BRCA1 Alterations Research Articles

BIOM-31. MOLECULAR ANALYSIS OF RESECTED BREAST CANCER BRAIN METASTASES REVEALS CEREBELLAR LOCATION AND TRIPLE NEGATIVE SUBTYPE ARE NEGATIVE PROGNOSTIC FACTORS

Abstract BACKGROUND Brain metastases (BMs) are a significant cause of morbidity and mortality in metastatic breast cancer (MBC), yet prognostic and predictive biomarkers remain poorly understood. STUDY DESIGN 90 consecutive patients with breast cancer BMs who underwent surgical resection from 2006-2022 were retrospectively identified. Review of the electronic medical record and institutional cancer registry were completed to identify baseline clinical parameters and outcomes. BM mutation analysis was performed using a CLIA-certified targeted DNA mutation sequencing assay as part of routine clinical care. RESULTS All patients were female, median age at first BM resection was 57.9 years (range 27.0-81.3 years), and receptor subtypes included HR+/HER2- (n=27, 30.0%), HER2+ (n=33, 36.7%), and triple negative BC (TNBC; n=30, 33.3%). At time of first BM resection, most patients had a solitary BM (n=55, 61.1%), with anatomic locations including cerebellar (n=29, 32.2%), frontal (n=26, 28.9%), and parietal (n=17, 18.9%) sites. BM DNA mutation analysis (n= 20) revealed pathogenic alterations in TP53 (n=17, 85.0%), ERBB2 amplification (n=7, 35.0%), PIK3CA (n=4, 20.0%), BRCA1 (n=3, 15.0%), and BRCA2 (n=2, 10.0%). Most patients received postoperative radiation (n=82, 90.8%) and/or systemic therapy (n=67, 82.7%). Cerebellar location was significantly associated with the risk of developing leptomeningeal disease compared to other BM resection sites (HR = 2.75, p=0.02). Among all patients, median overall survival (OS) from first BM resection was 27.8 months (range 0.1-196.6 months). HR+/HER2- (median 37 months) or HER2+ (median 36 months) MBC was associated with significantly increased OS compared to TNBC (14.4 months) (p<0.01, log-rank test). CONCLUSIONS Patients with breast cancer BMs exhibited a median OS of >2 years following BM resection, and patients with TNBC had a significantly worse prognosis. Targetable mutations were observed in 40% of resected BM specimens, supporting the utility of molecular analysis of resected BMs to help guide clinical management.

TMPRSS2:ERG Gene Fusion Might Predict Resistance to PARP Inhibitors in Metastatic Castration-resistant Prostate Cancer.

The emergence of novel DNA damage repair (DDR) pathways in molecular-target therapy drugs (MTTD) has shown promising outcomes in treating patients with metastatic castration-resistant prostate cancer (mCRPC). About 25% of mCRPC patients have actionable deleterious aberrations in DDR genes, primarily in the homologous recombination (HR) pathway. However, the response rate in patients with BRCA1/2 or mutations in HRR-related genes is only 45%-55%, when exposed to poly ADP ribose polymerase (PARP) inhibitor-based therapy (PARPi). A frequent characteristic feature of prostate cancer (PC) is the occurrence of genomic rearrangement that affects the transmembrane protease serine 2 (TMPRSS2) and E26 transformation-specific (ETS)- transcription factor-related gene (ERG). In this study, a total of 114 patients with mCRPC had their RNA and DNA sequenced using next-generation sequencing. Based on their genetic profile of deleterious gene alterations of BRCA1/2 or ATM, six patients were selected for PARPi. Patients with TMPRSS2:ERG gene fusion and homozygous alteration in ATM or BRCA2 (n=2) or heterozygous alterations (BRCA1 or BRCA2) and lack of TMPRSS2:ERG gene fusion (n=2) did not show clinical benefit from PARPi (treatment duration <16 weeks). In contrast, patients (n=2) without TMPRSS2:ERG gene fusion and homozygous deleterious alterations in ATM or BRCA2 all had clinical benefit from PARPi (treatment duration ≥16 weeks). The TMPRSS2:ERG transcript product might be used as a PARPi resistance biomarker.

