PIK3CA Alterations Research Articles

Potential value of ctDNA monitoring in metastatic HR + /HER2 − breast cancer: longitudinal ctDNA analysis in the phase Ib MONALEESASIA trial

BackgroundThere is increasing interest in the use of liquid biopsies, but data on longitudinal analyses of circulating tumor DNA (ctDNA) remain relatively limited. Here, we report a longitudinal ctDNA analysis of MONALEESASIA, a phase Ib trial evaluating the efficacy and safety of ribociclib plus endocrine therapy (ET) in Asian patients with hormone receptor–positive, human epidermal growth factor receptor-2–negative advanced breast cancer.MethodsMONALEESASIA enrolled premenopausal and postmenopausal Japanese and postmenopausal non-Japanese Asian patients. All patients received ribociclib with ET (letrozole, fulvestrant, or tamoxifen with goserelin). ctDNA was analyzed using a targeted next-generation sequencing panel of 572 cancer-related genes and correlated by best overall response (BOR).ResultsFive hundred seventy-four cell-free DNA samples from 87 patients were tested. The most frequently altered genes at baseline included PIK3CA (29%) and TP53 (22%). Treatment with ribociclib plus ET decreased ctDNA in most patients at the first on-treatment time point, regardless of dose or ET partner. Patients with partial response and stable disease had lower ctDNA at baseline that remained low until data cutoff if no progressive disease occurred. Most patients with progressive disease as the best response had higher ctDNA at baseline that remained high at the end of treatment. For patients with partial response and stable disease with subsequent progression, ctDNA increased towards the end of treatment in most patients, with a median lead time of 83 days (14–309 days). In some patients with BOR of partial response who experienced disease progression later, specific gene alterations and total ctDNA fraction increased; this was sometimes observed concurrently with the development of new lesions without a change in target lesion size. Patients with alterations in PIK3CA and TP53 at baseline had shorter median progression-free survival compared with patients with wild-type PIK3CA and TP53, 12.7 and 7.3 months vs 19.2 and 19.4 months, respectively (P = .016 and P = .0001, respectively).ConclusionsHigher ctDNA levels and PIK3CA and TP53 alterations detected at baseline were associated with inferior outcomes. On-treatment ctDNA levels were associated with different patterns based on BOR. Longitudinal tracking of ctDNA may be useful for monitoring tumor status and detection of alterations with treatment implications.Trial registrationClinicalTrials.gov NCT02333370. Registered on January 7, 2015.

Noncanonical HPV carcinogenesis drives radiosensitization of head and neck tumors

We analyzed transcriptional data from 104 HPV+ (Human papillomavirus) HNSCC (head and neck squamous cell carcinoma) tumors together with two publicly available sources to identify highly robust transcriptional programs (modules) which could be detected consistently despite heterogeneous sequencing and quantification methodologies. Among 22 modules identified, we found a single module that naturally subclassifies HPV+ HNSCC tumors based on a bimodal pattern of gene expression, clusters all atypical features of HPV+ HNSCC biology into a single subclass, and predicts patient outcome in four independent cohorts. The subclass-defining gene set was strongly correlated with Nuclear factor kappa B (NF-κB) target expression. Tumors with high expression of this NF-κB module were rarely associated with activating PIK3CA alterations or viral integration, and also expressed higher levels of HPHPV E2 and had decreased APOBEC mutagenesis. Alternatively, they harbored inactivating alterations of key regulators of NF-κB, TNF receptor associated factor 3 (TRAF3), and cylindromatosis (CYLD), as well as retinoblastoma protein (RB1). HPV+ HNSCC cells in culture with experimental depletion of TRAF3 or CYLD displayed increased expression of the subclass-defining genes, as well as robust radio-sensitization, thus recapitulating both the tumor transcriptional state and improved treatment response observed in patient data. Across all gene sets investigated, methylation to expression correlations were the strongest for the subclass-defining, NF-κB-related genes. Increased tumor-infiltrating CD4+ T cells and increased Estrogen receptors alpha (ERα) expression were identified in NF-κB active tumors. Based on the relatively high rates of cure in HPV+ HNSCC, deintensification of therapy to reduce treatment-related morbidity is being studied at many institutions. Tumor subclassification based on oncogenic subtypes may help guide the selection of therapeutic intensity or modality for patients with HPV+ HNSCC.

Dyskerin and telomerase RNA component are sex-differentially associated with outcomes and Sunitinib response in patients with clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (ccRCC) displays sex-biased incidence, outcomes, molecular alterations and treatment efficacy; however, clinical managements are largely identical in male and female patients. Moreover, many biomarkers have been identified as predictors for ccRCC outcomes and response to therapeutic drugs, such as multitargeted tyrosine-kinase receptor (TKR) inhibitors, but little is known about their sex-specificity. Dyskerin (DKC1), encoded by the DKC1 gene within Xq28, is a telomerase co-factor stabilizing telomerase RNA component (TERC) and overexpressed in various cancers. Here, we determined whether DKC1 and/or TERC affect ccRCC sex-differentially.MethodsDKC1 and TERC expression in primary ccRCC tumors was assessed using RNA sequencing and qPCR. DKC1 association with molecular alterations and overall or progression-free survival (OS or PFS) was analyzed in the TCGA cohort of ccRCC. The IMmotion 151 and 150 ccRCC cohorts were analyzed to evaluate impacts of DKC1 and TERC on Sunitinib response and PFS.ResultsDKC1 and TERC expression was significantly upregulated in ccRCC tumors. High DKC1 expression predicts shorter PFS independently in female but not male patients. Tumors in the female DKC1-high group exhibited more frequent alterations in PIK3CA, MYC and TP53 genes. Analyses of the IMmotion 151 ccRCC cohort treated with the TKR inhibitor Sunitinib showed that female patients in the DKC1-high group was significantly associated with lower response rates (P = 0.021) accompanied by markedly shortened PFS (6.1 vs 14.2 months, P = 0.004). DKC1 and TERC expression correlated positively with each other, and higher TERC expression predicted poor Sunitinib response (P = 0.031) and shorter PFS (P = 0.004), too. However, DKC1 rather than TERC acted as an independent predictor (P < 0.001, HR = 2.0, 95% CI 1.480–2.704). In male patients, DKC1 expression was associated with neither Sunitinib response (P = 0.131) nor PFS (P = 0.184), while higher TERC levels did not predict response rates. Similar results were obtained from the analysis of the Sunitinib-treated IMmotion 150 ccRCC patients.ConclusionsDKC1 serves as an independent female-specific predictor for survival and Sunitinib efficacy in ccRCC, which contribute to better understanding of the sex-biased ccRCC pathogenesis and improve personalized interventions of ccRCC.

