PIK3CA Mutation Status Research Articles

Molecular alterations influencing the prognostic outcome in small pancreatic cancer (≤ 2 cm)

Abstract Purpose Pancreatic cancer (PC) is the most lethal cancer. The prognosis of small PC (tumor smaller than 20 mm) is better than that of larger PC tumors, indicating the importance of detecting early-stage PC for patient outcome. The aim of this study was to elucidate the molecular features in small PC (≤ 20 mm). Methods This study included 79 PC tumors (≤ 20 mm in pathological examination) resected between 2004 and 2022. c-Myc, Caveolin-1, Smad4, and Thrombospondin-1 were examined by immunostaining. These molecular alterations were compared in PC patients with tumor size ≤10 mm (n = 11) (14%) and 10 mm < tumor size ≤20 mm (n = 68) (86%). Mutation analyses of KRAS, PIK3CA, and BRAF were performed by pyrosequencing in 22 PCs. Results PC with 10 mm < tumor size ≤20 mm showed significantly worse overall survival and disease-free survival than PC with tumor size <10 mm (P = 0.024 and P = 0.028). Tumor c-Myc and stromal Caveolin-1 expressions were significantly increased in tumors larger than 10 mm (P = 0.02 and P = 0.04). c-Myc and Caveolin-1 expressions were associated with poor disease-free survival and overall survival. KRAS, PIK3CA, and BRAF mutation status did not differ between the two groups. Conclusions Tumor c-Myc and stromal Caveolin-1 overexpressions were detected in tumors larger than 10 mm. Their overexpressions were associated with worse prognosis even in small PC. These molecular alterations in small PC may be a clue for the detection of early-stage PC.

NCOG-35. IDENTIFYING PROGNOSTIC FACTORS IN PEDIATRIC DIFFUSE MIDLINE GLIOMAS, H3 K27-ALTERED

Abstract INTRODUCTION Diffuse midline gliomas, H3 K27-altered (DMG) are rare, grade 4 tumors localized to the diencephalon, brainstem, and cervical spine. DMGs, characterized by a K27M missense mutation in histone H3, often cannot be safely resected and predominantly present with poor outcomes in children. Few prognostic factors for DMGs have been identified and/or need to be further elucidated, including adolescent age of onset, re-irradiation status, and tumor molecular profile (i.e., PIK3CA mutation). Herein, we describe the clinical outcomes of DMG patients at our institution. METHODS Pediatric patients (<18 y/o) between 2015 and 2023 with biopsy-proven DMG were reviewed. Demographic, treatment, and tumor characteristics (histologic and molecular) were recorded. Adolescent-onset DMGs were defined as patients ≥10 y/o at diagnosis and early-onset DMGs were defined as patients <10 y/o. Progression free survival (PFS) and overall survival (OS) were calculated according to the Kaplan Meier-method. Multivariate regression analyses were performed. RESULTS Twenty-one patients were included (median age=9 y/o). Early-onset DMGs (n=13) progressed significantly earlier and experienced significantly greater mortality than adolescent-onset DMGs (n=8); PFS and OS at 12 months was 7.7% and 23% for early-onset DMGs and 50% and 87.5% for adolescent-onset DMGs (PFS: p<0.01, OS: p<0.02). Patients that received re-irradiation for progressive disease (n=9, mean=84Gy) had an OS of 75% at 12 months, which was significantly greater than an OS of 23% at 12 months (p<0.05) for patients that received no re-irradiation (n=12, mean=53Gy). PIK3CA mutation status was identified as an independent predictor of survival, with PIK3CA-mutant DMGs (n=7) having a median survival of 4.1 months versus 9.7 months for PIK3CA-WT DMGs. CONCLUSION We describe a pediatric cohort that presents several possible prognostic factors of survival in DMGs. Our findings on adolescent age of onset, if further corroborated, has the potential to inform the design and enrollment of DMG clinical trials.

Pre-operative dual-time-point [18F]FET PET differentiates CDKN2A/B loss and PIK3CA mutation status in adult-type diffuse glioma: a single-center prospective study.

While [18F]FET PET plays a complementary role in glioma imaging, it needs to be more comprehensively understood for improved characterization of glioma prior to surgery given the evolving landscape of molecular neuropathology. Thus, we investigated the utility of pre-operative dual-time-point [18F]FET PET in correlation with next-generation sequencing (NGS) data in patients with adult-type diffuse glioma (ADG). Adult patients who were suspected to have primary glioma were prospectively recruited between June 2021 and January 2024. They underwent pre-operative dual-time-point static PET/CT at 20min (early) and 80min (delay) after [18F]FET injection. Semi-quantitative parameters of the hottest lesion (SUVmax) of tumour and the hottest lesion-to-normal brain ratio (TBRmax) were assessed from each summed image. Furthermore, the percentage changes (△) of SUVmax and TBRmax between two images were calculated. Histopathology of glioma was determined according to the 2021 WHO classification and NGS data. This study investigated a dozen genes in 76 patients, of whom 51 had isocitrate dehydrogenase (IDH)-wild-type glioblastoma, 13 had IDH-mutant astrocytoma, and 12 had IDH-mutant oligodendroglioma. Every tumour was [18F]FET-avid having TBRmax more than 1.6. Patients with CDKN2A/B loss had significantly higher values of SUVmax (5.7 ± 1.6 vs. 4.7 ± 1.3, p = 0.004; 5.0 ± 1.4 vs. 4.4 ± 1.2, p = 0.026) and TBRmax (6.5 ± 1.8 vs. 5.1 ± 1.7, p = 0.001; 5.3 ± 1.5 vs. 4.3 ± 1.3, p = 0.004) in both scans than patients without CDKN2A/B loss, even after adjustment for age, MRI enhancement, tumor grade and type of pathology. Furthermore, patients with PIK3CA mutation (16.2 ± 11.8 vs. 6.7 ± 11.6, p = 0.007) had significantly higher △SUVmax than patients without PIK3CA mutation, even after adjustment for age, MRI enhancement, tumor grade, and type of pathology. Among the dozen genes investigated in this prospective study in patients with ADG, we found out that CDKN2A/B loss and PIK3CA mutation status could be differentiated by pre-operative dual-time-point [18F]FET PET/CT.

