 and March 2020, 123 patients with clinical stages IIIA–IIIC were chosen for analysis. Furthermore, 29 of these patients with MFBC were selected. During multimodal therapy for selected patients with fungating breast cancer, difficulties were encountered in some patients with single-stage skin suturing and closure after standard neoadjuvant chemotherapy. These patients underwent surgery with an additional skin flap or skin grafting. Furthermore, radiation therapy was added as needed. We compared the survival rates of these patients with those of patients who received drug therapy only according to the therapeutic protocol for Stage IV. Survival rates of patients with MFBC and other stage III breast cancers were also compared. Statistical analyses were conducted using the Kaplan–Meier curve and the log-rank test. Results: Of the 29 patients with MFBC, 22 (75.9%) and seven (24.1%) were treated with multimodal and palliative therapies, respectively. The median age and follow-up period of the multimodal therapy group were 62 (range: 43–94) years and 67 (range, 32–131) months, respectively. The corresponding values for the palliative therapy group were 79 (range: 42–88) years and 31 (range: 2–96) months. All patients in the palliative treatment group were hormone receptor positive and HER2 negative, and treatment with hormone therapy was initiated. The 7-year survival rate was significantly higher in the multimodal therapy group than in the palliative treatment group (92.3% vs. 68.6%, p = 0.0317). Furthermore, the 5-year distant recurrence-free rate was higher in the multimodal treatment group (79.3% vs. 63.5%). Local recurrence did not occur in any patient in the multimodal treatment group. There was no significant difference in the 7-year survival rates between patients with MFBC and those with other stage III breast cancers (86.8% vs. 75.3%; p = 0.239). Triple-negative breast cancer accounted for 20.8% (20 96) of the other stage III breast cancers, but none of these were MFBCs. Conclusions: Clinically, MFBCs are often palliatively treated as stage IV tumors, even in the absence of distant metastasis. However, the survival rate was significantly higher in the multimodal therapy group than in the palliative treatment group. Furthermore, the survival and distant recurrence-free rates for MFBC were higher than those for other stage III breast cancers. Therefore, patients with MFBCs should be actively treated using curative treatments. Citation Format: Tamaki Tamanuki, Maki Namura, Tomoyoshi Aoyagi, Haruhito Sakata, Mika Iwai, Shinichirou Shimizu, Hiroshi Matsuzaki. Assessing the effect of multimodal therapy in massive fungating breast cancers without distant metastasis [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-26-01.

Abstract PO1-18-04: Neoadjuvant pembrolizumab + decitabine followed by standard neoadjuvant chemotherapy for locally advanced HER2- breast cancer (NCT02957968)