Targeted treatment of severe vascular malformations harboring PIK3CA and TEK mutations with alpelisib is highly effective with limited toxicity

This was a prospective cohort study of eighteen patients with large and debilitating vascular malformations with one or more major systemic complications. In all patients, we discovered activating alterations in either TEK or PIK3CA. Based on these findings, targeted treatment using the PI3K inhibitor alpelisib was started with regular check-ups, therapy duration varied from 6 to 31 months. In all patients, marked improvement in quality of life was observed. We observed radiological improvement in fourteen patients (two of them being on combination with either propranolol or sirolimus), stable disease in 2 patients. For 2 patients, an MRI scan was not available as they were shortly on treatment, however, a clinically visible response in size reduction or structure regression, together with pain relief was observed. In patients with elevated D-dimer levels before alpelisib administration, a major improvement was noted, suggesting its biomarker role. We observed overall very good tolerance of the treatment, documenting a single patient with grade 3 hyperglycemia. Patients with size reduction were offered local therapies wherever possible. Our report presents a promising approach for the treatment of VMs harboring different targetable TEK and PIK3CA gene mutations with a low toxicity profile and high efficacy.

Plasma cell-free tumor DNA, PIK3CA and TP53 mutations predicted inferior endocrine-based treatment outcome in endocrine receptor-positive metastatic breast cancer

PurposeHow to factor both tumor burden and oncogenic genomic mutations as variables to predict the outcome of endocrine-based therapy (ET) in ER-positive/HER2-negative metastatic breast cancer patients (MBC) remains to be explored.MethodBlood samples prospectively collected from 163 ER-positive/HER2-negative female MBC patients, before ET, were used for cell-free tumor DNA (cfDNA) analysis. cfDNA was subjected to next-generation sequencing (NGS) to interrogate oncogenic PIK3CA hotspot and TP53 DNA-binding domain (DBD) mutations, including single nucleotide variants (SNVs) or small insertions and deletions (InDels). The variant calling threshold was set at 0.5%. Progression-free survival (PFS) was measured from the start of the ET treatment to the time of disease progression of the same treatment regimen.ResultsOverall, the median PFS was 8.3 months (95% CI 5.7–11.1 months). The median cfDNA was 38.5 ng (range 4.4–1935 ng). The proportion of patients with PIK3CA and TP53 alterations were 25.1 and 15.3%, respectively. Patients with high total cfDNA (HR 1.74, p = 0.003), PIK3CA mutation (HR 1.74, p = 0.007), and TP53 mutation (HR 1.64, p = 0.047) in liquid biopsy conferred worse outcome after ET. Even for patients with low tumor burden, the detrimental effect of PIK3CA or TP53 mutation remained significant (p < 0.001). For patients with either PIK3CA (p < 0.001) or TP53 mutation (p = 0.004), there was significant positive correlation between allele frequency (AF) and total cfDNA.ConclusionAfter adjustment of cfDNA level, PIK3CA and TP53 mutations observed in liquid biopsy exerted detrimental effects on the outcome of ET-based regimens. The AF of PIK3CA or TP53 may be a surrogate marker for PFS.

High DNA methylation age deceleration defines an aggressive phenotype with immunoexclusion environments in endometrial carcinoma.

Like telomere shortening, global DNA hypomethylation occurs progressively with cellular divisions or in vivo aging and functions as a mitotic clock to restrain malignant transformation/progression. Several DNA-methylation (DNAm) age clocks have been established to precisely predict chronological age using normal tissues, but show DNAm age drift in tumors, which suggests disruption of this mitotic clock during carcinogenesis. Little is known about DNAm age alterations and biological/clinical implications in endometrial cancer (EC). Here we address these issues by analyzing TCGA and GSE67116 cohorts of ECs. Horvath clock analysis of these tumors unexpectedly revealed that almost 90% of them exhibited DNAm age deceleration (DNAmad) compared to patient chronological age. Combined with an additional clock named Phenoage, we identified a subset of tumors (82/429) with high DNAmad (hDNAmad+) as assessed by both clocks. Clinically, hDNAmad+ tumors were associated with advanced diseases and shorter patient survival, compared to hDNAmad- ones. Genetically, hDNAmad+ tumors were characterized by higher copy number alterations (CNAs) whereas lower tumor mutation burden. Functionally, hDNAmad+ tumors were enriched with cell cycle and DNA mismatch repair pathways. Increased PIK3CA alterations and downregulation of SCGB2A1, the inhibitor of PI3K kinase, in hDNAmad+ tumors, might promote tumor growth/proliferation and stemness. In addition, the inactivation of aging drivers/tumor suppressors (TP53, RB1, and CDKN2A) while enhanced telomere maintenance occurred more frequently in hDNAmad+ tumors, which supports sustained tumor growth. Prominently, hDNAmad+ tumors were featured with immunoexclusion microenvironments, accompanied by significantly higher levels of VTCN1 expression while lower PD-L1 and CTLA4 expression, which indicates their poor response to immune checkpoint inhibitor (ICI)-based immunotherapy. We further showed significantly higher levels of DNMT3A and 3B expression in hDNAmad+ than in hDNAmad- tumors. Thus, the tumor suppressive function of aging-like DNA hypomethylation is severely impaired in hDNAmad+ tumors, likely due to enhanced expression of DNMT3A/3B and dysregulated aging regulators. Our findings not only enrich biological knowledge of EC pathogenesis but also help improve EC risk stratification and precision ICI immunotherapy.