PI3K/PTEN/mTOR pathway dynamic tracking and prognostic value in HR+/HER2− BC patients with residual disease after neoadjuvant chemotherapy: a cohort study

AimsHormone receptor-positive (HR)+/HER2− breast cancer (BC) is highly heterogeneous, with PI3K/PTEN/mTOR pathway alterations emerging as possible players within this complexity. We longitudinally tracked PI3K/PTEN/mTOR pathway dynamics from baseline biopsy to...

Analysis of PIK3CA mutations in the primary and recurrent tumors of hormone receptor positive/human epidermal growth factor receptor 2 negative breast cancer.

Our aim was to compare the PIK3CA mutation status in matched primary and recurrent tumors of hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) breast cancer (BC) to gain insight into the optimization of patient selection and detection time for PIK3CA-targeted therapy. The data were from 3035 patients with BC diagnosed at the Breast Disease Center, Peking University First Hospital, between January 2008 and December 2017. Matched primary and recurrent samples were profiled using amplification-refractory mutation system-polymerase chain reaction covering 11 mutational hotspots in PIK3CA. PIK3CA mutations were detected in 54.3% primary tumors and 48.6% corresponding recurrences. PIK3CA mutation was detected in 37.5% cases in the locoregional recurrent group and 40.0% of distant metastasis, without a statistical difference. Besides, PIK3CA mutations were concordant in 88.6% of the matched pairs. For patients treated with neoadjuvant chemotherapy, 100% concordance was observed. However, PIK3CA mutation was neither correlated with clinicopathological features nor associated with clinical outcomes. Mutations in PIK3CA in HR+/HER2- BC generally progressed to recurrent tumors. The high concordance rate of PIK3CA mutation status between primary tumors and corresponding recurrences suggests that the detection of primary tumors could be a substitute approach when recurrent samples are not easily obtainable.

Aberrant p53 immunostaining patterns in breast carcinoma of no special type strongly correlate with presence and type of TP53 mutations

Recent studies have revealed an association between TP53 mutations and endocrine resistance in hormone receptor-positive, HER2-negative breast cancer (HR + HER2 −BC). Aberrant p53 immunostaining (IHC) patterns may provide a surrogate marker for TP53 mutations. Building upon a ternary algorithm of aberrant staining patterns, this study evaluates the reliability of p53 IHC as screening tool for TP53 mutations in BC (NST). Furthermore, it describes the histopathological and molecular characteristics of TP53-mutated cases, along with the mutational status of PIK3CA. This study comprised 131 early-stage, node-negative BCs with available core biopsies and resection specimens. Cases were categorized as follows: HR + HER2 − (85 cases), HER2 + (21 cases) and triple negative (TN, 25 cases). Aberrant IHC staining patterns for p53 were defined as overexpression (OE), complete absence (CA) and cytoplasmic (CY). In addition, targeted sequencing of TP53 and PIK3CA genes was performed. TP53 mutations were identified in 53 of 126 cases (42.1%). Within HR + HER2 − cases, TP53 mutations were found in 17 of 80 cases (21.3%). IHC accurately predicted TP53 mutation in 96.2% of cases with a specificity of 100%. Additionally, there was a significant agreement between missense mutations and OE, as well as between truncating mutations and CA (κ 73% and 76%). CY was observed in two TN cases with truncating mutations within the nuclear localization signalling domain of p53. TP53-mutated cases exhibited higher grade, greater nuclear pleomorphism and higher Ki-67 proliferation index and were associated with the PIK3CA wild-type status (p < 0.001). p53 IHC may provide a useful screening tool for identifying TP53-mutated BC of NST.

A Phase I Trial of Alpelisib Combined With Capecitabine in Patients With HER2-Negative Metastatic Breast Cancer

BackgroundAlpelisib is an oral α-specific class I PI3K inhibitor approved in combination with fulvestrant for the treatment of PIK3CA-mutated hormone receptor-positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer. The tolerability of this drug with the oral chemotherapy capecitabine is unknown. Patients and MethodsThis phase I trial evaluated the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of alpelisib (250 mg or 300 mg daily for 3-weeks) with capecitabine (1000 mg/m2 twice daily for 2-weeks followed by a 1-week rest period) in patients with metastatic HER2-negative breast cancer, regardless of PIK3CA mutation status. ResultsEighteen patients were treated with alpelisib-capecitabine. Half of the patients had HR+ breast cancer, and 16 had prior systemic therapy for metastatic disease. The MTD of alpelisib was 250 mg daily in combination with capecitabine 1000 mg/m2 twice daily. DLTs included hyperglycemia, QTc prolongation, fatigue, and chest pain. The most common grade 3 adverse event (AE) was hyperglycemia (28%). No grade 4 AEs were observed. Three patients discontinued therapy due to an AE. One-third of patients required dose reduction of both alpelisib and capecitabine. Four patients experienced a partial response and 8 patients experienced stable disease. The median progression-free survival was 9.7 months (95% CI 2.8-13.5 months) and median overall survival was 18.2 months (95% CI 7.2-35.2 months). Twelve patients had PIK3CA mutation testing completed, of these 2 had known or likely deleterious PIK3CA mutation. ConclusionThis study provides safety data for an oral combination therapy of alpelisib-capecitabine and defines tolerable doses for further study.

A Multiplex Assay for Fast PIK3CA Hotspot Mutation Characterization in a Single Specimen by 3-Color Digital PCR Analysis.