Abstract Background: Higher levels of stromal tumor-infiltrating lymphocytes (sTILs) in breast cancers are associated with increased likelihood of pathologic complete response (pCR) to chemotherapy and improved outcomes. DNA methyltransferase inhibitors (DNMTi) can augment immune responses to cancers by upregulating tumor antigen and MHC expression, decreasing numbers and activity of myeloid derived suppressor cells (MDSC), and increasing responsiveness of T lymphocytes. We have shown that the DNMTi decitabine augments the effectiveness of immunotherapy against murine triple negative breast cancer (TNBC) using murine 4T1 and E0771 mammary carcinoma models. Methods: In a single-arm phase 2 study, patients with HER2-negative breast cancer who were candidates for neoadjuvant chemotherapy (NCT) received decitabine (15 mg/m2 × 4 doses over 5 days) followed by 2 doses of pembrolizumab (pembro) (200 mg, 2 weeks apart) – collectively, window immunotherapy – prior to starting NCT. Two research biopsies were obtained: 1 prior to the window immunotherapy and 1 afterwards, prior to starting NCT. Biopsies were analyzed using established procedures to quantify sTILs and PD-L1 expression. Patients proceeded to NCT and tumor resection per standard of care and were followed up for immune-related adverse events (irAEs) and response. The primary endpoint was change in sTILs. Key secondary endpoints were occurrence of irAEs and pCR following neoadjuvant treatment. After the study was opened, reported results of a phase 3 trial (KEYNOTE 522) led to allowing patients with TNBC to receive additional pembro (200 mg q3w) concurrently with standard NCT and adjuvantly following resection (Cohort A2). Results: 46 patients (median age 54.5 yrs, range 28-72; 71.7% White, 28.3% Black; 100% female) were enrolled and treated on study. 21 patients had TNBC and did not receive neoadjuvant pembro concurrently with NCT nor adjuvant pembro (Cohort A), 7 patients had TNBC and did receive neoadjuvant and/or adjuvant pembro (Cohort A2), and 18 patients were ER+ or PR+ and received neither concurrent nor adjuvant pembro (Cohort B). Blood samples collected after decitabine administration before the first pembro dose showed a 59% decrease (P&amp;lt; 0.01) in monocytic MDSCs compared to baseline; decrease in granulocytic MDSCs was not statistically significant. 37 patients had paired biopsies adequate for sTIL evaluation with a mean change from 23.4% to 30.3% (absolute change 6.9%, P&amp;lt; 0.001). Cohorts A/A2 experienced an absolute sTIL increase of 7.4% (P&amp;lt; 0.01); Cohort B experienced absolute sTIL increase of 6.1% (P=0.01). PD-L1 expression in tumors (H-score using MoAb 22C3 clone) increased by 43% (P&amp;lt; 0.01) across all cohorts. 16 of the 39 patients (41.0%) who proceeded to resection achieved pCR (n=12 of 27 [44.4%] in Cohorts A/A2 and n=4 of 13 [30.8%] in Cohort B). The most frequently reported irAEs were adrenal insufficiency (n=5, 10.9%), maculopapular rash (n=3, 6.5%), and hypothyroidism (n=3, 6.5%). Conclusions: Treatment in the pre-neoadjuvant window with decitabine and pembro could potentially sensitize breast cancers to standard NCT by recruitment of TILs to the tumor tissue. The treatment was well -tolerated at the tested doses. Funding: financial support and drug (pembrolizumab) were provided by Merck Citation Format: Harry Bear, Xiaoyan Deng, Dipankar Bandyopadhyay, Michael Idowu, Maciej Kmieciak, Monique Williams, Giovanni Archer, Lindsey Gwaltney, Patrick Dillon, Daniel Flora, Daniel Stover, Andrew Poklepovic, Mary Hackney, Masey Ross, Hetal Vachhani, Raphael Louie, Kandace McGuire, Amelia Grover, Tasnim Rahman, Amber Hendrix. Neoadjuvant pembrolizumab + decitabine followed by standard neoadjuvant chemotherapy for locally advanced HER2- breast cancer (NCT02957968) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-18-04.

Abstract PO2-25-03: Deciphering the immune molecular signature associated with pembrolizumab efficacy in the neoadjuvant setting of Triple-Negative Breast Cancer patients: a single-centre experience

