Mixed Histology Research Articles

Abstract 4632: Lineage plasticity as a determinant of antibody-drug conjugate target expression in urothelial bladder cancer

Abstract Bladder cancers display a wide spectrum of morphologies that frequently co-exist within individual tumors. Several histologic variants, including plasmacytoid, neuroendocrine, and micropapillary subtypes, are associated with an increased bladder cancer recurrence risk and cancer-specific mortality. The molecular basis and therapeutic implications of this phenotypical plasticity remain poorly understood. Enfortumab vedotin (EV), an antibody-drug conjugate targeting Nectin-4, has also emerged as a new standard-of-care for metastatic bladder cancer patients, but the association between lineage plasticity as manifested by morphologic heterogeneity in bladder cancer, Nectin-4 expression and ADC response remains poorly defined. Previous DNA-based molecular profiling studies of histologic variants revealed that CDH1 mutations were the pathognomonic molecular alteration in plasmacytoid urothelial carcinoma, but no recurrent driver mutations have been found to be unique to the aberrant histology regions of other mixed histology subtypes. Thus, to explore the molecular basis for the lineage plasticity of bladder cancers with aberrant histology and to define the association between lineage plasticity manifested as morphologic heterogeneity and the expression of Nectin-4, HER2 and other potential ADC targets, we performed RNA-seq of pure urothelial carcinomas (n=118, not otherwise specified, UC-NOS) and bladder tumors with divergent differentiation or histologic subtypes (n=199). Our cohort included a subset of tumors in which RNA-seq was performed on microdissected UC-NOS and variant histology regions of the same tumor. Tumors with neuroendocrine, sarcomatoid and squamous histology had the lowest Nectin-4 expression, whereas histologic subtypes that retained a luminal transcriptional profile such as micropapillary, plasmacytoid and nested histology had higher levels of Nectin-4 expression. In mixed histology tumors, Nectin-4 and/or HER2 expression was often restricted to only one of the two histologic components. Gene Set Enrichment Analysis noted enrichment of distinct oncogenic pathway gene sets in different histologic variants. Preliminary investigation into the mechanism(s) of Nectin-4 regulation using bladder cancer cell lines and patient-derived organoids (PDOs) has identified targetable pathways which when inhibited revert lineage plasticity and induce Nectin-4 expression. In sum, lineage plasticity manifested as heterogenous histomorphologies was associated with heterogeneous Nectin-4 expression in some but not all histologic variants of bladder cancer. Ongoing studies using PDOs from bladder cancer patients with mixed histology will seek to identify molecular pathways whose inhibition leads to increased expression of Nectin-4 or other ADC targets such as HER2 and thus increased sensitivity of ADCs targeting these cell surface proteins. Citation Format: Jiaqian Luo, Sizhi P. Gao, Fengshen Kuo, Gamze Gokturk Ozcan, Merve Basar, Florestan Koll, Jacob E. Tallman, Syed M. Alam, Carissa E. Chu, Ziyu Chen, Eugene J. Pietzak, Gopakumar Iyer, Jonathan E. Rosenberg, David B. Solit, Hikmat Al-Ahmadie. Lineage plasticity as a determinant of antibody-drug conjugate target expression in urothelial bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4632.

High Expression of WT1 and Low Expression of p53 in Archived Blocks of Children with Wilms Tumor in South Western Uganda.

The determination of the presence or absence of anaplasia in Wilms tumor is difficult sometimes creating diagnostic errors and is worsened by the use of neoadjuvant chemotherapy, which causes cellular alterations that may mimic anaplasia. This study described the histological features of Wilms tumor and their association with WT1 and p53 expression in archived specimens in South Western Uganda. A series of 308 formalin-fixed paraffin-embedded tissue blocks belonging to 85 children were retrospectively recruited in the only public Histopathology laboratory in South Western Uganda. Rabbit monoclonal Anti-Wilms tumor protein antibody [(CAN-R9) IHC-56-2] ab89901 and rabbit monoclonal Anti-p53 antibody [E26] ab32389 were used to assess the expression of WT1 and p53, respectively. The expression of WT1 and p53 were reported as proportions, Chi-square was also performed to assess for associations and statistical significance was considered when the p-value was less than 0.05. The median age was 3.5 with an interquartile range of (2-6) years. Mixed histology was the most common at 35.29% (95% CI:25.77-46.14). Anaplasia was present in 5.88% (95% CI:2.44-13.52) of the specimens. p53 and WT1 expressions were 13.0% (95% CI:7.25-22.04), and 41.0% (95% CI: 31.11-52.04), respectively. Mixed-type histology is the most common histologic feature of Wilms tumor with high expression of WT1 and a low expression of p53 implying that these can be used routinely to confirm the diagnosis as well as anaplasia in South Western Uganda.

Abstract B022: Conversion from minimally invasive surgical approaches to open surgery among endometrial cancer patients in a national cancer patients’ registry