Activating mutations in the phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gene have been detected often in solid tumors. Targeted therapy for mutant PIK3CA is now available in the clinic, making molecular diagnostics pivotal. Our aim was to design a multiplex digital PCR (dPCR) assay to evaluate the 4 most common PIK3CA hotspot mutations simultaneously to characterize and quantify these in liquid biopsies. A multiplex assay was developed to detect exon 9 p.E542K and p.E545K mutations, and exon 20 p.H1047L and p.H1047R mutations using the Stilla 3-color dPCR Naica system. The assay was evaluated on stock and pre-amplified DNA from cell lines with the above mutations as single and pooled samples, and on cell-free DNA (cfDNA) from healthy blood donors (HBDs) and breast cancer patients, to determine detection thresholds and diagnostic accuracy. The assay distinguished all 4 PIK3CA mutations in (cf)DNA, and also when dual mutations were present. Detection thresholds of stock and pre-amplified cfDNA samples were 0.11 and 0.40 copies/uL (cp/uL) for mutant copies concentration, and 0.003% and 0.68% for variant allele frequencies (VAFs), respectively. The assay confirmed the PIK3CA (mutation) status as defined by targeted next-generation sequencing (NGS) in 82 out of 96 patients that were mutant for PIK3CA, and in 11 out of 12 patients with wild-type PIK3CA. Our designed multiplex dPCR assay detected PIK3CA mutations with high accuracy in stock and pre-amplified cfDNA. Furthermore, it is affordable and demands less cfDNA input when compared to available uniplex dPCR assays and NGS analyses.

Highly consistency of PIK3CA mutation spectrum between circulating tumor DNA and paired tissue in lung cancer patients

BackgroundPhosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations are associated with drug resistance and prognosis in lung cancer; however, the consistency and clinical value of PIK3CA mutations between tissue and liquid samples are unknown. MethodsCirculating tumor DNA (ctDNA) and matched tumor tissue samples from 405 advanced lung cancer patients were collected at Jilin Cancer Hospital between 2018 and 2022, and the PIK3CA mutation status was sequenced using next-generation sequencing based on a 520 gene panel. The viability of different mutant lung cancer cells was detected using MTT assay. ResultsPIK3CA mutations were detected in 46 (5.68 %) of 810 lung cancer samples, with 21 (5.19 %) of 405 plasma samples and 25 (6.17 %) of 405 matched tissues. p.Glu542Lys, p.Glu545Lys, and p.His1047Arg were the most common mutation types of PIK3CA in both the ctDNA and tissue samples. The concordance of PIK3CA mutations was 97.53 % between ctDNA and matched tissues (kappa: 0.770, P = 0.000), with sensitivity/true positive rate of 72.0 %, specificity/true negative rate of 99.2 %, and negative predictive value and positive predictive value of 0.982 and 0.857, respectively (AUC = 0.856, P = 0.000). Furthermore, the concordance of PIK3CA mutations was 98.26 % in lung adenocarcinoma and 96.43 % in lung squamous cell carcinoma. TP53 and EGFR were the most common concomitant mutations in ctDNA and tissues. Patients with PIK3CA mutations showed a high tumor mutational burden (TMB) (P < 0.001) and a significant correlation between bTMB and tTMB (r = 0.5986, P = 0.0041). For the tPIK3CAmut/ctDNA PIK3CAmut cohort, PI3K pathways alteration was associated with male sex (P = 0.022), old age (P = 0.007), and smoking (P = 0.001); tPIK3CAmut/ctDNA PIK3CAwt patients harbored clinicopathological factors of adenocarcinoma stage IV, with low PS score (≤1) and TMB. ConclusionThis study showed that ctDNA is highly concordant and sensitive for identifying PIK3CA mutations, suggesting that PIK3CA mutation detection in liquid samples may be an alternative clinical practice for tissues.

Improved Survival With Adjuvant Cyclooxygenase 2 Inhibition in PIK3CA-Activated Stage III Colon Cancer: CALGB/SWOG 80702 (Alliance).

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.Observational studies have associated aspirin or cyclooxygenase 2 (COX-2) inhibitor usage either before or after colorectal cancer diagnosis with lower risk of recurrence and suggest that PIK3CA mutational status is predictive of better response to COX-2 inhibition. To prospectively test whether adding the COX-2 inhibitor celecoxib to standard adjuvant chemotherapy reduces the risk of recurrence and improves survival, the National Cancer Institute sponsored the CALGB/SWOG 80702 trial (ClinicalTrials.gov identifier: NCT01150045) for patients with stage III resected colon cancer. Although the primary hypothesis for all patients did not show a statistically significant improvement in disease-free survival (DFS) with celecoxib, subgroup analysis by PIK3CA mutational status was a preplanned study. PIK3CA gain-of-function mutations were detected in 259 of 1,197 tumors with available whole-exome sequencing data. When stratified by PIK3CA status, patients with PIK3CA gain-of-function mutations treated with celecoxib exhibited improved DFS (adjusted hazard ratio [HR], 0.56 [95% CI, 0.33 to 0.96]) compared with PIK3CA wildtype patients (adjusted HR, 0.89 [95% CI, 0.70 to 1.14]), although the interaction test was nonsignificant (Pinteraction = .13). Overall survival was similarly improved for patients with PIK3CA gain-of-function mutations (adjusted HR, 0.44 [95% CI, 0.22 to 0.85]) compared with PIK3CA wildtype patients (adjusted HR, 0.94 [95% CI, 0.68 to 1.30]; Pinteraction = .04). Although the test for heterogeneity in DFS did not reach statistical significance, the results suggest potential utility of PIK3CA to consider selective usage of COX-2 inhibitors in addition to standard treatment for stage III colon cancer.