Mutational profiling of newly diagnosed glioblastoma to identify predictive biomarkers of efficacy and safety of anlotinib combination therapy.

e14037 Background: Glioblastoma (GBM) is highly vascular tumor with the specific pathologic feature of microvascular proliferation. Our previous phase Ⅱ clinical trial (NCT04119674) has firstly demonstrated the antiangiogenic multikinase inhibitor anlotinib combined with STUPP regimen can lengthen progression-free survival (PFS) in patients with newly diagnosed GBM. However, no biomarker for angiogenic therapy has been proved yet. Therefore, the second analysis was performed to identify the predictive biomarkers. Methods: A total of 21 patients with newly diagnosed GBM were enrolled in the retrospective research. The methylation status of the MGMT gene promoter was examined using the MDxHealth PCR assay. DNA-based whole genome sequencing was undertaken to detect the genomic alterations of patients. Results: The differences of gene aberrances between patients who reached and those who did not reach the primary endpoint were observed. ATRX and MYO15A mutations were only found in patients who had yet not experienced relapse. On contrast, the mutations of PIK3CA, HEG1, HMCN1 and RP1L1 occurred only in the recurrent group. HEG1 (HR 6.0, 95% CI 1.2-28.8, p= 0.026) and RP1L1 (HR 12.5, 95% CI 2.1-74.3, p= 0.005), genes related to angiogenesis, were both independent biomarkers of PFS. RP1L1 was also significantly associated with shorter overall survival (OS) (HR 33.4, 95% CI 3.2-351.4, p= 0.003). Interestingly, PIK3CA alterations were significantly higher in patients with cerebral than in those without ( p= 0.032, OR 16.4). Conclusions: Our study suggested that alterations in HEG1, RP1L1 and PIK3CA could be novel biomarkers for the newly diagnosed GBM patients received anti-angiogenesis combination therapy, and provided now insights for the precise treatment of GBM.

Metastatic breast cancer (MBC) with ultra-high tumor mutational burden (UHTMB): A comprehensive genomic profiling (CGP) study.

1036 Background: Pts with MBC whose tumors feature high TMB (≥ 10 mutations/Mb) are eligible for on label immune checkpoint inhibitor (ICI) treatment. This study evaluated the genomic landscape of MBC with “Ultra high” TMB, defined at &gt; 20 mutations/Mb. Methods: 2049 MBC underwent hybrid capture-based CGP to evaluate all classes of genomic alterations (GA), TMB, microsatellite instability (MSI) and trinucleotide mutational signatures. HER2 IHC results were available in a subset of pts. PD-L1 expression on immunocytes was determined by IHC (Ventana SP142). Results: 45/2049 (2.2%) of MBC were UHTMB. 45 (100%) pts had metastatic disease. 38 (84%) had documented Stage IV disease and 7 documented axillary LN metastases at the time of sequencing. Local breast tumor was used for CGP in 19 (42.2%) MBC and metastatic site biopsy was used in 26 (57.8%). When compared with 2004 non-UHTMB pts with UHTMB were older (mean 64.6 yrs vs 58.2 yrs p &lt; .0001), more often had lobular histology (40.0% vs 14.5% p &lt; .0001) and ER+ disease (86.6% vs 70.0%). Of the 35 UHTMB cases with HER2 IHC data available, 11 (31.4%%) were HER2 IHC negative (0+), 21 (60.0%) were HER2-low status (9 1+ and 12 2+/ISH negative) and 3 (8.6%) were HER2 IHC positive (3+). 1/3 HER2 IHC2+ cases and 2/45 (4.4%) of all UHTMB cases were positive for HER2 copy number gain on CGP. UHTMB cases had more driver GA/tumor (mean 9.8 vs 5.7 p &lt; .0001) and were less often TNBC (13.3% vs 27.0% p = .041) compared to non-UHTMB high cancers. Mutation signature analysis revealed APOBEC was predominant in UHTMB samples (82.5%); MMR signature was also observed in 10% of cases. MSI high status was significantly more frequent in UHTMB high cases (11.6% vs 0.4% p &lt; .0001). GA more frequently identified in UHTMB cases included CDH1 (45.5% vs 14.3% p &lt; .0001), PIK3CA (81.8% vs 37.9% p &lt; .0001), CDKN2A (11.4% vs 3.2% p = .017), ARID1A (25.0% vs 5.0% p &lt; .0001) and NF1 (20.5% vs 5.9% p = .0014). PD-L1 ( CD274) gene amplification (2.3% vs 1.3%) or protein expression by the Ventana SP142 assay (57.14% vs 51.10%) were not significantly different among groups. Conclusions: UHTMB MBC is a rare, yet clinically important subset of clinically advanced breast cancer driven by APOBEC mutagenesis, with high incidence of ER+ lobular histology and frequent alterations in CDH1 and PIK3CA. In addition to potential benefit from ICI based treatment, UHTMB MBC present with a high frequency of HER2-low status which may impact therapy decisions for this rare disease. [Table: see text]

Association of C-MYC, MYC target gene, and unfolded protein response (UPR) expression with clinical benefit from the oral aurora kinase A (AURKA) inhibitor, alisertib (A), in combination with paclitaxel (P) compared with P alone in patients (Pts) with HER2-negative metastatic breast cancer (MBC).

1037 Background: AURKA is a key regulator of the mitotic spindle, G2/M transition and epithelial-mesenchymal transition. AURKA is amplified and/or overexpressed in breast cancer and is associated with therapy resistance and worse survival. A randomized phase II trial in hormone receptor (HR)-positive, HER2-negative and triple negative (TN) MBC pts showed that addition of A to weekly P significantly improved progression-free survival (PFS) compared with P alone (O’Shaughnessy J et al. JAMA N etwork Open, 2021). Pts’ primary or metastatic disease tissues were analyzed for biomarkers associated with clinical benefit from A. Methods: Retrospective analysis of tumor whole exome and whole transcriptome sequencing of formalin-fixed paraffin embedded pre-treatment tissues from 96 pts (77 HR+, 19 TN) was performed. Clinical benefit from A+P or P was defined as having PFS of at least 6 mos and lack of benefit as PFS less than 6 mos. Enrichment for cancer gene mutations was assessed using Fisher's exact test. Transcriptome data were evaluated for differential expression with DeSeq2 and gene set enrichment analysis (GSEA) and compared to cancer hallmark gene sets. Molecular features were compared between A+P responders and non-responders, P responders and non-responders, and A+P and P responders. P-values &lt;0.05 were considered significant. Results: PIK3CA, TP53, and CDH1 were altered in 41%, 39%, and 13% of tumors, respectively, and these and other known cancer genes were not associated with A+P benefit. Alterations in AKT1, PIK3CA, ERBB2, CDH1, TP53, and KMT2C/ KMT2D, as well as amplifications of CCND1, MYB, and MDM2, did not preclude benefit from A+P. RNA expression of AURKA, or its upstream regulator, FOXM1, was not significantly different based on treatment group or benefit from A+P or P. Increased C-MYC RNA expression (p=0.008), and enrichment for MYC targets and UPR by GSEA were enriched in pts with lack of benefit from P compared to those with benefit from P (p&lt;0.05), but not in pts with lack of benefit from A+P. Wnt/Beta-catenin signaling was enriched in pts with lack of benefit from P compared to those with benefit from P (p=0.03), and with lack of benefit from A+P compared to those with benefit from A+P (p=0.086). Benefit from A+P was associated with enrichment for MYC targets and UPR compared with benefit from P (p=0.024), suggesting activity of A+P, but not P, with high MYC activation and UPR. Conclusions: A added to P improved PFS in HR+ HER2- and TN MBC pts compared with P alone. Pts whose breast cancers had increased C-MYC expression, high MYC activation and increased UPR on RNA expression derived greater clinical benefit from A+P than from P alone. Clinical trial information: NCT02187991 .