Abstract Endometrial cancer (EC) ranks as the predominant gynecological malignancy in the US. While minimally invasive surgical (MIS) techniques have revolutionized EC management, conversion to laparotomy remains a concern, with reported rates varying widely. Factors influencing this conversion, including patient characteristics and tumor attributes, have not been fully understood. Addressing this gap, our study employs a national registry to analyze patient, tumor, and surgeon-related factors contributing to the transition from MIS to laparotomy in EC cases. Results: 0ur results showed, 3.4% (135/4028) experienced planned MIS-to-open conversion. Demographic disparities were absent between conversion and MIS groups. Conversion was more prevalent in obese (29%) and morbidly obese (37%) patients (P=0.04), linked to prior abdominal surgery (63% vs 52%; P=0.001). Endometrioid EC predominated (59%) in the converted group, with higher non-endometrioid rates (serous carcinoma 16%, clear cell carcinoma 4%, carcinosarcoma 5%, mixed histology 12%; all P<0.01). Advanced FIGO stages were more common in conversions (stage II: 5%, stage III: 25%, stage IV: 9%; all P<0.001). Type II (24%) and type III (5%) hysterectomies were more frequent in conversions (P<0.001). Logistic regression indicated BMI, prior surgery, FIGO stage, histology, and operation type affected conversion (p<0.001), explaining 12.3% of variance. Indications for conversion included uterine size, adhesions, and disease extent. Conclusion: the adoption of minimally invasive surgery (MIS) has become increasingly popular for managing endometrial cancer (EC), attributed to enhanced perioperative outcomes. However, prudent patient selection and surgical planning are imperative to mitigate the risk of unplanned transition to open surgery. Predictive factors for such conversion include uterine size, prior abdominal surgeries, surgical complexity, disease extent, and histologic types. Further prospective research is warranted to validate these findings and identify individuals at conversion risk. Ultimately, a personalized surgical approach, tailored to individual patient attributes, remains pivotal for optimizing outcomes in EC management. Citation Format: Abdelrahman Yousif, Julie Ngo, Deena Abdel-Gadir, Jenny Lachance, Benjamin Mize, Ilana Chefetz. Conversion from minimally invasive surgical approaches to open surgery among endometrial cancer patients in a national cancer patients’ registry [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B022.

Performance of a tumor-informed molecular residual disease (MRD) assay in resected bladder cancer with mixed or pure variant histology: Analysis of a real-world multicenter cohort.

649 Background: Circulating tumor DNA (ctDNA)-based MRD assays can detect clinically occult disease with high sensitivity and specificity in patients with solid tumors. Previous trials that evaluated MRD testing in bladder cancer, such as ABACUS and IMVigor010, enrolled patients with a predominant urothelial carcinoma component. Given the known histological and molecular heterogeneity in urothelial carcinoma, we examined the prognostic value of a tumor-informed MRD assay in bladder cancer patients with mixed or pure variant histologies (M/VH). Methods: This retrospective study analyzed the results of post-cystectomy longitudinal ctDNA testing from a multi-institutional database of patients with urothelial carcinoma (n=205). A personalized, tumor-informed assay (Signatera, Natera, Inc.) was used for the detection and quantification of ctDNA. Patients with M/VH and at least 3 months of postoperative follow-up data on relevant demographic, clinical, pathologic, and NGS variables were eligible for inclusion. Time-dependent Cox regression analyses were performed for disease-free survival (DFS) based on ctDNA during the MRD window (<12 weeks from surgery, N=29) and surveillance window (>12 weeks post-surgery or post-AT, N=29). Multivariable regression was performed to adjust hazards for clinicopathologic factors predicting DFS. Results: Of the 205 patients, 46 (74% male, median age: 69 years) met the inclusion criteria for analysis. Whole exome sequencing of tumor tissue revealed that TP53 (45.7%), ARID1A (32.6%), and KDM6A (30.4%) were the top three genes with somatic mutations. Twenty-seven (59%) patients received neoadjuvant therapy, 37% of whom (10/27) also received adjuvant therapy. ctDNA-positivity during the MRD window and during surveillance was strongly associated with poor DFS (MRD window: HR=4.93, 95%CI: 1.77-20.77, p=0.03; surveillance: HR=28.3, 95% CI: 3.52-3660, p<0.001). None of the serially ctDNA-negative patients (N=25) recurred, whereas 58.9% (10/17) of patients who were ctDNA-positive anytime post-surgery recurred at a median follow-up of 9 months from the date of surgery, range: 3.1-36.4 months). When adjusted for all other risk factors, ctDNA-positivity anytime post-surgery was the only significant predictor of recurrence (HR=55.26, 95%CI: 5.3-7648, p<0.00001). Conclusions: Personalized, tumor-informed ctDNA testing can identify patients with mixed or variant histology bladder cancer who are at high risk of recurrence. Further studies are warranted to evaluate the potential benefit of ctDNA-guided adjuvant therapy in this patient population.

Utility of PSMA PET/CT for imaging ductal carcinoma of the prostate.

49 Background: Ductal carcinoma (DC) is the second most commonly encountered histologic variant of prostate cancer. Previous studies have described its molecular features and aggressive behavior, but few have explored the performance of PSMA PET/CT in the initial staging and follow-up of DC. Methods: To address this gap, we performed a single-institution retrospective analysis using the Mayo Clinic PSMA PET database. All patients receiving a PSMA PET/CT scan in the interval of January 1, 2021, to December 31, 2022, were eligible for inclusion. Cases were filtered and categorized by histology at the time of diagnosis to select for pure DAC and mixed ductal variants. Trained research personnel annotated disease- and treatment-related variables. A board-certified radiologist performed tumor burden segmentation with calculations of SUV max, total lesion SUV mean and volume, and total lesion uptake, and ascribed a miPSMA expression score. Results: We queried 1792 patients from our PSMA PET/CT registry and identified 32 (1.8%) patients with a pathologically confirmed DC, including 8 (25%) patients with pure ductal and 25 (75%) patients with mixed histology. The indication for PSMA PET/CT was biochemical progression or restaging for 29 (91%) patients and initial staging for 3 (9%) patients. The median (IQR) time from prostate cancer diagnosis to PSMA PET scan was 41.6 (11.5-64.7) months, during this time 50% (n= 16) of patients developed CRPC. At the time of the PSMA PET/CT scan, the median age was 70 years, the median (IQR) PSA was 0.5 ng/mL (0.2-2.6). The distribution of metastatic spread and quantitative imaging parameters from PSMA PET are shown in the Table. Conclusions: Despite low PSA at the time of imaging, PSMA PET/CT frequently detected high volume osseous and/or visceral metastases in patients with DC. However, it is noteworthy that more than 50% of patients with DC had a low miPSMA score (0-1). Additional studies are needed to better understand the performance of novel imaging modalities when evaluating variant prostate cancers. [Table: see text]

Choice of surgery in intestinal-type adenocarcinoma of the sinonasal tract: a long-term comparative study.