Peony exploratory analyses of biomarker changes: From baseline to surgical samples in patients with HER2+ breast cancer.

e15136 Background: PEONY (NCT02586025) is a randomized, multicenter, double-blind, placebo-controlled, phase III trial evaluating neoadjuvant and adjuvant pertuzumab/placebo with trastuzumab and docetaxel in HER2-positive early/locally advanced breast cancer. We previously reported that pertuzumab showed an improved efficacy vs. placebo in terms of total pathological complete response (tpCR), event-free survival and disease-free survival (DFS), as well as in pre-defined biomarker subgroups. Limited data are available on biomarker changes after neoadjuvant treatment in the Asian population. Thus, we aim to (1) describe the biomarker changes from baseline to surgical samples after HER2 targeted neoadjuvant therapy, and (2) explore the association of surgical biomarkers and DFS. Methods: This study will focus on biomarkers of tumor tissue samples collected at baseline and surgery among 218 non-tpCR patients, due to limited samples collected at disease progression. Samples were tested using Immunohistochemistry (IHC) for HER3, PTEN, CD8 and PD-L1. Both HER2/HER3 mRNA expression and PIK3CA mutation were assessed using a PCR based methodology. The statistical analyses were using R (4.1.3). Biomarkers were categorized as high/low either by median derived from baseline samples, or with well-established cutoffs, e.g. HER2 IHC of 3+ vs. 1/2+ and PD-L1 at 1%. The changes of biomarkers were examined among the paired samples using Fisher’s exact test and depicted by alluvial plots. Cox proportional hazard regression analysis was performed to examine the association between surgical biomarkers and DFS in pooled arms. Results: Since the surgical biomarkers are only evaluable among patients with residual disease, patients in this analysis had a higher stage, and were more likely to be node+. Of 166 paired samples, more patients show a decrease in HER2 and HER3 mRNA/IHC, PTEN IHC from baseline to surgery. PIK3CA mutation status remained the same among the majority of patients (n = 154, 95%). Immune-related biomarkers, PD-L1 and CD8, are more enriched in surgical samples compared to baseline. All these observations are similar between the two arms. No clear association has been shown in most of the biomarkers, except for PIK3CA, with DFS. Surgical tumor samples with PIK3CA mutation detected trended with a worse DFS than those with no PIK3CA mutation detected [HR: 1.81 (95% CI: 0.94 – 3.49)]. Conclusions: Of baseline and surgery paired samples, most biomarkers showed a change, except for PIK3CA mutation status. In pooled analyses, we only observed a trend of PIK3CA mutation detected in surgical samples with a worse DFS, which is in line with the association observed with baseline PIK3CA mutation status. No other associations were found between surgical biomarkers and DFS. These findings may suggest that despite biomarker changes patients continue to benefit From HER2 therapies and dual blockade. Clinical trial information: NCT02586025 .

Single-cell sequencing to elucidate the disparities in the immune microenvironment between PIK3CA mutants and wild types.

e17524 Background: In patients with cervical cancer, PIK3CA exhibits the highest mutation rate, with the predominant oncogenic alteration reported to occur in 40% of cases. Recent studies in cervical cancer have indicated that the mutation status of PIK3CA is prominently associated with a diminished overall survival. Nevertheless, in our preceding study entitled 'Efficacy and Safety of Sintilimab Plus Anlotinib for PD-L1–Positive Recurrent or Metastatic Cervical Cancer: A Multicenter, Single-Arm, Prospective Phase II Trial', the prognosis for the mutant group surpassed that of the non-mutant group. Therefore, distinguishing the differences in the immune microenvironment between PIK3CA mutant and wild-type cervical cancer patients is of great significance. Methods: We used Single-cell RNA sequencing (scRNA-seq) to analyze the tissue samples of 7 cervical cancer patients with PIK3CA mutations and 9 with wild-type. Results: We partitioned cells from both the mutated and wild-type forms of cervical cancer into nine distinct clusters. To better understand the transcriptional heterogeneity of tumor-infiltrating T lymphocytes, we re-clustered 45,574 NK/T cells into 9 clusters. A specific cell cluster, designated as CD8+ ISG15, exhibited a significant enrichment in interferon-induced genes, including ISG15, IFIT3, IFIT1, RSAD2, and IFI6. To explore intergroup differences, we performed differential analysis on the proportions of mutations and non-mutations in different subgroups. We found significant differences in CD8+ ISG15 between the mutant group and the widegroup. ISG15 plays a pivotal role in antiviral responses, and as research advances, it has been identified as a potential prognostic biomarker and therapeutic target for cancer, beyond its antiviral function. A growing body of studies indicates that ISG15 is overexpressed in the majority of tumors, however, the influence of high ISG15 expression on the overall survival of cancer patients is dependent on the cancer type. In our single-cell analysis of cervical cancer, we observed that the CD8+ ISG15 subgroup specifically expresses ISG15, and the prevalence of this subgroup is significantly greater in the PIK3CA wild-type group compared to the mutant group. Consequently, the CD8+ ISG15 subgroup is perceived as a significant subset within the cervical cancer immune microenvironment for regulating anti-tumor responses. Conclusions: We defined the CD8+ ISG15 cell cluster present in the cervical cancer immune microenvironment using scRNA-seq, and found that its proportion is significantly lower in the PIK3CA mutant group than in the wild-type group. Combined with existing research, this suggests that this subgroup plays an important role in immune regulation within the cervical cancer immune microenvironment.

Molecular profiling of serial liquid biopsy specimens utilizing cell free DNA (cfDNA) and circulating tumor cells (CTCs) in TBCRC041: A phase II study of alisertib in endocrine resistant metastatic breast cancer (MBC).