Abstract Triple-negative breast cancer (TNBC) accounts for 15-20% of all breast cancers and is characterized by a high rate of recurrence, despite the improvement of the therapeutic approaches in recent years. Neoadjuvant chemotherapy (NACT) is the standard treatment for early-stage TNBC. Achieving a pathological complete response (pCR) is considered an essential prognostic factor for long-term outcomes. However, the percentage of pCR patients after NACT is limited to 30-40%, thus requiring the implementation of novel therapeutic strategies. Recently, by applying a morphology-guided spatial transcriptomic approach on Tru-Cut biopsies, we showed that intratumoral infiltrating lymphocytes (iTILs) and stromal Natural Killer (NK) cells are major determinants of chemotherapy efficacy in TNBC. These data highlight a complex three-dimensional organization of the tumor landscape and underline how spatiality and molecular activation of immune cells are essential to enhance the efficacy of neoadjuvant NACT in TNBC. The fact that immune cells are important players in this setting is corroborated by the clinical success shown by the KEYNOTE-522 study. This trial paved the way for the use of immunotherapy in neoadjuvant settings, obtaining a significant improvement in the patient’s overall response compared to standard NACT. Still, the implementation of chemotherapy with immunotherapy in the TNBC neoadjuvant treatment implicates several compelling questions, including how to further increase the percentage of patients with a complete response, overcoming resistance mechanisms, and how to improve the personalization of treatment, evaluating which patients can benefit from a therapy de-scalation or another combined therapeutic strategy. In this prospective cohort study, we decided to define the relevance of different immune populations in affecting pembrolizumab efficacy in the neoadjuvant treatment of TNBC patients. We treated 40 patients with an early-TNBC diagnosis with the KEYNOTE-522 regimen that consists of four cycles of an intravenous infusion of pembrolizumab plus paclitaxel and carboplatin, followed by four cycles of pembrolizumab plus epirubicin and cyclophosphamide. Only patients with evident side effects to immunotherapy administration were a priori excluded. Currently, 18 patients ended the neoadjuvant schedule and underwent surgical excision. Our data indicate that 15 patients displayed a pCR at the end of the therapy, whereas 3 patients displayed only partial response. To further clarify the immune dynamics that lead to a complete response to pembrolizumab in these patients, we collected peripheral blood before and after neoadjuvant treatment to isolate peripheral blood mononucleated cells (PBMCs). We applied a single-cell transcriptome analysis to shape any variations in circulating immune cells occurring during neoadjuvant treatment and associated with patient response. In addition, we collected residual tumors at surgery from partial responders and derived three-dimensional organoids that recapitulate the characteristics of the original patient tumor. These ex vivo organoid-based platforms are applied to clarify the molecular mechanisms driving neoadjuvant resistance. To this aim, we are performing co-cultures with autologous immune cells to identify novel combined therapeutic strategies to rescue pembrolizumab efficacy in these models. Overall, our study is defining the immune-related molecular mechanisms driving pembrolizumab and chemotherapy response in the neoadjuvant treatment of TNBC patients. Our findings can improve our understanding of which immune populations are determinant players in anti-TNBC immune response and can be proposed as novel biomarkers of pembrolizumab efficacy during the neoadjuvant treatment. Citation Format: Elisa Gasparini, Gloria Manzotti, Moira Ragazzi, Benedetta Donati, Federica Torricelli, Elisa Salviato, Alessandra Bisagni, Eleonora Zanetti, Alessandra Bologna, Saverio Coiro, Rita Vacondio, Guglielmo Ferrari, Giancarlo Bisagni, Carmine Pinto, Alessia Ciarrocchi, Francesca Reggiani. Deciphering the immune molecular signature associated with pembrolizumab efficacy in the neoadjuvant setting of Triple-Negative Breast Cancer patients: a single-centre experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-25-03.

Abstract PO4-03-13: High B7-H3 expression with low PD-L1 expression identifies armored-cold tumors suggesting potential anti-B7-H3 therapy in triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is generally regarded as the most aggressive subtype among breast cancer. B7 homolog 3 protein (B7-H3), also known as CD276, is an emerging immune checkpoint molecule, which plays a dual role in the immune system. Multiple anti-B7-H3 therapies has been raised, such as DS-7300, MGA271, MGD009, and B7-H3 chimeric antigen receptor T-cell immunotherapy (CAR-T). However, the expression of B7-H3 in TNBC and its value as a biomarker identifying therapeutic options has not been elucidated Methods: A total of 165 samples (83 non-TNBC and 82 TNBC) were included in this study, and 6 samples included paired para-tumor samples. In addition, 30 TNBC patients receiving standardized neoadjuvant chemotherapy (NAT) were recruited. After 8 cycles of NAT, the response to NAT was assessed by RECIST1.1 criterion before surgical operation. Moreover, multiple public cohorts of breast cancer and TNBC were obtained, including the TCGA dataset, the METABRIC dataset, the GSE176307 (durvalumab-based therapy) dataset, the PRJNA558949 (durvalumab-based therapy) dataset, the GSE194040 (paclitaxel-based therapy) dataset, and the GSE34138 (anthracycline-based therapy) dataset. Based on multiple in-house and public cohorts, we investigated the expression features of B7-H3 in breast cancer and checked the anti-tumor effect of the B7-H3 monoclonal antibody in mouse model. We also developed a novel classifier combined B7-H3 and PD-L1 expression in TNBC. Results: B7-H3 was highly expressed in tumor tissues in the in-house and the TCGA cohorts. B7-H3 expression did not differ significantly between non-TNBC and TNBC samples in the in-house and the TCGA cohorts, excepting for the METABIRC cohort. There was no notable difference in CD8+ cells infiltration between B7-H3 low and high expressed non-TNBC samples, but CD8+ cells was notably higher in the B7-H3 low expressed TNBC samples. The similar findings were also observed in the TCGA and the METABIRC cohorts. In addition, enrichment analysis of transcriptome data and analysis of in-house samples showed that B7-H3 was positively related to most collagens. Moreover, anti-B7-H3 therapy significantly inhibited tumor growth in mouse TNBC model, notably increased immune cells infiltration, and also reduced collagen deposition within the tumor. Given the notable value of PD-L1 in predicting immunotherapy responses, we also combined B7-H3 and PD-L1 expression to establish a novel subtyping strategy. TNBC patients with B7-H3highPDL1low feature exhibited the lowest anti-tumor immune infiltration and higher collagen deposition level. In the durvalumab-dependent cohort, paclitaxel-dependent cohort, anthracycline-dependent cohort, and our recruited NAT cohort, the B7-H3highPDL1low subgroup exhibited the lowest therapeutic response. Conclusions: Overall, this research provides a novel subtyping strategy based on the combination of B7-H3/PD-L1 expression that could potentially be applied to predict the therapeutic responses in TNBC, and suggests a potential biomarker-guided anti-B7-H3 therapy. Based on the classifier, we can select potential beneficiaries to deliver personalized medical services. Citation Format: Jie Mei, Yun Cai, Ziyi Fu, Yongmei Yin. High B7-H3 expression with low PD-L1 expression identifies armored-cold tumors suggesting potential anti-B7-H3 therapy in triple-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-03-13.