Genomics of ERBB2-Positive Breast Cancer in Young Women Before and After Exposure to Chemotherapy Plus Trastuzumab.

Erb-B2 receptor tyrosine kinase 2 (ERBB2)-positive breast cancer (BC) is particularly common in young women. Genomic features of ERBB2-positive tumors before and after chemotherapy and trastuzumab (chemo + H) have not been described in young women and are important for guiding study of therapeutic resistance in this population. From a large prospective cohort of women age 40 years or younger with BC, we identified patients with ERBB2-positive BC and tumor tissue available before and after chemo + H. Whole-exome sequencing (WES) was performed on each tumor and on germline DNA from blood. Tumor-normal pairs were analyzed for mutations and copy number (CN) changes. Twenty-two women had successful WES on samples from at least one time point; 12 of these had paired sequencing results from before and after chemo + H and 10 had successful sequencing from either time point. TP53 was the only significantly recurrently mutated gene in both pre- and post-treatment samples. MYC gene amplification was observed in four post-treatment tumors. Seven of 12 patients with paired samples showed acquired and/or clonally enriched alterations in cancer-related genes. One patient had an increased clonality putative activating mutation in ERBB2. Another patient acquired a clonal hotspot mutation in TP53. Other genomic changes acquired in post-treatment specimens included alterations in NOTCH2, STIL, PIK3CA, and GATA3. There was no significant change in median ERBB2 CN (20.3 v 22.6; Wilcoxon P = .79) between paired samples. ERBB2-positive BCs in young women displayed substantial genomic evolution after treatment with chemo + H. Approximately half of patients with paired samples demonstrated acquired and/or clonally enriched genomic changes in cancer genes. ERBB2 CN changes were uncommon. We identified several genes warranting exploration as potential mechanisms of resistance to therapy in this population.

Genomic characterization of vulvar squamous cell carcinoma to reveal differential gene expression based on clinical outcome.

e17633 Background: The greatest challenge in the management of vulvar squamous cell carcinoma (VSCC) is treatment of recurrent disease where options for surgery and radiation have been exhausted, or treatment of disease where distant metastasis is present. Identification of mutations differentially expressed between tumor from patients who died of aggressive disease and tumor from patients with an indolent course could reveal novel prognostic indicators and guide development of therapeutic drugs. Methods: From 202 consecutive patients with VSCC, patients who recurred and died of disease (group A) were identified and matched by age, tumor size, depth of invasion and nodal status with those whose disease did not recur (group B). Tumor and matched normal samples from 21 patients were assayed by a broad NGS panel covering 648 genes, including whole exome and transcriptome sequencing. Immunohistochemistry (IHC) for PD-L1 (22C3) and p16 was also performed. Results: Whole transcriptome data revealed 6 genes that were strongly differentially expressed between the aggressive and indolent groups: ACVR2A, TGM3, ROS1, NFEL2, CCND1 and BCL6. Biologically relevant DNA mutations were significantly greater in the aggressive cohort versus the indolent cohort: 7 vs 2.3 mutations per patient. The most common genomic alterations were mutations in TP53 and the promoter region of TERT. TP53 alterations occurred almost exclusively in group A. Other common genomic events include alterations of FAT1, CDKN2A, PIK3CA, CCND1, and LRP1B. All samples were MSI stable, and tumor mutational burden was similar in groups A and B. Most VSCC specimens (81%) were positive for PD-L1. Conclusions: We report that TGM3 and ACVR2A genes are significantly under-expressed in tumors with poor outcome. Further investigation into the silencing of these genes may advance knowledge of the pathogenesis of VSCC and potentially yield therapeutic targets. Clinical outcome of VSCC appears independent of MSI, TMB or PD-L1 status. [Table: see text]

Combinatorial immune biomarkers of efficacy on buparlisib and paclitaxel in patients with SCCHN: BERIL-1 sub-analysis.