1037 Background: TBCRC041, a randomized phase 2 trial of alisertib (A) ± fulvestrant (F) in women with HR+/HER2- MBC demonstrated promising clinical activity for alisertib (1). Interrogation of baseline (PreC1) and end of cycle 1 (EOC1) cfDNA and CTCs may identify biomarkers associated with response to A±F. Methods: Plasma cfDNA was sequenced using the Guardant INFINITY platform, which includes genomic and methylated tumor fraction (mTF) analysis. Pathogenic variants were determined using publicly available databases and Mayo Clinic annotation pipelines. CTCs were identified as nucleated, EpCAM+/ cytokeratin+/ CD45- cells and assessed for ER/HER2 staining (RareCyte, Seattle). PFS was defined as the time from randomization to progression or death. EOC1-PFS differs from PFS as time starts at C2D1. Stratified log-rank tests and conditional Cox modeling were used to assess whether PFS or EOC1-PFS differed by mutations in ESR1 or PIK3CA, pre-CTC ≥ 5, or mTF&gt;1%. Results: Of the 91 eligible pts, 84 progressed, and 73 were deceased. In the 86 pts with PreC1-cfDNA results, variants were identified in ESR1 (42; 48.8%), PIK3CA (36; 41.9%), AKT1 (7; 8.1%), PTEN(7; 8.1%), BRCA1 (4; 4.7%), and BRCA2 (7; 8.1%). Pts with a PIK3CAmut had significantly decreased PFS (HR 1.8; 95%CI: 1.1 -2.9, p=0.014) but not by ESR1mut status (p=0.583). PreC1 and EOC1-mTF were determined for 78 and 76 pts, respectively. PreC1-mTF was 0-1% in 21; 1.1-10.0% in 27; and 10.1-100% in 30. mTF levels remained between 0-1% in 17 pts fell to 0-1% in 11 pts, and was 0-1% in 5 pts without a preC1-mTF determination. PFS did not differ with respect to PreC1-mTF (p=0.210), but EOC1-PFS was worse in pts with mTF &gt;1% (HR 3.0; 95%CI: 1.6 -5.2, p&lt;0.001). PreC1 and EOC1-CTC were determined for 78 and 76 pts. 36 (46.2%) pts had a PreC1 CTC count ≥ 5. EOC1-CTC levels remained at (n=17) or increased to (n=1) ≥ 5 and was ≥ 5 in 2 pts without a preC1-CTC determination. EOC1-PFS was not significantly different for EOC1-CTC ≥ 5 (p=0.065), but was significantly decreased in pts with PreC1-CTC≥5 (HR=1.8; 95%CI: 1.1-3.0; p=0.018). Broader cfDNA NGS panel and CTC-derived ER/HER2 staining results will be presented at the meeting. Conclusions: Among patients receiving A±F, PFS varied based on the PIK3CAmutation status. cfDNA and CTC assessment PreC1 and EOC1 provided complementary information. Further validation in larger datasets is needed. 1. JAMA Oncol 2023;9:815. Clinical trial information: NCT02860000 .

Association between PIK3CA mutations and disease-free survival in patients with HR+, HER2- tumors treated with adjuvant hormonal therapy: A real-world study in Croatia.

e12512 Background: Disease recurrence of early hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast tumor subtype is particularly challenging to manage due to its complex and very heterogeneous biological nature. Namely, due to primary and secondary resistance, one-quarter of patients with early disease will present with the disease recurrence. This variability in the timing of recurrence highlights the need to better identify key biomarkers that could predict therapeutic outcomes and guide personalized treatment strategies for these patients. Mutations in the phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gene have a high prevalence of 30% to 40% in HR+/HER2- advanced breast cancer. They lead to activation of the PI3K/AKT/mTOR pathway, promoting cell growth, and proliferation, and are associated with poor prognosis in advanced breast cancer. Our aim was to examine this association and impact of PIK3CA mutation status on disease free survival (DFS) in HR+/ HER2- early breast cancer patients. Methods: We conducted a multicentric, retrospective cohort study in five Croatian institutions from July 2020 to December 2021. Study included initially early HR+/HER2- breast cancer patients who have been diagnosed with disease recurrence during adjuvant hormonal treatment or within first six years of follow up. The Cobas PIK3CA Mutation Testing Kit was used for real-time PCR-based amplification and mutation detection on the Cobas z 480 analyzer. We have analyzed differences in DFS from initiation of adjuvant endocrine therapy, using Cox, proportional hazard regression. Results: There was total of 186 patients, out of which 40.9% tested positive for the PIK3CA mutation. Primary and adjuvant treatment and in particular adjuvant endocrine treatment was similar between the two groups. After adjustment for 14 relevant covariates, we found that patients with positive PIK3CA status and with H1047 PIK3CA mutation had significantly lower hazard for disease recurrence in comparison to patients with no PIK3CA mutation (HR 0.65; 95% CI 0.45; 0.95; p = 0.024; HR 6.52; 95% CI 1.15; 36.95; p = 0.034 respectively; false discovery rate, FDR &lt; 10%) and higher odds for late recurrence (p = 0.001, FDR &lt; 5%). Conclusions: This study highlights the potential impact of PIK3CA mutations on disease recurrence during/following adjuvant endocrine treatment and by that potentially opens the door for further investigation of possibly more personalized treatment strategies.

Development of a prediction model for lung metastasis by using postoperative circulating tumor DNA binding clinicopathological risk factors in patients with colorectal cancer.

e15035 Background: Lung metastasis is common in patients with colorectal cancer (CRC). However, diagnosing lung metastasis in CRC is challenging due to slow-growing pulmonary lesions. Circulating tumor DNA (ctDNA) testing provides a direct indication of the presence of minimal residual disease (MRD) which contributing to cancer recurrence. Yet, there are no reports on the potential indications of ctDNA for the site of metastasis. The objective of this study is to develop a predictive model for lung metastasis in CRC patients who have received adjuvant therapy by integrating ctDNA with clinicopathological factors. Methods: Two independent cohorts' series were evaluated including 299 patients from China as training cohort and 134 patients from Spain as validation cohort from 2012-2020. We specifically focused on the detection of ctDNA in these patients. We employed LASSO regression for optimal feature selection and built a predictive model by multivariable logistic regression. Results: In training cohort, 59/299(19.7%) patients have detectable ctDNA. In validation cohort, 24/134 (18.6%) patients have detectable ctDNA. Patients who tested ctDNA-positive had a significantly higher incidence of lung metastasis (33.9% vs. 11.2%, P&lt;0.001) compared to ctDNA-negative patients. A predictive model for lung metastasis was developed by multivariable logistic regression analysis. The model incorporated factors such as ctDNA status, preoperative carcinoembryonic antigen (CEA) level, presence of cancerous nodes, and the mutation status of Phosphatidylinositol-4,5-Bisphosphate 3-Kinase Catalytic Subunit Alpha (PIK3CA) in plasma. The lung metastasis prediction nomogram demonstrated a favorable ability to distinguish with a concordance index of 0.775 (95% CI: 0.706-0.775) during internal validation. The Hosmer-Lemeshow test, with p-value of 0.967, indicated that prediction nomogram model had a good fit. In addition, the prediction model of validation cohort demonstrated a discriminative performance with a concordance index of 0.724(95% CI: 0.698-0.724). Furthermore, the DCA (Decision Curve Analysis) and CIC (Clinical Impact Curve) in both cohorts indicated that the lung metastasis nomogram exhibited a favorable clinical net benefit. Finally, through multi-model comparison, it was found that the predictive performance of the model, which includes ctDNA and blood PIK3CA mutation status, was significantly superior to all clinical prediction models. Conclusions: A lung metastasis prediction nomogram was developed by integrating postoperative ctDNA and clinicopathological risk factors. The purpose of this nomogram is to assist clinicians in predicting the probability of lung metastasis in patients who have undergone surgery for CRC, with the aim to facilitate prompt intervention.