Intestinal-type adenocarcinoma (ITAC) is a rare sinonasal malignancy. Curative treatment requires multidisciplinary approach, with surgical options consist of the endonasal endoscopic approach (EEA) and external surgery (EXTS). Here, we provide the post-operative and survival results from a single-center long-term follow-up. We report long-term follow-up of 92 ITAC cases treated between 1998 and 2018, treated with EEA (n = 40) or EXTS (n = 52). Survival estimates, post-operative complications and duration of hospitalization were compared between surgical modalities. Baseline characteristics were similar. A higher number of T4b tumors (16%), and subsequently more tumoral invasion (39%), was present in patients undergoing EXTS compared to EEA (3% and 18%, respectively). No difference in Barnes histology subtypes was noticed. Patients undergoing EEA had a shorter post-operative hospitalization stay versus EXTS (4 versus 7days). Use of EEA was associated to improved disease-specific survival (DSS; 11.4 versus 4.4years; HREEA = 0.53), especially for patients with T3-4a tumors (11.4 versus 3.0years; HREEA = 0.41). Patients with T3-4 stage, tumoral invasion, positive surgical margins, mucinous or mixed histology, and prolonged post-operative hospital stay showed poor local relapse-free, disease-free, overall, and DSS. Long-term follow-up in locally advanced ITAC demonstrates that resection by EEA is correlated with improved DSS compared to EXTS, especially for T3-4 tumors. No significant differences between both treatment modalities was observed regarding per- and post-operative complications, although hospitalization in patients undergoing EEA was shorter than for patients treated with EXTS. These results confirm that EEA should remain the preferred surgical procedure in operable cases of sinonasal ITAC.

Abstract LB_A16: DareonTM-5: An open-label Phase II trial of BI 764532, a DLL3-targeting T cell engager, in patients with relapsed/refractory small cell lung cancer or other neuroendocrine carcinomas

Abstract Background: Small cell lung cancer (SCLC), extra-pulmonary neuroendocrine carcinomas (epNECs) and large cell NECs (LCNECs) of the lung are difficult-to-treat, aggressive tumors with limited treatment (Tx) options. Standard of care for metastatic disease is platinum-based chemotherapy ± immunotherapy. However, nearly all patients (pts) relapse, and outcomes are poor. Hence, alternative therapies are needed. Delta-like ligand 3 (DLL3), a Notch ligand, is highly expressed on the cell surface of SCLCs, epNECs and LCNECs. BI 764532, a humanized IgG-like T cell engager, binds to DLL3-positive tumor cells and CD3 on T-cells and promotes T cell-mediated cytotoxicity. In an ongoing first-in-human trial, BI 764532 exhibited promising efficacy and manageable tolerability in pts with DLL3-positive SCLC, epNEC and LCNEC of the lung (NCT04429087). Here we describe a planned Phase II dose optimization trial to assess safety/efficacy of two different doses of BI 764532 monotherapy in pts with progressive/recurrent SCLC, epNEC or LCNEC of the lung (NCT05882058). Methods: The trial will recruit adult pts (n = ~120; ~70 sites; ~15 countries) with histologically/cytologically confirmed relapsed/refractory SCLC, epNEC or LCNEC of the lung who have received ≥2 (SCLC) or ≥1 (epNEC/LCNEC) prior lines of therapy, including ≥1 platinum-based regimen. Pts with mixed tumor histology are permitted if the SCLC/NEC component is predominant (≥50% of tumor tissue). Pts will be randomized 1:1 to receive one of two dose levels of intravenous BI 764532 (3-week cycles) stratified by tumor type (n ~ 60/arm). Tx will continue until disease progression, undue toxicity, withdrawal of consent or any other documented criteria for stopping Tx (maximum Tx duration: 36 months). Interim analyses for dose selection are planned after 30 pts have been followed for ≥6 and ≥12 weeks or have stopped Tx. A third interim efficacy analysis will be conducted when 60 pts per dose have been followed for ≥12 weeks or have stopped Tx. Key exclusion criteria: ECOG PS ≥2; untreated/symptomatic brain metastases or leptomeningeal disease; active/previous history of interstitial lung disease/pneumonitis; previous Tx with DLL3-targeting therapies; Tx with other anti-cancer drug <4 weeks prior to first administration of BI 764532; unresolved toxicity from prior anti-tumor Tx; diagnosis of immunodeficiency, or intake of immunosuppressive therapy ≤7 days prior to first administration of BI 764532. Primary endpoints: objective response (RECIST v1.1; investigator assessment); occurrence of Tx-emergent adverse events (TEAEs) during the on-Tx period. Secondary endpoints: duration of objective response; progression-free survival; disease control; overall survival; pt-reported outcomes; TEAEs leading to discontinuation during the on-Tx period. Further endpoints: pharmacokinetics (PK); prespecified and exploratory biomarker analysis (archival tumor tissue is required). The comparison of the two target doses in this trial will be based on the totality of data, including safety, efficacy, PK and biomarker data. Citation Format: Valentina Gambardella, Alastair Greystoke, Martin Reck, Meiruo Liu, Martha Mueller, Ulrich Duenzinger, Emily B Bergsland, Taofeek Owonikoko. DareonTM-5: An open-label Phase II trial of BI 764532, a DLL3-targeting T cell engager, in patients with relapsed/refractory small cell lung cancer or other neuroendocrine carcinomas [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_A16.