1309P A genomic scar based signature (HRDsig) and biallelic BRCA alterations identify a homologous recombination deficiency (HRD) phenotype of non-small cell lung cancer (NSCLC) potentially actionable to the PARP inhibitor rucaparib: Post-hoc analysis of lung-MAP substudy S1900A

1309P A genomic scar based signature (HRDsig) and biallelic BRCA alterations identify a homologous recombination deficiency (HRD) phenotype of non-small cell lung cancer (NSCLC) potentially actionable to the PARP inhibitor rucaparib: Post-hoc analysis of lung-MAP substudy S1900A

Hypermethylation of the BRCA2 gene promoter and its co-hypermethylation with the BRCA1 gene promoter in patients with breast cancer.

The BRCA2 gene is an important tumour suppressor in breast cancer, and alterations in BRCA2 may lead to cancer progression. The aim of the study was to investigate the association of hypermethylation of the BRCA2 gene promoter and its co-hypermethylation with the BRCA1 gene promoter with the development and course of breast cancer in women. This study included 74women with breast cancer (tumour tissue samples and peripheral blood) and 62women without oncological pathology (peripheral blood)- control group. Hypermethylation of the BRCA2 gene was significantly more frequently detected in the tumour tissue of women with breast cancer compared to their peripheral blood and peripheral blood of control subjects (p= 0.0006 and p= 0.00001, respectively). Hypermethylation of BRCA2 was more frequently detected in patients with breast cancer over the age of 50 and in patients with higher Ki67 expression levels (p= 0.045 and p= 0.045, respectively). There was a high frequency of unmethylated BRCA1 and BRCA2 gene combination in women of the control group compared to women with breast cancer, both in blood samples and tumour tissue samples (p= 0.014 and p= 0.00001, respectively). Our study confirms the hypothesis that BRCA2 hypermethylation plays an important role in the pathogenesis of breast cancer and the importance of assessing its co-hypermethylation with BRCA1 in predicting the course of the disease.

The PARP1 selective inhibitor saruparib (AZD5305) elicits potent and durable antitumor activity in patient-derived BRCA1/2-associated cancer models

BackgroundPoly (ADP-ribose) polymerase 1 and 2 (PARP1/2) inhibitors (PARPi) are targeted therapies approved for homologous recombination repair (HRR)-deficient breast, ovarian, pancreatic, and prostate cancers. Since inhibition of PARP1 is sufficient to cause synthetic lethality in tumors with homologous recombination deficiency (HRD), PARP1 selective inhibitors such as saruparib (AZD5305) are being developed. It is expected that selective PARP1 inhibition leads to a safer profile that facilitates its combination with other DNA damage repair inhibitors. Here, we aimed to characterize the antitumor activity of AZD5305 in patient-derived preclinical models compared to the first-generation PARP1/2 inhibitor olaparib and to identify mechanisms of resistance.MethodsThirteen previously characterized patient-derived tumor xenograft (PDX) models from breast, ovarian, and pancreatic cancer patients harboring germline pathogenic alterations in BRCA1, BRCA2, or PALB2 were used to evaluate the efficacy of AZD5305 alone or in combination with carboplatin or an ataxia telangiectasia and Rad3 related (ATR) inhibitor (ceralasertib) and compared it to the first-generation PARPi olaparib. We performed DNA and RNA sequencing as well as protein-based assays to identify mechanisms of acquired resistance to either PARPi.ResultsAZD5305 showed superior antitumor activity than the first-generation PARPi in terms of preclinical complete response rate (75% vs. 37%). The median preclinical progression-free survival was significantly longer in the AZD5305-treated group compared to the olaparib-treated group (> 386 days vs. 90 days). Mechanistically, AZD5305 induced more replication stress and genomic instability than the PARP1/2 inhibitor olaparib in PARPi-sensitive tumors. All tumors at progression with either PARPi (39/39) showed increase of HRR functionality by RAD51 foci formation. The most prevalent resistance mechanisms identified were the acquisition of reversion mutations in BRCA1/BRCA2 and the accumulation of hypomorphic BRCA1. AZD5305 did not sensitize PDXs with acquired resistance to olaparib but elicited profound and durable responses when combined with carboplatin or ceralasertib in 3/6 and 5/5 models, respectively.ConclusionsCollectively, these results show that the novel PARP1 selective inhibitor AZD5305 yields a potent antitumor response in PDX models with HRD and delays PARPi resistance alone or in combination with carboplatin or ceralasertib, which supports its use in the clinic as a new therapeutic option.