Association of ESR1 Germline Variants with TP53 Somatic Variants in Breast Tumors in a Genome-wide Study.

Emerging data show ancestry-specific differences in TP53 and PIK3CA mutation frequency in breast tumors suggesting that germline variants may influence somatic mutational processes. This study identified variants near ESR1 associated with TP53 mutation status and identified additional loci with suggestive association which may provide biological insight into observed differences.

Abstract PO4-13-12: PIK3CA mutational status in tissue &amp; plasma as a prognostic tool in HR+/HER2- breast cancer (BC)

Abstract Background: Activating mutations of PIK3CA gene are described in about 30-40% of BC. They confer overall worse prognosis and resistance to endocrine and chemotherapeutic therapy. Concordance between testing methods (tissue &amp; plasma) are not widely studied. We aim to correlate tissue &amp; plasma assays and to analyze the discordant cases and prognostic value of PIK3CA mutations (PIK3CAm) in HR+/HER2- BC. Methods: We performed a retrospective and unicentric analysis of PIK3CA mutational status in tissue &amp; plasma samples in patients (pts) with HR+/HER2- BC from February/21 to April/23. PIK3CA test: Cobas®PIK3CA Mutation Kit. We correlated both diagnostic methods. Kaplan-Meier and Cox models were used to analyze progression-free survival (PFS) and comparison outcomes in PIK3CAm vs wild-type (wt). Results: We analyzed 225 samples from 161pts with HR+/HER2- BC (149 in tissue &amp; 76 in plasma). PIK3CA mutations were detected in 62pts (38.5%), of which 39.6% (59pts) were detected in tissue and 11.8% (9pts) in plasma. Hotspot mutations: H1047X (45.7%), E545X (20%) and E542K (12.8%). In advanced disease, metastatic BC (mBC), tissue &amp; plasma concordance was conducted in 64 cases, with overall correlation rate of 70.3%. We found PIK3CAm in 28pts: by both methods in 9pts (32.1%) and exclusively tissue detection in 19 cases (67.8%). Plasma detection was correlated with the presence of ≥3 metastatic sites (66.7% vs 31.6%; p=0.08) and with collection of samples during disease progression (66.7% vs 47.4%; p=0.43). 80pts received treatment with CDK4/6 inhibitors + endocrine therapy. PFS was slightly shorter in PIK3CAm vs wt (24m vs 30m; HR=1.39 [95%CI,0.7-2.4], p=0.26). A sub-analysis was performed based on exons 9 &amp; 20, showing a significantly lower PFS in PIK3CAm exon 9 vs 20 population (9.7m vs 30.3m; HR=2.84 [95%CI,1.1-7.4], p=0.02). In addition, plasma detection of PIK3CAm was associated with worse PFS compared with PIK3CAm detected only in tissue (12.4m vs 29.3; HR=2.4 [95%CI,0.8-6.5], p=0.08). Although we observed a trend towards a poorer PFS in pts with visceral involvement in PIK3CAm (21.9m vs 30.1m; HR=2.82 [95%CI,0.6-12.3], p=0.14), in a multivariate analysis, mutations in exon 9 were an independent poor prognostic factor regardless visceral involvement and detection in plasma; p=0.05. Conclusions: Our results support the PIK3CA determination in tissue as the diagnostic method of choice, although further studies could better define the role of liquid biopsy in the detection of PIK3CAm. In our population, the presence of PIK3CAm confers poorer prognosis in luminal BC, being significantly worse in mutation carriers in exon 9 regardless visceral involvement and plasma mutation detection. Table. Tissue &amp; plasma correlation in patients with PIK3CA mutational status tested in our population (mBC). Citation Format: Eduardo Terán Brage, Rebeca Lozano Mejorada, Aline Rodrigues Françoso, José Antonio Muñóz Leon, Álvaro López Gutiérrez, Luis Figuero-Pérez, Daniel Morchón Araujo, María Garijo Martínez, Jonnathan Roldán Ruiz, María Mar Abad Hernández, Magdalena Sancho de Salas, Emilio Fonseca Sánchez, César Augusto Rodríguez Sánchez. PIK3CA mutational status in tissue &amp; plasma as a prognostic tool in HR+/HER2- breast cancer (BC) [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 PO4-13-12.