Evaluation of the m7-FLIPI in Patients with Follicular Lymphoma: FOXO1 Mutational Status May be a Predictive Marker of Early Progression and Long-Term Outcome

DISCUSSION In pts with follicular lymphoma (FL) who received chemoimmunotherapy (CIT) as first-line treatment, progression of disease within 24 months of diagnosis (POD24) was associated with increased risk of death (Casulo, 2015). A clinicogenetic risk model that includes the mutation status of 7 genes ( EZH2, ARID1A, MEF2B, EP300, FOXO1, CREBBP, and CARD11), FLIPI and ECOG, known as the m7-FLIPI, was shown to improve risk stratification in frontline pts with advanced stage FL treated with CIT (Pastore, 2015), as well as predict POD24 after first-line CIT (Jurinovic, 2016). With the hypothesis that there are distinguishing features in the mutational landscape between pts with FL who experience POD24 vs those who don't, we evaluated the prognostic utility of the m7-FLIPI and its components in a retrospective series. MSK-IMPACT Heme (Ptashkin, 2019) is a 468 targeted gene panel that includes the 7 genes required to calculate the m7-FLIPI. We identified all pts with FL, grade 1-3A, who had IMPACT testing, excluding pts with FL grade IIIB, mixed histology, or de novo transformation at diagnosis (n = 295). Three pts were excluded for inadequate clinical data (n = 292). The m7-FLIPI was calculated as previously described. Progression-free survival (PFS) was calculated from date of diagnosis till date of progression after first-line treatment, death, or censored at date of last follow-up. Overall survival (OS) was calculated from date of diagnosis till death or censored at date of last follow-up. Cox proportional hazard models were used to compare differences in survival and the Fisher's exact test for categorical variables in SAS 9.4. A cohort of 292 pts was analyzed. Genomic alterations were identified in the 7 genes . Median age of diagnosis was 57 years (range 26-92) with a slight male predominance (53%). The median follow-up was 5.2 years (95% CI, 4.6-5.7). Initial treatment included monoclonal antibody + chemotherapy (57%), single-agent rituximab (17%), chemotherapy (2%), radiotherapy alone (8%), and other treatments (5%). Thirty-four pts (12%) were never treated. Out of 292 pts, 86 (29%) were high-risk by FLIPI and 42 (14%) were high-risk m7-FLIPI. Forty-four out of 86 pts with high-risk FLIPI (51%) were reclassified as low-risk by the m7-FLIPI. High-risk FLIPI was associated with shorter PFS (HR 1.54, 95% CI 1.12 - 2.11, p = 0.0085) and OS (HR 3.73, 95% CI 1.74 - 7.98, p = 0.0007). High-risk m7-FLIPI was associated with shorter PFS (HR 1.55, 95% CI 1.05 - 2.28, p = 0.027) but not OS (HR 2.09, 95% CI 0.92 - 4.76, p = 0.08). C-statistics showed that m7-FLIPI did not outperform FLIPI alone as a prognostic tool for PFS (FLIPI c-statistic = 0.55, 95% CI 0.51 - 0.59; m7-FLIPI c-statistic = 0.53, 95% CI 0.50 - 0.56) or OS (FLIPI c-statistic = 0.68, 95% CI 0.58 - 0.78; m7-FLIPI c-statistic = 0.55, 95% CI 0.47 - 0.63). Mutations in ARID1A as a single factor were associated with shorter PFS (HR 1.52, 95% CI 1.01-2.29, p=0.047), but this association did not remain significant after adjusting for FLIPI and ECOG (HR 1.49, 95% CI 0.97-2.28, p=0.07). Mutations in FOXO1 were associated with shorter PFS (HR 1.48, 95% CI 1.00-2.19, p=0.049) and OS (HR 2.65, 95% CI 1.21-5.79, p=0.015) as a single factor. This association remained significant after adjusting for FLIPI and ECOG: PFS (HR 1.60, 95% CI 1.08-2.37, p=0.020) and OS (HR 2.65, 95% CI 1.21-5.83, p=0.015; Table 1). High-risk m7-FLIPI and FLIPI pts were not more significantly likely to experience POD24, OR 1.44, 95% CI 0.73-2.83, p=0.37 for m7-FLIPI and 1.48, 95% CI 0.87-2.51, p=0.17 for FLIPI. Pts with mutated FOXO1 were more likely to experience POD24, OR 2.47, 95% CI 1.29-4.71, p=0.008. The m7-FLIPI neither improved risk stratification compared to FLIPI nor did it predict POD24 in this series. Mutations in FOXO1 were associated with shorter PFS and OS independent of FLIPI and ECOG. Pts with mutated FOXO1 were enriched among those with POD24, suggesting that FOXO1 mutation may be a predictive marker for early failure of first-line treatment and death, including pts not fulfilling the POD24 criteria. Similar negative impact of FOXO1 was reported in a comprehensive genomic analysis of FL (Mozas, 2023). Both series are limited by patient numbers. Additional efforts to confirm this observation may be useful for understanding the mechanisms behind the prognostic effect of POD24 on survival and improving long-term outcome in this high-risk FL group.

Prevalence of thyroid gland tissue in midline neck dermoid cysts in children and a proposed new 'thyroglossal entrainment' hypothesis for their formation.

Thyroglossal duct cysts and dermoid cysts both commonly present as midline neck lumps in children. They are treated as separate entities with different embryological origins. There are isolated reports of thyroid gland tissue in a dermoid cyst, concurrent thyroglossal and dermoid cysts, and cysts with mixed histology. It is not known if these are rare or common. All children undergoing excision of a congenital midline neck cyst between January 2017 and December 2022 were identified. Histopathology slides were reviewed in detail. In 53 children, there were 26 thyroglossal duct cysts, 24 dermoids, 1 lymph node and 2 with no diagnostic material identified. Five dermoids (28 per cent) had associated thyroid gland tissue, and 1 (4 per cent) had hybrid histology with keratinising and respiratory epithelium. Infection occurred in 17 per cent of dermoids prior to excision and 8 per cent of dermoids recurred after excision. Hybrid histology, infection and recurrence are all common in midline neck dermoids. A new theory for their embryological origin is proposed, with the suggestion that some may need more extensive surgery.