e18030 Background: Previous analysis of the BERIL-1 Phase 2 clinical trial (Soulieres et al, CCR, 2018), evaluating the efficacy of Buparlisib + Paclitaxel, was one of the largest genomic landscape analyses to date in metastatic SCCHN. With the recent approval of PD-1 in this indication, we sought to expand the analysis, focusing on combinatorial biomarkers of immune infiltration in addition to specific genomic alterations. The goal is to evaluate hierarchically prognostic and predictive biomarkers to select predefined analysis in the current Phase 3 clinical trial, BURAN (NCT04338399) post immune modulatory therapy. Methods: The results of this analysis focused on combination of genomic alterations in both tumor and plasma samples. Alterations found in tumor versus plasma revealed over 50 differentially altered genes. Combination of these sample types is more comprehensive of the patients’ true mutational and copy number status; no significant differences in alteration frequency between treatment and placebo treatment arms were identified. We evaluated correlations between select biomarkers and improvement in efficacy end points of Progression Free Survival (PFS) and Overall Survival (OS) between the treatment and control arms and within the treatment arm. Results: The most frequently altered genes were, TP53 (49%), NOTCH1 (21%), PIK3CA (19%), FAT1 (15%), and CDKN2A (13%). Previous analysis demonstrated that TP53 mutations as well as high immune infiltration (&gt; 10% intratumoral or stromal TILs) showed improvement in PFS &amp; OS. Further improvement to OS was observed in subjects with high immune infiltration and TP53 (p = .031, HR = 0.52), PIK3CA (p = .005, HR = 0.34), NOTCH1(p = .046, HR = 0.13) or FAT1(p = .007; HR = 0.28) alterations when compared to non-altered subjects in the treatment arm. Further improvement to PFS was observed in subjects with high immune infiltration and TP53(p = .031, HR = 0.52) or FAT1(p = .006, HR = 0.23) alterations when compared to non-altered subjects in the treatment arm; NOTCH1 alterations showed strong trends in improved PFS. Additionally, high tumor mutational burden (TMB) combined with alterations in the TP53 pathway showed significant OS improvement (p = .052, HR = 0.44) compared with the placebo arm. Conclusions: This analysis highlights unique insights into the mechanism of Buparlisib and Paclitaxel in of metastatic SCCHN patients; a significant improvement in efficacy observed when specific alterations are considered in the context of immune infiltration. These observations will be further explored in the ongoing Phase 3 clinical trial, BURAN. Additional analysis to be presented at the meeting include prognostic and predictive value of each biomarker and combination, differences between tumor and plasma samples, and comparison with end of treatment samples.

Comprehensive molecular profiling from liquid and tissue for analysing the somatic mutational landscape in an Indian breast cancer cohort.

e13080 Background: Breast cancer is a genetically and clinically heterogeneous entity, with high prevalence in the Indian population. The primary objective of this study was to characterize the somatic mutational landscape of metastatic breast cancer in Indian patients from tumor and liquid specimens. Methods: We performed molecular profiling of 341 tumor tissue specimens and 901 blood specimens from individual breast cancer patients, with paired tissue and blood processing in a sub cohort (n=101). Targeted NGS evaluating single nucleotide alterations, copy number alterations, and fusions was performed on these specimens. Results: In the cohort with tissue-based sequencing (n = 341), TP53 was the prevalently altered gene (55%). PIK3CA and ESR1 mutations were detected in 32% and 9%, respectively. BRCA1/2 alterations were detected in 10.8%, ARID1A in 7%, KEAP1 in 6%, NF1 in 6%, and ATR in 6%. ERBB2 amplification was observed in 10% of the cases. ESR1 gene fusions were detected in 3.7%. This is clinically relevant as along with other ESR1 resistance mutations, ESR1 fusions are also known as recurrent drivers of endocrine therapy resistance and are impervious to ER-targeted therapies. In a sub cohort comprising 255 specimens, TMB analysis showed a median TMB of 5 mut/Mb (range 1 - 88 mut/Mb), and 15.3% specimens with TMB-High (≥10 mut/mb). The ctDNA analysis (n = 901) revealed TP53 being the most altered (41%) gene, followed by PIK3CA (23%), ESR1(11%), EGFR (6%) and GNAS (4%). Acquired resistance mutations in ERBB2 were identified in ctDNA analysis liquid biopsy from two patients treated with HER2-targeted therapy and were absent in corresponding tissue samples. Mutations in ESR1 were more commonly seen in liquid biopsy than paired tissue, indicating this acquired resistance alteration being better captured in ctDNA than tissue due to tumor heterogeneity and tumor evolution. This indicates causative role for ESR1 mutations in endocrine resistance but not in disease pathogenesis. Conclusions: We report the largest liquid biopsy study reporting the genomic landscape from breast cancer cases of Indian origin along with tissue based molecular landscape. High concordance of liquid for PIK3CA alteration and higher sensitivity for detection of resistance conferring alterations like ESR1 and ERBB2 shows utility of liquid biopsy profiling. It reinforces the utility of liquid biopsy as effective tool that reveal clinically relevant information including mutational status and therapeutic options and seem more relevant in acquired resistance settings. [Table: see text]

Establishment of a novel model of endometriosis-associated ovarian cancer by transplanting uterine tissue from Arid1a/Pten knockout mice

Although endometriosis is primarily benign, it has been identified as a risk factor for endometriosis-associated ovarian cancer (EAOC). Genetic alterations in ARID1A, PTEN, and PIK3CA have been reported in EAOC; however, an appropriate EAOC animal model has yet to be established. Therefore, the present study aimed to create an EAOC mouse model by transplanting uterine pieces from donor mice, in which Arid1a and/or Pten was conditionally knocked out (KO) in Pax8-expressing endometrial cells by the administration of doxycycline (DOX), onto the ovarian surface or peritoneum of recipient mice. Two weeks after transplantation, gene KO was induced by DOX and endometriotic lesions were thereafter removed. The induction of only Arid1a KO did not cause any histological changes in the endometriotic cysts of recipients. In contrast, the induction of only Pten KO evoked a stratified architecture and nuclear atypia in the epithelial lining of all endometriotic cysts, histologically corresponding to atypical endometriosis. The induction of Arid1a; Pten double-KO evoked papillary and cribriform structures with nuclear atypia in the lining of 42 and 50% of peritoneal and ovarian endometriotic cysts, respectively, which were histologically similar to EAOC. These results indicate that this mouse model is useful for investigating the mechanisms underlying the development of EAOC and the related microenvironment.

Comparative Genomic Landscape of Urothelial Carcinoma of the Bladder Among Patients of East and South Asian Genomic Ancestry.