Abstract PS17-04: Clinical and Genomic Features of ER-Positive/HER2-negative Metastatic Breast Cancer in AURORA Molecular Screening Initiative (BIG 14-01): Mechanisms of Endocrine Therapy Resistance and Implications for Adjuvant Approaches

Abstract Background: Up to 30% of patients (pts) with ER-positive early breast cancers develop metastatic relapse. The molecular differences between endocrine therapy (ET)-sensitive and ET-resistant relapses, as well as the impact of specific adjuvant ET-based therapies, remain unclear. Methods: The AURORA program (NCT02102165) analyzed multi-omics data of paired primary (prim) and metastatic (meta) tumor tissue, along with plasma samples, from 1,156 patients with metastatic breast cancer (MBC). Targeted genome sequencing (TGS), RNA sequencing, and circulating tumor DNA analysis were performed. ET-resistance at MBC diagnosis was defined following the 5th ESO-ESMO ABC Guidelines. Results: We studied 628 pts with metastatic ER+/HER2- disease. Patient´s median age was 56 years, 133 (21%) were premenopausal, 314 (50%) had ET-resistance at recurrence (9% primary, 41% secondary), 132 (21%) had ET-sensitive recurrence, and the rest were ET-naive recurrences or de novo MBC. Adjuvant treatment was aromatase inhibitor (AI) +/- ovarian function suppression (OFS) in 288 (46%) pts, while 159 (25%) had tamoxifen only (+/- OFS). Gene expression correlation significantly differed (p &amp;lt; 0.005) based on ET-resistance in 92 paired samples. ET-sensitive (n=11) and de-novo tumors (n=41) showed higher correlation than primary (n=7) and secondary ET-resistance (n=32), regardless of adjuvant ET type. Prim and meta showed concordance in 91% of IHC subtypes and 62% of intrinsic subtypes. Intrinsic subtype showed 9% of prim luminal tumors switching to meta non-luminal, with 66% of Luminal A switching to Luminal B. Neither IHC nor intrinsic subtype switching was associated with the type of adjuvant ET or ET resistance. Pts with meta non-luminal intrinsic subtype (18%) had worse PFS on CDK4/6i (HR 4.0, 95% CI 1.9-8.7) and OS (HR 3.6, 95% CI 2.0-5.7) than luminal subtypes. TGS was performed in 534 meta (365 before 1L, 305 pairs). In meta before 1L, the dN/dS algorithm revealed selection in 17 genes, including TP53, PIK3CA, and ESR1. Mutations (mut) in ESR1, ERBB2, ERBB3, and RB1 among others, were specifically identified in meta. The incidence of ESR1mut was 3% in prim, 12.6% before 1L, 23.4% after 1L, and 4.7% in meta from ET-naive tumors (Table). Before 1L, ESR1mut was higher after adjuvant AI vs tamoxifen (21% vs. 4%, p&amp;lt; 0.001). ESR1mut incidence varied with ET-resistance (16% primary, 19% secondary, 9% sensitive, 4% ET-naïve/de novo, p&amp;lt; 0.01). Paired samples showed that ESR1mut were mainly acquired events and associated with higher ER mRNA signaling (hallmark estrogen response) compared to ESR1wt (p &amp;lt; 0.05). The agreement between ESR1mut detected in ctDNA and tissue was high before 1L (90%), and slightly lower after 1L (84%). In a multivariate model with relevant clinical factors, ESR1mut were associated with worse OS (HR 1.76, 95% CI 1.2-2.5, p=0.003), independently of TP53 and PIK3CA mutational status. Conclusion: AURORA study sheds light on metastatic tumor alterations acquired under anti-cancer therapy, in ER+/HER2- MBC. We observed a high prevalence of acquired ESR1mut prior to the initiation of first-line therapy, particularly in tumors exposed to adjuvant AI or with primary or secondary ET_resistance. The association of ESR1muts with poorer OS underscores the importance of implementing effective adjuvant ET strategies to prevent the emergence of these mutations. Frequency of driver gene mutations in primary and metastastic tumors before 1st-line treatment according to adjuvant ET and type of ET resistance Table. Citation Format: Angel Guerrero-Zotano, Matteo Benelli, Alexandre Irrthum, David Cameron, Lorenzo Ferrando, Dario Romagnoli, Marta Paoli, Arnau Llinas, Maya Dadiani, Danai Fimereli, Mafalda Oliveira, Carmela Caballero, Thayane Crestani, Elisa Agostinetto, Diogo Martins-Branco, Florentine Hilbers, Einav Gal-Yam, Marija Balic, Fatima Cardoso, Jorge Reis-Filho, Christos Sotiriou, Giuseppe Curigliano, Barbro Linderholm, Evandro de Azambuja, Susan Knox, Cristina Rotaru, Eva Ciruelos, Nancy E Davidson, Giuseppe Viale, Donatienne Taylor, Jean-Luc Canon, Lourdes Calvo, Joan Albanell, Marco Colleoni, Caroline Duhem, Nadia Harbeck, Catherine Herremans, Sibylle Loibl, Sandrine Marreaud, Elsemieke Scheepers, Alice Raimbault, Theodora Goulioti, Andrea Vingiani, Chiara Biagioni, Sebastian Vosberg, Gabriele Zoppoli, Jose Seoane, David Venet, Philippe Aftimos, Martine Piccart. Clinical and Genomic Features of ER-Positive/HER2-negative Metastatic Breast Cancer in AURORA Molecular Screening Initiative (BIG 14-01): Mechanisms of Endocrine Therapy Resistance and Implications for Adjuvant Approaches [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 PS17-04.