Neuroendocrine prostate tumors: histologic features and therapy

Neuroendocrine (NE) tumors of the prostate are rare tumors, that can arise de novo but much more commonly occur after androgen deprivation therapy for prostate adenocarcinoma. NE tumors of the prostate are classified into: adenocarcinoma with NE differentiation, well-differentiated NE tumor/carcinoid, small-cell NE carcinoma, large cell NE carcinoma, adenocarcinoma with Paneth cell NE differentiation and mixed NE carcinoma—acinar adenocarcinoma. IHC plays a vital role and should be approached at two levels. For the issue of confirming NE differentiation, markers for NE differentiation include synaptophysin, chromogranin, and CD56. If there is any uncertainty about the histogenesis, that is, whether a tumor is primary to the prostate, markers for prostatic lineage—PSA, PSAP, PSMA, prostein (p501s), NKX3.1, ERG (by IHC or FISH)—may be used. Actually, platinum-based chemotherapy is commonly administered to patients with pure small cell carcinoma based on small cell lung cancer (SCLC) data and the accumulating data for aggressive variants of castration-resistant prostate cancer (AVPC). This may consist of a combination of carboplatin (or sometimes cisplatin) plus either etoposide (based on SCLC) or a taxane (especially if mixed histology or AVPC features). A combination regimen of cisplatin, etoposide, and doxorubicin has been also investigated but the benefit-risk ratio of the three-drug combination was considered unfavorable. Unfortunately, platinum-based chemotherapy often presents high toxicity and a short overall survival. Results of currently ongoing preclinical and clinical studies are expected to enhance our understanding of these tumors’ underlying biology and guide our efforts toward the development of personalized medicine through targeted diagnostic and therapeutic approaches.

Molecular classification of mixed histology endometrial cancers (1301)

Molecular classification of mixed histology endometrial cancers (1301)

Pathologic Features, Treatment, and Clinical Outcomes of Lacrimal Gland Cancer.

Lacrimal gland cancer is a rare malignancy with little data known about its pathologic characteristics or optimal management. We performed a large database analysis using the National Cancer Database (NCDB) to elucidate this unusual condition. Patients with lacrimal gland cancer diagnosed between 2004 and 2018 were included in the analysis. Using available clinical data, we excluded all patients with histologies likely reflective of lacrimal sac or duct cancer, which are coded similarly to lacrimal gland cancer in the NCDB. Kaplan-Meier analysis was used to estimate overall survival (OS), and Cox proportional hazards models were used to indicate covariates associated with survival. A total of 440 cases of lacrimal gland cancer were included in the analysis, with a median follow-up of 52.9 months. The five-year OS for the entire cohort was 65.0%. Adenoid cystic carcinoma was the predominant histology (47.3%). Cox models showed that improved OS was associated with surgical resection (UVA: p < 0.001; MVA: p = 0.035). A detriment in OS was associated with increasing age, Charlson-Deyo score of 1, T4 stage, and positive margins and on UVA for adenocarcinoma and malignant mixed tumor histology. Adenoid cystic carcinoma comprises the plurality of lacrimal gland cancers. About half of patients with lacrimal gland carcinoma will live beyond 10 years, underscoring the importance of reduced morbidity of treatment. Surgical management is associated with improved prognosis. Further study will elucidate the role of surgical excision and radiotherapy in lacrimal gland cancer.

Genomic Profiling Reveals Germline Predisposition and Homologous Recombination Deficiency in Pancreatic Acinar Cell Carcinoma.

To determine the genetic predisposition underlying pancreatic acinar cell carcinoma (PACC) and characterize its genomic features. Both somatic and germline analyses were performed using an Food and Drug Administration-authorized matched tumor/normal sequencing assay on a clinical cohort of 28,780 patients with cancer, 49 of whom were diagnosed with PACC. For a subset of PACCs, whole-genome sequencing (WGS; n = 12) and RNA sequencing (n = 6) were performed. Eighteen of 49 (36.7%) PACCs harbored germline pathogenic variants in homologous recombination (HR) and DNA damage response (DDR) genes, including BRCA1 (n = 1), BRCA2 (n = 12), PALB2 (n = 2), ATM (n = 2), and CHEK2 (n = 1). Thirty-one PACCs displayed pure, and 18 PACCs harbored mixed acinar cell histology. Fifteen of 31 (48%) pure PACCs harbored a germline pathogenic variant affecting HR-/DDR-related genes. BRCA2 germline pathogenic variants (11 of 31, 35%) were significantly more frequent in pure PACCs than in pancreatic adenocarcinoma (86 of 2,739, 3.1%; P < .001), high-grade serous ovarian carcinoma (67 of 1,318, 5.1%; P < .001), prostate cancer (116 of 3,401, 3.4%; P < .001), and breast cancer (79 of 3,196, 2.5%; P < .001). Genomic features of HR deficiency (HRD) were detected in 7 of 12 PACCs undergoing WGS, including 100% (n = 6) of PACCs with germline HR-related pathogenic mutations and 1 of 6 PACCs lacking known pathogenic alterations in HR-related genes. Exploratory analyses revealed that in PACCs, the repertoire of somatic driver genetic alterations and the load of neoantigens with high binding affinity varied according to the presence of germline pathogenic alterations affecting HR-/DDR-related genes and/or HRD. In a large pan-cancer cohort, PACC was identified as the cancer type with the highest prevalence of both BRCA2 germline pathogenic variants and genomic features of HRD, suggesting that PACC should be considered as part of the spectrum of BRCA-related malignancies.