Despite the low rate of urothelial carcinoma of the bladder (UCB) in patients of South Asian (SAS) and East Asian (EAS) descent, they make up a significant portion of the cases worldwide. Nevertheless, these patients are largely under-represented in clinical trials. We queried whether UCB arising in patients with SAS and EAS ancestry would have unique genomic features compared to the global cohort. Formalin-fixed, paraffin-embedded tissue was obtained for 8728 patients with advanced UCB. DNA was extracted and comprehensive genomic profiling was performed. Ancestry was classified using a proprietary calculation algorithm. Genomic alterations (GAs) were determined using a 324-gene hybrid-capture-based method which also calculates tumor mutational burden (TMB) and determines microsatellite status (MSI). Of the cohort, 7447 (85.3%) were EUR, 541 (6.2%) were AFR, 461 (5.3%) were of AMR, 74 (0.85%) were SAS, and 205 (2.3%) were EAS. When compared with EUR, TERT GAs were less frequent in SAS (58.1% vs. 73.6%; P = .06). When compared with non-SAS, SAS had less frequent GAs in FGFR3 (9.5% vs. 18.5%, P = .25). TERT promoter mutations were significantly less frequent in EAS compared to non-EAS (54.1% vs. 72.9%; P < .001). When compared with the non-EAS, PIK3CA alterations were significantly less common in EAS (12.7% vs. 22.1%, P = .005). The mean TMB was significantly lower in EAS vs. non-EAS (8.53 vs. 10.02; P = .05). The results from this comprehensive genomic analysis of UCB provide important insight into the possible differences in the genomic landscape in a population level. These hypothesis-generating findings require external validation and should support the inclusion of more diverse patient populations in clinical trials.

Abstract #1400018: Genetic Alterations in NRAS, TERT, PIK3CA and SPEN Genes Leading to an Aggressive Metastatic RAI Refractory Follicular Thyroid Cancer

Follicular thyroid cancer (FTC) is a well-differentiated thyroid tumor and the second most common type after papillary thyroid cancer (PTC) with higher incidence of distant metastases, more aggressive behavior, and poorer outcome than PTC Patient is 43-year-old female with 6.2 cm TR4 left thyroid nodule on Neck US. On Exam, Cricoid is deviated to the right with left thyroid firm nodule. FNA showed Follicular neoplasm. TSH level was 1.59 (0.45-4.70 mIU/L) and Free T4 level: 1.19 (0.78-2.20 ng/dl) CT scan of neck with contrast and MRI thoracic spine: Large, solid heterogenous mass in left thyroid lobe causing lateral displacement and mild narrowing of the trachea with retrosternal extension, Osteolytic lesion of T4 vertebral body and right sided pleura-based mass at the level of T7-T8 with No enlarged cervical lymph nodes. IR biopsy of vertebra: thyroid Origin Metastatic Carcinoma, Patient underwent total thyroidectomy with central neck dissection. Follicular thyroid cancer (STAGE II pT3A,pN1B,pM1) Mutational Testing: Negative BRAF and KRAS with Positive NRAS, PIK3CA, SPEN and TERT. Patient started on TSH suppression therapy. 1 month Later: Thyroglobulin: 2443.4 ng/ml (1.3-31.8), Thyroglobulin Ab< 0.9 (0.0-4.0 IU/ml), TSH 0.02 with Free T4 2.53 FDG PET: Multifocal osseous metastatic disease, predominantly in the axial skeleton Thyrogen stimulated WBS I-123 showed No evidence of residual or metastatic disease. Patient recieved 214 mCi of iodine-131. Post treatment MN scan showed accumulation of iodine in the metastatic bone lesions with small focal activity in the thyroidectomy bed. Post RAI treatment: TG trended to 1102.7 then 1307 Patient Completed 10 fractions of external beam radiation on T4 spine Ultrasound thyroid: No residual thyroid tissue or suspicious lymph nodes Oncology started Bone directed therapy with zoledronate with consideration of PIK3CA mutation targeted therapy with Everolimus or Temsirolimus FTC is more aggressive with poorer prognosis than PTC that is more likely to hematogenously disseminate, with mortality rate of 50%. The neoplastic proliferation of thyroid follicular cells develops by altering multiple molecular pathways such as the PI3K/AKT pathway involving the RAS, RAF, RET, and NTRK1 genes. RAS is a dual activator of the mitogen activated protein kinase and PI3K/AKT pathways TERT is a catalytic subunit of the telomerase complex. Reported in 11–17% of FTC. TERT promoter mutations associated with tumor aggressiveness and mortality PIK3CA encodes p110-alpha, is a catalytic subunit of phosphatidylinositol 3-kinase (PI3K) involves in thyroid cancer tumorigenesis and progression, reported in 7.7% of FTC with sensitivity to therapies targeting PI3K49-56, AKT57-58, or mTOR59-66. In our patient, pretreatment MN scan failed to show RAI avid lesions but PET showed increase FDG uptake and since receiving RAI treatment helped in lowering TG that indicate a possibility of mixture of RAI avid and non-RAI avid lesions existing at same time so RAI treatment is still recommended despite negative Diagnostic Scan for persistent elevated TG.

Abstract 6744: Cell-free DNA detection of alterations in the MAPK pathway in metastatic hormone receptor positive breast cancer: A multi-institutional analysis of incidence and clinical outcomes