Abstract PO5-13-07: Prediction of recurrence in triple negative breast cancer patients after receiving neoadjuvanttreatment using plasma metabolomics

Abstract Background Early-stage triple-negative breast cancer (TNBC) is usually treated with neoadjuvant chemotherapy (NADC), but prognosis remains poor compared with other BC subtypes. Unfortunately, less than 30% of BC patients achieve pathological complete response (pCR) to NADC and the overall survival of TNBC when cancer spreads is estimated at 10-13 months. Complete response is associated with improved progression-free and overall survival rates, but more accurate prognostic markers are needed. In this study, we assessed the prognostic value of blood circulating metabolites by using targeted-based metabolomics. Methods Patients received standard neoadjuvant chemotherapy with epirubicin plus cyclophosphamide followed by paclitaxel. Blood samples were obtained upon completion of chemotherapy and before surgery. Pathological response to treatment was recorded according to the Miller &amp; Payne system, and categorized as partial (MP 1, 2, &amp; 3) or complete response (MP 4 &amp; 5). Blood samples were collected in EDTA tubes, centrifuged and plasma was stored at -80°C. After QC standard addition and methanol extraction of proteins, four fractions of the resulting extract were analysed: two by reverse-phase/UPLC-MS/MS methods with positive ion mode electrospray ionization (ESI), one by reverse phase/UPLC-MS/MS with negative ion mode ESI, and one by hydrophilic interaction liquid chromatography/UPLC-MS/MS) by Metabolon using a Thermo Scientific Q-Exactive mass spectrometer with a heated electrospray ionization source and an Orbitrap mass analyser. Using Metabolon's hardware and software, raw data were extracted, identified, QC processed and quantified using the area under the curve (AUC). Identified compounds were compared with library entries of purified standards or recurrent unknown entities. The prognostic capacity of each metabolite was assessed using BRB ArrayTools. Selected metabolites were validated using a targeted approach using compound standards as follows. Plasma samples were re-analysed by UPLC/MS using a Vanquish LC coupled to an Orbitrap Exploris 240 MS (Thermo Fisher Scientific) with positive and negative ionization mode ESI under polarity switching. Identification of compounds were performed by comparison of retention times (against in-house authentic standards), accurate mass (with an accepted deviation of 3ppm), and MS/MS spectra. These analyses were carried out by MS-Omics (Denmark). Results Twenty patients treated in the Medical Oncology Unit of the University Hospital of Jaén were recruited. Median age was 50 (31-76). Twelve patients obtained a pathological complete response. Median follow-up after surgery was 25 months. Seven patients eventually had distant metastases (2 in the lungs, 1 in the brain, 1 in the bones and 3 multi-site). Metabolon untargeted analysis identified and quantified 985 metabolites, 789 after xenobiotics exclusion. Survival analysis identified 16 metabolites related with distant relapse (p&amp;lt; 0.05). The ten metabolites with lower p-value were selected for targeted validation. Ms-Omics pipeline allowed absolute quantification of 5 metabolites, 3 of them showing high correlation (R &amp;gt;0.7) between both measurements (targeted and untargeted). Validation of the prognostic value of the candidate metabolites is ongoing in a larger TNBC cohort. Conclusions Metabolomics is a useful tool for the detection of simply assessable and cost-effective prognostic biomarkers in TNBC. Easily monitoring the presence of minimal residual disease is worth to be settled up in the clinical practice for the most aggressive molecular subtype of breast cancer. In this work we have defined a set of metabolites that could predict distant relapse events in TNBC patients treated with neoadjuvant chemotherapy. Further analyses are being carried out to validate the prognostic value of the proposed candidate metabolites. Citation Format: Pedro Sánchez-Rovira, Rocio Urbano-Cubero, Angelo Gamez Pozo, Carmen González-Olmedo, Alicia Cano-Jimenez, Andrea Zapater- Moros, Leticia Díaz-Beltrán, Lucia Trilla-Fuertes, Mariana Díaz-Almirón, Enrique Espinosa, Pilar Zamora, Juan Angel Fresno Vara. Prediction of recurrence in triple negative breast cancer patients after receiving neoadjuvanttreatment using plasma metabolomics [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-13-07.