Neuroendocrine carcinoma of the cervix: A comprehensive clinicopathologic study and literature review

AimsNeuroendocrine carcinoma of the cervix (NECC) is a rare variant of cervical cancer. This study aims to investigate the clinicopathological features and prognosis of NECC. MethodsA retrospective analysis was conducted on twenty-one patients diagnosed with NECC between May 2008 and September 2021 ​at Peking University People's Hospital. The study involved histopathological examination, immunohistochemistry, ThinPrep cytology test (TCT), and high-risk HPV hybrid capture 2 (HC2) assay. Follow-up was conducted through telephone interviews and medical records for a range of 3–160 months, with an average follow-up period of 49.8 months. ResultsThe average age of the patients was 48.6 years (range: 33–69 years). Seventeen patients were diagnosed with neuroendocrine carcinoma through biopsy. Nine cases underwent TCT and HC2 tests before biopsy, and TCT results of four cases showed high-grade squamous intraepithelial lesion (HSIL). High-risk HPV(HR-HPV) positive was detected in seven cases. The cancer cells exhibited consistent morphological features, including sparse cytoplasm, intensely stained nuclei, and extensive neoplastic necrosis. Thirteen cases were classified as pure NECC (61.9%), while eight cases were mixed types (38.1%). Three cases were associated with squamous cell carcinoma (SCC), and five cases were associated with adenocarcinoma. Prognosis varied significantly among these subtypes (p ​< ​0.05). The overall survival rate in the follow-up period was 66.7% (12/18). ConclusionsNECC is an extremely rare and highly aggressive tumor with a poor prognosis, particularly in cases of mixed histology. It is strongly associated with HPV infection. TCT and HPV testing significantly enhance the detection rate before the biopsy. The diagnosis of NECC relies on histological and immunohistochemical examinations. This study provides valuable clinical observations on NECC and emphasizes the importance of early detection and accurate diagnosis for improved patient outcomes.

KRAS(G12D) drives lepidic adenocarcinoma through stem-cell reprogramming.

Many cancers originate from stem or progenitor cells hijacked by somatic mutations that drive replication, exemplified by adenomatous transformation of pulmonary alveolarepithelial type II (AT2) cells1. Here we demonstrate a different scenario: expression of KRAS(G12D) in differentiated AT1 cells reprograms them slowly and asynchronously back into AT2 stem cells that go on to generate indolent tumours. Like human lepidic adenocarcinoma, the tumour cells slowly spread along alveolar walls in a non-destructive manner and have low ERK activity. We find that AT1 and AT2 cells act as distinct cells of origin and manifest divergent responses to concomitant WNT activation and KRAS(G12D) induction, which accelerates AT2-derived but inhibits AT1-derived adenoma proliferation. Augmentation of ERK activity in KRAS(G12D)-induced AT1 cells increases transformation efficiency, proliferation and progression from lepidic to mixed tumour histology. Overall, we have identified a new cell of origin for lung adenocarcinoma, the AT1 cell, which recapitulates features of human lepidic cancer. In so doing, we also uncover a capacity for oncogenic KRAS to reprogram a differentiated and quiescent cell back into its parent stem cell en route to adenomatous transformation. Our work further reveals that irrespective of a given cancer's current molecular profile and driver oncogene, the cell of origin exerts a pervasive and perduring influence on its subsequent behaviour.

Abstract PR004: Exploring the role of ASCL1 in neuroendocrine prostate cancer

Abstract Most patients with prostate adenocarcinoma (PAd), an androgen receptor (AR) driven cancer, develop resistance to therapies targeting AR. Consequently, a portion of these patients develop neuroendocrine prostate cancer (NEPC), a rapidly progressing cancer with limited therapies and poor survival outcomes. Current research to understand the transition of PAd to NEPC suggests a model of lineage plasticity, where AR-dependent luminal tumors progress towards an AR-independent neuroendocrine lineage. Several groups have shown human NEPC tumors have lost RB1 and TP53, and in experimental models, loss of both genes mediates the transition to a neuroendocrine lineage. Notably, NEPC histology and gene expression resemble another neuroendocrine cancer, small cell lung carcinoma (SCLC), also characterized by loss of RB1 and TP53. In SCLC, transcription factor ASCL1 is required for tumor cell growth in vitro and for SCLC formation in vivo. ASCL1 is also present in NEPC tumors and in NEPC cell line models. In fact, ASCL1 was shown to regulate neuronal stem cell-like lineage programming in NEPC in vitro. We aimed to determine if ASCL1 is required in the transition of PAd to NEPC in vivo and to define its function in NEPC. To model the PAd to NEPC transition, we established genetically engineered mouse models (GEMMs) harboring loss of RB1 and TP53 with MYC overexpression (RPM) by administering adenovirus expressing Cre recombinase directly to the prostate of these GEMMs. These animals display prostate tumors with small cell histology and are heterogeneous for neuroendocrine markers such as ASCL1, NEUROD1, and INSM1. We recently determined that the concomitant loss of ASCL1 in this model (RPMA) does not stop the formation of tumors with small cell histology. Notably, a subset of the cells with small cell histology are NEUROD1+, with a higher proportion of NEUROD1+ cells present compared to the RPM model with intact ASCL1, suggesting the possibility that NEUROD1 in the same or distinct cells is compensating for the absence of ASCL1. In a separate paradigm using these same GEMMs to establish prostate organoids, we show their capacity to generate subcutaneous allograft tumors displaying mixed histology including neuroendocrine small cell features expressing ASCL1, NEUROD1, and INSM1. Strikingly, subcutaneous allografts from prostate organoids lacking ASCL1 exhibit a dramatic reduction in tumor formation efficiency, lack small cell histology including NEUROD1 and INSM1 and other neuroendocrine markers, and often result in the development of cysts rather than tumors. These results demonstrate complex functions for ASCL1 in neuroendocrine lineage programming while suggesting additional functions in supporting prostate tumor formation. Citation Format: Kathia E. Rodarte, Lydia Flores, Vishal Kandagatla, Juan Villarreal, Trisha K. Savage, Su Deng, Ping Mu, Rajal B. Shah, Trudy G. Oliver, Jane E. Johnson. Exploring the role of ASCL1 in neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr PR004.