Abstract PO1-20-08: Primary breast implant-associated squamous cell carcinoma with subsequent TEMPUS testing and failure of immunotherapy

Abstract Primary squamous cell carcinoma of the breast is a rare entity, and there are a limited number of cases in the literature describing squamous cell carcinoma arising from breast implants. It has been hypothesized that these implant-associated cancers may arise from epithelialization of the implant capsule followed by chronic inflammation. None of the cases in the literature were treated with immunotherapy. We present a case of an aggressive, primary sarcomatoid squamous cell carcinoma of the breast arising from a breast implant that was treated unsuccessfully with simultaneous chemotherapy and immunotherapy following TEMPUS testing. Introduction: Breast augmentation is the most common plastic surgery procedure performed worldwide, with more than 300,000 done in the United States every year. While breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is extensively discussed in recent literature, other breast implant-associated cancers are rarer and less studied. Breast implant-associated squamous cell carcinoma (BIA-SCC) specifically is an extremely rare complication of breast augmentation and no guidelines for treatment exist. The American Society of Plastic Surgeons (ASPS) released a statement on BIA-SCC on 9/2022 following a safety communication from the FDA, and it is recommended health care providers submit case reports of BIA-SCC to a patient registry. Case study: We present the case of a female patient who underwent bilateral breast augmentation in 2006 with Mcghan textured, pre-pectoral, areolar saline implants. In 2022, she presented with swelling and a lump in her breast and underwent bilateral breast implant removal with capsulectomy. Pathology showed triple negative sarcomatoid squamous cell carcinoma of the right breast capsule. TEMPUS testing on the breast biopsy revealed a PIK3CA mutation and PD-L1 negative status. Her case was discussed with a multi-disciplinary team including plastic surgery, multiple oncologists, and radiation oncology and her clinical picture was determined to be most consistent with BIA-SCC. Based on the KEYNOTE-522 study, she was determined to be a candidate for neoadjuvant therapy with pembrolizumab and chemotherapy as she was newly diagnosed, previously untreated, nonmetastatic, and had a triple negative tumor. She received two cycles of carboplatin, paclitaxel, and pembrolizumab but unfortunately rapidly progressed with chest wall extension, multiple new pulmonary nodules, worsening lymphadenopathy, right ventricular tumor thrombus, and new malignant pleural effusion and was transitioned to hospice. Discussion: Seven cases of BIA-SCC, one case of squamous cell carcinoma (SCC) after liquid silicone injection augmentation, one case of squamous metaplasia on the breast implant capsule, and one case of epithelization of the breast implant capsule have been previously described in the literature (Table 1). None of the available cases of BIA-SCC report TEMPUS testing, and none of the patients were treated with immunotherapy. The origin of BIA-SCC is unclear, but several theories have been described including chronic inflammation leading to conversion of epithelial tissue on the capsule to SCC. It is unknown how the breast implant capsule might become epithelialized to begin with – introduction of epithelium intraoperatively during augmentation, rupture of epidermal cysts, existence of epithelium in the area from a childhood injury or from birth, or epithelization from chronic shear forces from the augmentation or leakage of the implant are all possibilities. With the ongoing data gathering through the FDA patient registry, we will continue to learn more about these rare cancers and potentially get further insight into their origins. Table 1 An overview of cases of BIA-SCC in the literature Citation Format: Emily Podany, Katherine Clifton. Primary breast implant-associated squamous cell carcinoma with subsequent TEMPUS testing and failure of immunotherapy [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 PO1-20-08.

Abstract PO2-20-02: A Phase 3 study of gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2- advanced breast cancer previously treated with a CDK4/6 inhibitor plus a non-steroidal aromatase inhibitor (VIKTORIA-1)

Abstract Patients who receive frontline CDK4/6 inhibitor (CDK4/6i) therapy eventually experience disease progression. Resistance to CDK4/6i is likely a transient adaptive mechanism that may be reversed by inhibition of the PI3K/mTOR pathway. Thus, combination of CDK4/6i and PI3K/mTORi after disease progression on CDK4/6i could restore sensitivity to CDK4/6i and prevent activation of the PI3K/mTOR pathway. This hypothesis was evaluated in a Phase 1b study (Layman SABCS 2021) of gedatolisib (geda), a potent inhibitor of PI3K and mTOR. Subjects with HR+/HER2- ABC treated with prior CDK4/6i received geda (180 mg IV weekly for 3 weeks, then one week off) with palbociclib (P) and fulvestrant (F). Median PFS was 12.9 months with 63% overall response rate. Efficacy was observed regardless of PIK3CA mutation status (Wesolowski SABCS 2022). Geda was well tolerated, with few discontinuations due to treatment-related adverse events (4%). The most common AE was stomatitis; hyperglycemia of any grade occurred in 26% of patients. This preliminary data, dosing schedule, and study population characteristics form the basis for the Phase 3 trial, VIKTORIA-1. This Phase 3 multinational clinical trial will evaluate geda and F with or without P in patients with HR+/HER2- ABC previously treated with any CDK4/6i in combination with a non-steroidal aromatase inhibitor (AI) therapy. Those without tumor PIK3CA mutations will be assigned to Study 1 (n=351) and randomized to Arm A (geda, P, and F), Arm B (geda and F), or Arm C (F). Those with PIK3CA mutations will be assigned to Study 2 (n=350) and randomized to Arm D (geda, P, and F), Arm E (alpelisib and F), or Arm F (geda and F). Key eligibility criteria include adults with confirmed metastatic or locally advanced breast cancer, any menopausal status, radiologically evaluable disease, and prior CDK4/6i treatment in combination with a non-steroidal AI. Prior hormonal therapy, including SERDs, is allowed. Key exclusion criteria include prior treatment with a PI3K, Akt, or mTOR inhibitor, prior treatment with chemotherapy for advanced disease, more than two lines of prior endocrine therapy, bone only disease with no soft tissue components, active CNS metastases, and type 1 diabetes or uncontrolled type 2 diabetes. The primary endpoint is PFS assessed by blinded independent central review per RECIST v1.1. Secondary endpoints included overall survival (OS), safety and tolerability, ORR, duration of response, time to response, CBR, quality of life, and pharmacokinetics. Enrollment is ongoing. This trial abstract was previously presented at the 2022 San Antonio Breast Cancer Symposium, December 6-10, 2022. Citation Format: Sara Hurvitz, Fabrice André, Massimo Cristofanilli, Giuseppe Curigliano, Antonio Giordano, Hyo Han, Miguel Martín, Barbara Pistilli, Hope Rugo, Robert Wesolowski, Igor Gorbatchevsky, Sibylle Loibl. A Phase 3 study of gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2- advanced breast cancer previously treated with a CDK4/6 inhibitor plus a non-steroidal aromatase inhibitor (VIKTORIA-1) [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 PO2-20-02.