Abstract PO5-15-04: MammaPrint index predicts neoadjuvant chemosensitivity in patients with HR+HER2- early-stage breast cancer in the real-world evidence FLEX study

Abstract Background: Neoadjuvant chemotherapy (NCT) yields low pathologic complete response (pCR, ypT0/is ypN0) rates in hormone receptor positive (HR+), HER2- early-stage breast cancer (ESBC). Genomic signatures may predict chemosensitivity and treatment benefit better than receptor status based clinical subtyping. The 70-gene expression signature, MammaPrint (MP), classifies patients with ESBC as having a High or Low Risk of distant recurrence. In the NBRST and ISPY2 trials, further stratification of MammaPrint High Risk into High 1 (H1) or High 2 (H2) showed significantly higher pCR rates to NCT or targeted agents in MP H2 cancers compared to MP H1 tumors. We evaluated MammaPrint H1 and H2 status as a biomarker for neoadjuvant chemosensitivity in patients with HR+HER2- ESBC enrolled in the real-world evidence FLEX study. Methods: FLEX (NCT03053193) is an ongoing prospective, observational trial that has currently enrolled 12,328 patients with ESBC who were tested with MammaPrint as standard of care, with or without molecular subtyping signature, BluePrint (BP), and consented to clinically annotated full genome data collection (data locked Feb. 2023). Patients with HR+HER2-, MP High Risk tumors who received NCT (majority received AC-T) and had pCR data available were included in this analysis (n = 214). Patients were stratified into MP H1 (index 0.000 to -0.569) and H2 (index -0.570 to -1.000) groups. BP classified MP High Risk tumors into Luminal B-, HER2-, or Basal-Type. Differences in clinical characteristics and pCR rates between H1 and H2 tumors was assessed by Chi-Squared test and two-sided proportional z-test, respectively. The association between MP H1 and H2, BP subtype, and pCR was assessed using logistic regression and was adjusted for age, race, grade, T stage, N stage, and NCT regimen. Results: MammaPrint classified 142 (66%) cancers as H1 and 72 (34%) as H2 tumors. Age, menopausal status, race, tumor stage, and lymph node status were comparable between both groups. Although most H2 tumors (78%) were Grade 3, only 59% of all Grade 3 tumors were H2. Nearly all (98%) H1 tumors were Luminal B whereas for H2 tumors, 51% were Luminal B and 49% were Basal by BP classification. pCR rate was significantly higher in H2 tumors (29.2%) compared to H1 tumors (6.3%, p &amp;lt; 0.01) (Table). Basal-Type, H2 tumors (n=35) exhibited the highest pCR rate of 37.1%. Among BP Luminal B tumors, those with MP H2 tumors had a significantly higher pCR rate (21.6%) vs. MP H1 tumors (5.8%, p = 0.003). Multivariate analysis revealed MP H2 (OR=4.91, p=0.003) and BP Basal-Type (OR=3.54, p=0.03) were significantly associated with likelihood of pCR, whereas clinical variables were not associated with pCR. Conclusion: These data demonstrate MammaPrint and BluePrint utility to predict the likelihood of achieving pCR after NCT in HR+HER2- ESBC. Although both MP High Risk groups exhibit chemosensitivity, High 2 tumors have higher chemosensitivity than High 1 tumors. MP High 2 status can be utilized to identify ER+ patients who are the most likely to experience pathologic downstaging and pCR after NCT. Also, patients with High 2 tumors treated with PD-L1 or PARP inhibitors in the ISPY2 trial exhibited significantly higher pCR rates than those observed for High 2 tumors treated with NCT alone. These data suggest that for patients with MP High 2 tumors, neoadjuvant use of chemotherapy is appropriate and these patients may further benefit from the addition of targeted agents to standard NCT. Table: Distribution of pCR rates among MammaPrint H1 and H2 and BluePrint molecular subgroups Data presented as # of patients with pCR/(total # patients in subgroup) and as percentage Citation Format: Joyce O'Shaughnessy, Lajos Pusztai, Cathy Graham, Pat Whitworth, Peter Beitsch, Cynthia Osborne, Rakhshanda Rahman, Andrea Menicucci, William Audeh, FLEX Investigators' Group. MammaPrint index predicts neoadjuvant chemosensitivity in patients with HR+HER2- early-stage breast cancer in the real-world evidence FLEX study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-15-04.