Abstract Background Alterations in the MAPK pathway are known mechanisms for tumorigenesis in multiple solid tumors. While not major drivers in early breast cancers, activating MAPK pathway alterations have been invoked as potential resistance mechanisms in advanced hormone receptor positive (HR+) breast cancer. While MAPK pathway mutations are believed to be relatively rare in breast cancer, the accessibility of cell-free DNA (cfDNA) analysis allows for evaluation of their prevalence, co-occurring mutations, and associated clinical outcomes. In this study, we evaluated the incidence of MAPK pathway alterations and impact on clinical outcomes among patients with metastatic breast cancer (MBC). Methods Plasma was collected in patients with HR+ MBC at the Massachusetts General Hospital and Washington University in St. Louis, and cfDNA was analyzed via the Guardant 360 assay, a 74-gene next generation sequencing panel. The impact of MAPK pathway alterations on progression-free survival (PFS) and overall survival (OS) was analyzed using multivariable Cox regression analysis, adjusting for age, number of prior therapies, visceral metastases, de novo metastases, and PIK3CA alterations. PFS and OS were evaluated in the overall study population, as well as in subgroups that received endocrine therapy + CDK4/6 inhibitor, endocrine monotherapy and chemotherapy. Results Out of 647 HR+ MBC patients, 103 (16%) had non-synonymous mutations in the MAPK pathway detected in cfDNA. Median age was similar (61.9 and 60.7) in MAPK-altered and non-altered patients, respectively. Both groups had received a median of 2 prior lines of therapy (p=0.08). MAPK pathway alterations included NF1 (n = 45, 7.0%), KRAS (n = 22, 3.4%), BRAF (n = 22, 3.4%), MAPK1 (n = 8, 1.2%), MAP2K1 (n = 6, 0.9%), NRAS (n = 5, 0.8%), RAF1 (n = 5, 0.8%), HRAS (n = 4, 0.6%), ARAF (n = 4, 0.6%), MAP2K2 (n = 4, 0.6%), RIT1 (n = 3, 0.5%), and MAPK3 (n = 2, 0.3%). Mutant allele fractions ranged from 0.03 to 26. Co-alterations in PIK3CA occurred in 49% (n = 51), TP53 in 41% (n = 42), and ESR1 in 27% (n = 28). In multivariable analysis, patients with MAPK-altered HR+ MBC had significantly poorer median PFS, 7.6 months vs 11.5 months (HR: 1.6; p = 0.005; 95% CI: 1.2-2.2). There was no statistically significant impact on outcomes when stratifying by treatment type. Conclusions MAPK pathway alterations are associated with a significantly poorer PFS among patients with HR+ MBC. Further research is needed to independently validate these observations and evaluate the impact of genotype-directed therapy targeting MAPK-altered, HR+ MBC. Citation Format: Arielle J. Medford, Andrzej Niemierko, Whitney L. Hensing, Andrew A. Davis, Katherine Clifton, Jennifer C. Keenan, Lesli Kiedrowski, Ami N. Shah, Lorenzo Gerratana, Massimo Cristofanilli, Aditya Bardia. Cell-free DNA detection of alterations in the MAPK pathway in metastatic hormone receptor positive breast cancer: A multi-institutional analysis of incidence and clinical outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6744.

Abstract 2127: TERT C228T and KDM6A alterations are potential predictive biomarkers in non-muscle-invasive bladder cancer treated with intravesical Bacillus Calmette-Guérin instillation

Abstract Introduction: Bacillus Calmette-Guérin (BCG) is the standard of care for high-risk non-muscle-invasive bladder cancer (NMIBC) following transurethral resection. However, patients often have heterogeneous responses. Even among those who initially respond well to BCG, 10-20% relapse. Identification of reliable biomarkers predicting the efficacy of BCG remains an unmet need. En bloc resection is a novel technique representing a substantial advancement in the surgical management of NMIBC. We sought to investigate genomic and tumor microenvironmental (TME) profiles in NMIBC and explore potential predictive markers for BCG treatment following en-block resection. Methods: A total of 40 patients with high-risk NMIBC (cTis-T1N0M0) were retrospectively enrolled who underwent en bloc resection followed by BCG instillation. Surgical samples were subjected to NGS sequencing using a 520-gene panel (Burning Rock Biotech, Guangzhou) and multiplex immunofluorescence (mIF) assay. Results: The cohort had a median age of 63 years, and 80% were male. After a median follow-up of 21.8 months, 19/40 patients relapsed with a one-year relapse-free survival (RFS) rate of 57.5%. All tumors were microsatellite stable and showed a median TMB of 7.98muts/Mb. Genomic profiling revealed a high prevalence of alterations in TERT (55%), KDM6A (32.5%), KMT2D (32.5%), FGFR3(30%), PIK3CA (30%), TP53(27.5%), KMT2C (25%), and ARID1A (20%). TME analysis showed higher proportions of M1 macrophages and CD56 dim NK cells in the tumoral compartment and more intense infiltration of CD8+ T cells, exhausted CD8+T, CD56 bright NK cells, and M2 macrophages in the stromal compartment. Multivariate analysis identified TERT C228T mutation (HR=3.28 [95%CI:1.225-8.79], p=0.0181) and alteration in KDM6A (HR=2.94 [95%CI:1.040-8.29], p=0.042) as two independent factors associated with inferior RFS. Patients with concomitant TERT C228T and KDM6A alteration had the shortest RFS (median RFS:5.83months) compared with those who were free of (median RFS: NR) or harbored either one of the two alterations (median RFS:9.13months) (p=0.0022). We also found that tumoral infiltration of CD8+T cells was positively associated with RFS (HR=0.29 [95%CI:0.097-0.885], p=0.0208). Conclusion: The study comprehensively depicted the genomic and TME profiles in NMIBC and identified potential predictive biomarkers for BCG treatment. Our findings may facilitate the stratification of patients and better guide the clinical decision-making on the management of NMIBC. Citation Format: Qi-Dong Xia, Yao-Bing Chen, Jian-Xuan Sun, Chen-Qian Liu, Jin-Zhou Xu, Zhi-Peng Yao, Ye An, Meng-Yao Xu, Si-Han Zhang, Xing-Yu Zhong, Na Zeng, Si-Yang Ma, Hao-Dong He, Heng-Long Hu, Jia Hu, Yi Lu, Lin Shao, Si-Qi Li, Zheng Liu, Shao-Gang Wang. TERT C228T and KDM6A alterations are potential predictive biomarkers in non-muscle-invasive bladder cancer treated with intravesical Bacillus Calmette-Guérin instillation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2127.

Abstract 938: Outcomes of molecular tumor board recommendations for cancer patients with progression on standard of care therapies in Saudi Arabia