Impact of histology on the efficacy and safety of pembrolizumab (pembro) monotherapy for advanced urothelial carcinoma (UC) in the phase 3 KEYNOTE-045 and KEYNOTE-361 trials.

4512 Background: For patients (pts) with advanced UC, pembro monotherapy has shown antitumor activity as first-line (1L) therapy in the phase 3 KEYNOTE-361 (NCT02853305) study of pembro ± platinum-based chemotherapy (chemo) vs platinum-based chemo and as second-line therapy in the phase 3 KEYNOTE-045 (NCT02256436) study of pembro vs investigator’s choice chemo. This exploratory analysis evaluated efficacy and safety of pembro monotherapy by UC histology in KEYNOTE-361 and KEYNOTE-045. Methods: KEYNOTE-361 enrolled pts with advanced UC and no prior systemic therapy; KEYNOTE-045 enrolled pts with advanced UC whose disease progressed or relapsed after 1L platinum-based chemo. Pure transitional cell (TC) and mixed predominant TC histology, as assessed by investigator, were allowed. Pembro monotherapy was given at a dose of 200 mg IV Q3W for up to 2 y or until disease progression, unacceptable toxicity, or withdrawal of consent in both studies. End points for this exploratory analysis were ORR, DOR, and PFS per RECIST v1.1 by central radiology assessment, and OS and safety in pts with pure TC or mixed predominant TC allocated to receive pembro monotherapy. Results: A total of 307 randomly assigned pts (280 [91.2%] pure TC histology; 27 [8.8%] mixed predominant TC histology) from KEYNOTE-361 and 268 pts (186 [69.4%] pure TC histology; 82 [30.6%] mixed predominant TC histology) from KEYNOTE-045 were included. Median follow-up for both studies was ≥32 mo. PFS, ORR, DOR, and OS for pembro were generally similar in pts with mixed predominant TC histology and pts with pure TC histology. In treated pts, grade 3-5 treatment-related AEs occurred at similar rates in KEYNOTE-361 (17.3% [48/277] pure TC; 18.5% [5/27] mixed predominant TC) and KEYNOTE-045 (16.9% [31/183] pure TC; 17.3% [14/81] mixed predominant TC). Conclusions: The observed clinical activity and safety profile of pembro monotherapy was generally consistent irrespective of histology in pts with UC in the KEYNOTE-361 and KEYNOTE-045 studies. Small sample size in some subgroups and limited data available to classify histology subgroups were limitations of this exploratory analysis. Clinical trial information: NCT02256436; NCT02853305 . [Table: see text]

Prevalence of STK11, KEAP1, and KRAS mutations/co-mutations and associated clinical outcomes for patients newly diagnosed with metastatic non-small cell lung cancer.

e21186 Background: Data on the prevalence of emerging mutations /co-mutations (e.g., STK11, KRAS, and KEAP1) and associated clinical outcomes in metastatic non-small cell lung cancer (mNSCLC) patients are lacking therefore the objective of this study is to address these gaps in the current data. Methods: This study used the Flatiron clinico-genomic database and included newly diagnosed patients (≥18 years old) with stage IV NSCLC and known histology/PD-L1 status. Patients enrolled in clinical trials, with positive/missing EGFR or ALK, other malignancies, mixed histology, or without structured data within 90 days of diagnosis were excluded. The prevalence of STK11, KEAP1, KRAS mutations and co-mutations for each combination were evaluated in the overall study cohort and stratified by histology and PD-L1 status ( &gt; or ≤1%). The overall survival (OS) from the date of diagnosis with stage IV was analyzed using Kaplan-Meier methods. Results: Of the 17,020 patients with NSCLC, 964 met the selection criteria and were included in the study. The prevalence of STK11, KEAP1, and KRAS is 18%, 15%, and 35%, respectively. With the exception of KRAS, the prevalence of all selected mutations and the co-mutations is higher in patients with PD-L1 negative and non-squamous NSCLC. The prevalence of KRAS is higher in patients with PD-L1 positive and non-squamous NSCLC (Table). The median OS was 10.1 months (95% CI, 8.6, 11.2) for the overall population, and 6.6 (5.7-8.3), 7.1 (5.8-8.8) and 9.9 (7.6-11.9) months in patients with STK11, KEAP1, and KRAS mutations, respectively. The median OS in patients with co-mutations ranges from 6.1 to 6.7 months. Conclusions: STK11, KEAP1, and KRAS mutations and co-mutations are common in mNSCLC patients. Current treatments, particularly in STK11, KEAP1, and co-mutation patients, are associated with poor OS. To address these harder to treat subgroups new treatment options or clinical trials should be considered. [Table: see text]

Study EV-103: Neoadjuvant treatment with enfortumab vedotin monotherapy in cisplatin-ineligible patients (pts) with muscle invasive bladder cancer (MIBC): Updated results for Cohort H.