Abstract CT029: Chemotherapy-free neoadjuvant regimen with durvalumab, trastuzumab and pertuzumab (DTP) in HER2-enriched early breast cancer: A prospective, open-label phase II trial

Abstract Background: High risk HER2-positive early breast cancer (EBC) patients are traditionally treated with neoadjuvant chemotherapy in combination with HER2-directed therapy. De-escalation approaches are being studied as benefits of chemotherapy in the HER2-enriched subset of EBC, but they have been inconclusive thus far. Preclinical studies suggest synergistic effect of immune checkpoint blockade (ICB) and HER2-directed therapy. This study hypothesizes that biologically directed HER-2 targeted therapy with Trastuzumab (T) and Pertuzumab (P) together with ICB (Durvalumab, D) will obviate the need of chemotherapy in HER2-enriched EBC patients. Methods: In this single arm, open-label phase II study, previously untreated, stage I-III, ER/PR negative, HER2-enriched breast cancer (BluePrint®, Agendia) patients were treated with D (1120mg IV, q3w), T (8mg/kg IV loading dose, 6 mg/kg IV q3w), and P (840 mg IV loading dose, 420 mg IV q3w) for 6 cycles. Response was assessed at end of 6 cycles with breast MRI and possible biopsy if residual disease was present. Responders (MRI and/or biopsy negative for residual cancer) proceeded to surgery, while patients with biopsy-proven residual disease were offered salvage standard chemotherapy (TCHP) before surgery. Primary end-point was pathological response rate defined as residual cancer burden (RCB)-0 and RCB-1. Patients who achieved RCB 0/1 received adjuvant DTP for 1 year. Results: A total of 51 patients were screened; 39 patients have been enrolled and received at least one cycle of treatment. Of these, 35 patients are evaluable for pathologic response, and 2 patients are still receiving treatment. One patient died of unrelated myocardial infarction, and one patient was lost to follow-up. The median age was 55 years (range 29-85). Thirty-one (79.5%) patients were white; 4 (10.3%) African American, and 4 (10.3%) Asian. Twenty-nine (74.3%) patients had &amp;gt;=T2 tumors; 21 (53.8%) patients had N1/N2/N3 disease. Six patients (15.3%) had biopsy-proven residual disease after DTP therapy, and they received salvage standard neoadjuvant TCHP chemotherapy. The combination was well tolerated; 5 (18.8%) patients had G3-4 adverse events. Twenty-seven of thirty-five patients (77.1%) had pathologic RCB 0/1 (RCB0, 20/35; RCB1 7/35), of whom only 3 patients had received salvage chemotherapy. Correlative studies, including tumor-infiltrating lymphocytes, immune-related gene signatures and PD-L1 expression are underway. Conclusions: Chemotherapy-free neoadjuvant regimen with DTP in HER2-enriched EBC showed high pathologic response rates comparable to that with chemotherapy. This DTP regimen may provide an effective, relatively non-toxic, and biologically driven alternative to standard of care chemotherapy in this HER2-enriched subset of EBC. Citation Format: Jian Guan, Kai Sun, Dharamvir Jain, Sunil Mathur, Hanh Mai, Polly Niravath, Jenny Chang. Chemotherapy-free neoadjuvant regimen with durvalumab, trastuzumab and pertuzumab (DTP) in HER2-enriched early breast cancer: A prospective, open-label phase II trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT029.