Abstract Introduction: Molecular Tumor Boards (MTB) are essential in Precision Oncology Programs. Gaps, however, remain in interpreting comprehensive genomic profiling (CGP) results, and determining their actionability. Our MTB, established in October 2020 and conducted at a tertiary cancer center in Saudi Arabia, focused on discussing patients with complex CGP results and recommending genomic based therapies. Meetings occurred virtually, every month, with oncologists, pathologists and genomicists attending. Methods: This is a retrospective cohort study of patients discussed in our MTB from October 2020 till October 2022. We report the outcomes of these patients who had progressive disease on standard of care (SOC) therapies, and have had non Tier 1 alterations (ESCAT classification) in their CGP reports. We chose an FDA approved, commercially available CGP, which tests 324 genes (FoundationOne CDX). We present the demographics, clinical characteristics, CGP results, recommendations of the MTB, and patient outcomes. Results: Sixty patients fitting the criteria above have been discussed. Median number of prior systemic therapy lines was 2 (range 0-8). The most common primary diagnosis was soft tissue sarcoma (25%), followed by liver and pancreato-biliary cancers (20%), followed by head and neck cancers (15%) and skin cancers (8%). Of the 60 patients, 48 patients had response evaluations. Thirty five patients (out of 48, 73%) have had recommendations for genomic based therapies based on their CGP results. Only 16 patients (out of 35, 46%) received MTB recommended therapies. Eight patients (out of 16, 50%) have remained progression free and on MTB recommended genomic therapy for 6 months and above. The commonest reasons for not receiving MTB recommended therapy were patient clinical deterioration or death (9 patients, 47%) followed by patients responding on current line of therapy (7 patients, 37%). Most common pathogenic targetable alterations were CDKN2A/B mutations (6 patients), followed by alterations in FGFR (5 patients), PTEN (4 patients), BRAF (4 patients), PIK3CA (2 patients) and ERBB2 (2 patients) followed by others (will be presented). Conclusion: Following recommendations, of the first MTB in Saudi Arabia, resulted in improved outcomes of cancer patients who had progressive disease on SOC therapies. Consideration of performing CGP and discussing patients early in their cancer journey may allow them to receive, and benefit from recommended genomic therapies earlier. Citation Format: Kanan Alshammari, Fouad Sabatin, Mehlika Hazar-Rethinam, Faizah Alotaibi, Reham Ajina, Hussam Shehata, Mohammad Alkhayyat, Abdullah Alsaleh, Mohammed Algarni. Outcomes of molecular tumor board recommendations for cancer patients with progression on standard of care therapies in Saudi Arabia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 938.

Abstract GS3-04: GS3-04 Capivasertib and fulvestrant for patients with aromatase inhibitor-resistant hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: results from the Phase III CAPItello-291 trial

Abstract Background: AKT pathway activation has been implicated in the development of endocrine therapy resistance in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2–) advanced breast cancer (ABC). In the Phase II, placebo (PBO)-controlled FAKTION trial, the addition of the pan-AKT inhibitor capivasertib to fulvestrant significantly improved progression-free survival (PFS) and overall survival in postmenopausal women with aromatase inhibitor (AI)-resistant HR+/HER2– ABC. The Phase III, randomized, double-blind, PBO-controlled CAPItello-291 trial (NCT04305496) investigated the efficacy and safety of capivasertib + fulvestrant in patients with AI-resistant HR+/HER2– ABC. Methods: Eligible pre/peri or postmenopausal women or men with HR+/HER2– ABC that had recurred or progressed on or after AI therapy with or without a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor were randomized 1:1 to receive fulvestrant (per standard dosing schedule) with either PBO or capivasertib (400 mg twice daily; 4 days on, 3 days off). Randomization was stratified by the presence of liver metastases, prior use of CDK4/6 inhibitors, and geographic location. AKT pathway alteration status (at least one qualifying PIK3CA, AKT1, or PTEN alteration) was determined using next-generation sequencing in tumor tissue. The dual primary endpoint was investigator-assessed PFS in the overall population and in patients with AKT pathway-altered tumors. Results: A total of 708 patients were randomized: 355 to capivasertib + fulvestrant and 353 to PBO + fulvestrant. Overall, 41% of patients had AKT pathway-altered tumors (48% [n=289/602] of patients with tumor sequencing results), 22% were pre/perimenopausal and 77% postmenopausal, with 1% male. Prior therapy for advanced disease included: 87% of patients with ≥1 line of prior treatment, 69% with a prior CDK4/6 inhibitor, and 18% with prior chemotherapy. Demographic and baseline characteristics were broadly balanced between the overall and altered populations and by treatment groups. At primary analysis (data cut-off Aug 15, 2022), 551 and 236 PFS events had occurred in the overall and pathway-altered populations, respectively. Overall, the median PFS was 7.2 months with capivasertib + fulvestrant and 3.6 months with PBO + fulvestrant (hazard ratio [HR] 0.60; 95% confidence interval [CI] 0.51–0.71; p&amp;lt;0.001). In patients with AKT pathway-altered tumors, median PFS was 7.3 months with capivasertib + fulvestrant and 3.1 months with PBO + fulvestrant (HR 0.50; 95% CI 0.38–0.65; p&amp;lt;0.001). The objective response rate in patients with measurable disease was 22.9% for capivasertib + fulvestrant vs 12.2% for PBO + fulvestrant overall and 28.8% vs 9.7% in the AKT pathway-altered population. The most frequent all-grade adverse events (AEs) with capivasertib + fulvestrant were diarrhea (72.4% vs 20.0% PBO + fulvestrant arm), rash (group term of rash, rash macular, rash maculo-papular, rash papular, rash pruritic; 38.0% vs 7.1%) and nausea (34.6% vs 15.4%). The most frequently reported grade ≥3 AEs were rash (group term; 12.1% vs 0.3%), diarrhea (9.3% vs 0.3%), and hyperglycemia (2.3% vs 0.3%); grade ≥3 stomatitis was 2.0% vs 0%. AEs leading to discontinuation of capivasertib/placebo were reported in 13.0% and 2.3% of patients, respectively. Conclusions: Capivasertib + fulvestrant significantly improved PFS compared to fulvestrant alone in the overall population, and in patients with AKT pathway-altered tumors, and may become a future treatment option in this setting. The safety profile of capivasertib + fulvestrant was generally manageable and consistent with prior data. Funding: CAPItello-291 is sponsored by AstraZeneca. Editorial acknowledgment: AstraZeneca-funded medical writing support was provided by Suzanne Patel, Ph.D., from BOLDSCIENCE Inc. Capivasertib was discovered by AstraZeneca subsequent to a collaboration with Astex Therapeutics (and its collaboration with the Institute of Cancer Research and Cancer Research Technology Limited). Citation Format: Nicholas Turner, Mafalda Oliveira, Sacha J. Howell, Florence Dalenc, Javier Cortés, Henry Gomez, Xichun Hu, Komal Jhaveri, Sibylle Loibl, Serafin Morales Murillo, Zbigniew Nowecki, Meena Okera, Yeon H. Park, Masakazu Toi, Lyudmila Zhukova, Chris Yan, Gaia Schiavon, Andrew Foxley, Hope Rugo. GS3-04 Capivasertib and fulvestrant for patients with aromatase inhibitor-resistant hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: results from the Phase III CAPItello-291 trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS3-04.