4595 Background: Cisplatin-ineligible pts with MIBC have no established neoadjuvant treatment options known to prolong survival before undergoing radical cystectomy and pelvic lymph node dissection (RC+PLND), Enfortumab vedotin (EV) is an antibody-drug conjugate directed to Nectin-4, which is highly expressed in urothelial cancer. In a phase 3 study, EV showed improved overall survival vs standard chemotherapy and a tolerable safety profile in pts with advanced urothelial cancer previously treated with a platinum agent and a PD-1/L1 inhibitor (Powles NEJM 2021). In Cohort H of the EV-103 phase 1b/2 study, preliminary results, including pathological complete response (pCR) and pathological downstaging (pDS) rates, showed antitumor activity in cisplatin-ineligible pts with MIBC who received neoadjuvant EV treatment (Petrylak ASCO GU 2022). Here we report updated results, including event-free survival (EFS) and subsequent cancer-related therapy. Methods: Cohort H of the EV-103 phase 1b/2 study (NCT03288545) enrolled cisplatin-ineligible pts with MIBC (T2-T4aN0M0) and ECOG PS ≤2 who were eligible for RC+PLND. Pts received neoadjuvant EV (1.25 mg/kg) on Days 1 and 8 every 21 days for 3 cycles before undergoing RC+PLND. The primary endpoint was pCR rate (ypT0 and N0) by central pathology review. Key secondary endpoints included pDS rate (ypT0, ypTis, ypTa, ypT1, and N0), EFS based on investigator assessment, and safety. Results: 22 pts (median age 74.5 yr, range 56-81) were enrolled and treated; 17 pts (77.3%) remain on study. Pts had stage cT2 (68.2%), cT3 (27.3%), or cT4 (4.5%) disease. 68.2% of pts had transitional cell carcinoma only; 31.8% had a mixed histology. 86.4% of pts completed all 3 cycles of EV treatment; the median duration of EV treatment was 2.1 months (range 0.7-2.3). The pCR rate was 36.4% (95% CI, 17.2, 59.3) and the pDS rate was 50.0% (95% CI, 28.2, 71.8). Median EFS has not been reached. The EFS rate at 12 months was 76.4% (95% CI, 52.2, 89.4). All pts underwent surgery with no delays due to EV-related TEAEs. The most common EV-related TEAEs were fatigue (45.5%), dysgeusia (36.4%), and alopecia (31.8%); 18.2% of pts had grade ≥3 EV-related TEAEs. 68.2% of pts had surgery-related TEAEs and 31.8% pts had grade ≥3 surgery-related TEAEs. The most common surgery-related TEAEs were procedural pain (18.2%), anaemia (13.6%), and constipation (13.6%). 3 pts died due to AEs unrelated to EV treatment; in 2 pts the AEs occurred &gt;30 days after RC+PLND. 36.4% of pts received subsequent cancer-related therapy. Conclusions: Neoadjuvant EV monotherapy treatment showed promising results for antitumor activity and EFS with a manageable safety profile in cisplatin-ineligible pts with MIBC. These results support ongoing phase 2 and 3 programs in MIBC evaluating EV alone or combined with pembrolizumab (EV-103 Cohort L, KN-905, KN-B15). Clinical trial information: NCT03288545 .

LATIFY: Phase 3 study of ceralasertib + durvalumab vs docetaxel in patients with locally advanced or metastatic non-small-cell lung cancer that progressed on or after anti-PD-(L)1 and platinum-based therapy.

TPS9161 Background: Following progression on first- or second-line immunotherapy ± platinum-based chemotherapy (CT), the prognosis for patients (pts) with metastatic non-small-cell lung cancer (NSCLC) is poor with limited alternative options to docetaxel. Ceralasertib is a selective inhibitor of Ataxia Telangiectasia and Rad3-related (ATR) protein kinase, which is activated in response to DNA damage. Clinical data suggest that ceralasertib may sensitize tumors to immunotherapy by biasing T cells to an immune-effective phenotype. Durvalumab is a selective, high-affinity human IgG1 monoclonal antibody that binds programmed cell death ligand-1 (PD-L1) and inhibits PD-L1-mediated suppression of T-cell activation. Combining ceralasertib with durvalumab may amplify the antitumor immune response, and potentially lead to durable tumor control. In the ongoing phase 2 HUDSON study in pts with locally advanced or metastatic NSCLC who progressed on anti-PD-(L)1 therapy and platinum-doublet regimen, ceralasertib + durvalumab showed promising efficacy with median progression-free survival (PFS) of 6.0 mos (80% CI, 4.6–7.5) and median overall survival (OS) of 15.9 mos (80% CI, 14.1–20.3). Methods: LATIFY is a phase 3, open-label, randomized, multicenter study in pts with NSCLC (NCT05450692). Key inclusion criteria are age ≥18 years; ECOG performance status 0–1; documented EGFR and ALK wild-type, and tumor cell PD-L1 status; and adequate organ and bone marrow function. Stable brain metastases are allowed. Pts should be eligible for second- or third-line therapy, and must have received an anti-PD-(L)1 therapy and a platinum-containing doublet regimen for locally advanced or metastatic NSCLC either separately or in combination, but no other prior therapies. Key exclusion criteria include mixed small-cell lung and NSCLC histology, unresolved toxicities of Grade ≥2 (NCI CTCAE v5.0) from prior therapy, active or prior autoimmune or inflammatory disorders, &gt; 1 line of prior anti-PD-(L)1 therapy (alone or in combination), and &gt; 1 line of platinum-based CT in a metastatic setting. Pts are randomized 1:1 to receive either oral ceralasertib 240 mg twice daily on Days (D) 1–7 with IV durvalumab 1500 mg on D8 (28-day cycle) or IV docetaxel 75 mg/m2 (D1, 21-day cycle). The primary objective is to assess efficacy by OS. Secondary objectives include evaluating efficacy by PFS, objective response rate and disease control rate by RECIST v1.1; duration of, and time to, response; time to second progression or death; OS at 12 mos; time to deterioration of health-related quality of life and physical function; determining the pharmacokinetics of ceralasertib; and assessing safety. Approximately 580 pts will be recruited from around 21 countries in the Americas, Europe, and Asia Pacific. Clinical trial information: NCT05450692 .