Abstract CT085: Targeting androgen signaling in urothelial carcinoma

Abstract Background: Men are 3-4 times more likely to develop urothelial carcinoma (UC) than women, even after accounting for differences in smoking and occupational exposures. A potential cause for this difference may be androgen signaling. Testosterone receptors are present in up to 53% of UC in men and women. Androgen signaling promotes proliferation and chemotherapy resistance, while blocking androgen has been shown to sensitize UC to chemotherapy. When exposed to a chemical carcinogen, castrated male mice and androgen receptor (AR) knockout mice are less likely to develop UC. Additionally, men taking testosterone lowering agents for prostate cancer, who are concurrently treated for UC, have a 50% lower UC recurrence rate than men with normal testosterone signaling. In a study of 9 men and 1 woman with metastatic UC, all patients were treated with gemcitabine/cisplatin and concurrent enzalutamide. Patients’ testosterone levels were not medically lowered. Importantly, dihydrotestosterone, the native ligand for the AR, has higher affinity for the AR than enzalutamide. Interestingly, the only woman in the study (with presumably low dihydrotestosterone levels) had a complete response to therapy. No other complete responses were observed. The standard therapy for non-metastatic muscle invasive UC is chemotherapy followed by cystectomy. Currently this results in about a 35% pathologic complete response (pCR) rate. pCR is associated with improved overall survival. In our study (TASUC; NCT05839119), we add degarelix to standard neoadjuvant chemotherapy to treat men and women who have AR positive UC. Methods: The main eligibility criteria are: (1) Muscle-invasive urothelial carcinoma of the bladder (2) AR positive disease by nuclear staining on immunohistochemistry (3) pT2 - T4, N0 - N1, M0 (Stage II or IIIA disease) (4) Eligible for cisplatin-based chemotherapy (5) Eligible for cystectomy In this single-arm study, all patients receive standard of care gemcitabine/cisplatin neoadjuvant chemotherapy (4 cycles) with the addition of monthly degarelix during chemotherapy. The primary outcome is pCR rate at cystectomy. We are employing a Simon 2-stage minmax design. In stage I we will enroll 20 patients. If there are at least 7 pCRs (35%) we will enroll an additional 12 patients in stage II, for a total of 32 patients. This design will provide 80% statistical power to detect a change in pCR rate from 35% to 50% with a significance level of less than 0.20. If we observe at least 14 pCRs (of 32 patients) the study will be considered positive and we will plan a follow-up randomized, controlled phase II (or phase III) study. Exploratory outcomes include correlation of AR positivity with proliferation at diagnosis, identification of oncogenic androgen response elements from matched pre- and post- treatment tissue, and identification of gene signatures associated with pCR. We will also measure 2- and 5-year disease free survival. TASUC opened to accrual on October 2, 2023 and is actively recruiting. Citation Format: Mojisola Araoye, Anthony Mega, Galina G. Lagos, Benedito Carneiro, Sari Khaleel, Dragan Golijanin, SHELDON L. HOLDER. Targeting androgen signaling in urothelial carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT085.