Olaparib Without Androgen Deprivation for High-Risk Biochemically Recurrent Prostate Cancer Following Prostatectomy

Olaparib is a poly(adenosine diphosphate-ribose) polymerase inhibitor that provides benefit in combination with hormonal therapies in patients with metastatic prostate cancer who harbor homologous recombination repair (HRR) alterations. Its efficacy in the absence of androgen deprivation therapy has not been tested. To determine the activity of olaparib monotherapy among patients with high-risk biochemically recurrent (BCR) prostate cancer after radical prostatectomy. This phase 2, single-arm nonrandomized controlled trial enrolled genetically unselected patients across 4 sites in the US from May 2017 to November 2022. Eligible patients had BCR disease following radical prostatectomy, a prostate-specific antigen (PSA) doubling time of 6 months or shorter, an absolute PSA value of 1.0 ng/mL or higher, and a testosterone level of 150 ng/dL or higher. Treatment was with olaparib, 300 mg, by mouth twice daily until doubling of the baseline PSA, clinical or radiographic progression, or unacceptable toxic effects. The primary end point was a confirmed 50% or higher decline in PSA from baseline (PSA50). Key secondary end points were outcomes by HRR alteration status, as well as safety and tolerability. Of the 51 male patients enrolled (mean [SD] age, 63.8 [6.8] years), 13 participants (26%) had a PSA50 response, all within the HRR-positive group (13 of 27 participants [48%]). All 11 participants with BRCA2 alterations experienced a PSA50 response. Common adverse events were fatigue in 32 participants (63%), nausea in 28 (55%), and leukopenia in 22 (43%), and were consistent with known adverse effects of olaparib. In this nonrandomized controlled trial, olaparib monotherapy led to high and durable PSA50 response rates in patients with BRCA2 alterations. Olaparib warrants further study as a treatment strategy for some patients with BCR prostate cancer but does not have sufficient activity in those without HRR alterations and should not be considered for those patients. ClinicalTrials.gov Identifier: NCT03047135.

Comparative analysis of the mutational landscape and evolutionary patterns of pancreatic ductal adenocarcinoma metastases in the liver or peritoneum

BackgroundPancreatic ductal adenocarcinoma (PDAC) often presents with liver or peritoneal metastases at diagnosis. Despite similar treatment approaches, patient outcomes vary between these metastatic sites. To improve targeted therapies for metastatic PDAC, a comprehensive analysis of the genetic profiles and evolutionary patterns at these distinct metastatic locations is essential. MethodsWe performed whole exome sequencing on 44 tissue samples from 27 PDAC patients, including primary tumours and matched liver or peritoneal metastases. We analysed somatic mutation profiles, signatures, and affected pathways for each group, and examined clonal evolution using subclonal architectures and phylogenetic trees. ResultsKRAS mutations remained the predominant driver alteration, with a prevalence of 89 % across all tumours. Notably, we observed site-specific differences in mutation frequencies, with KRAS alterations detected in 77.8 % (7/9) of peritoneal metastases and 87.5 % (7/8) of liver metastases. TP53 mutations exhibited a similar pattern, occurring in 55.6 % (5/9) of peritoneal and 37.5 % (3/8) of liver metastases. Intriguingly, we identified site-specific alterations in DNA repair pathway genes, including ATM and BRCA1, with distinct mutational profiles in liver versus peritoneal metastases. Furthermore, liver metastases demonstrated a significantly higher tumor mutational burden (TMB) compared to peritoneal metastases (median [IQR]: 2.14 [1.77–2.71] vs. 1.29 [1.21–1.69] mutations/Mb; P = 0.048). ConclusionsIn conclusion, metastasis of pancreatic cancer may be influenced by variables other than KRAS mutations, such as TP53. PDAC peritoneal and liver metastases may differ in potential therapeutic biomarkers. Further inquiry is needed on the biological mechanisms underlying metastasis and the treatment of diverse metastases.

Concurrent RB1 Loss and BRCA Deficiency Predicts Enhanced Immunologic Response and Long-term Survival in Tubo-ovarian High-grade Serous Carcinoma.

The purpose of this study was to evaluate RB1 expression and survival across ovarian carcinoma histotypes and how co-occurrence of BRCA1 or BRCA2 (BRCA) alterations and RB1 loss influences survival in tubo-ovarian high-grade serous carcinoma (HGSC). RB1 protein expression was classified by immunohistochemistry in ovarian carcinomas of 7,436 patients from the Ovarian Tumor Tissue Analysis consortium. We examined RB1 expression and germline BRCA status in a subset of 1,134 HGSC, and related genotype to overall survival (OS), tumor-infiltrating CD8+ lymphocytes, and transcriptomic subtypes. Using CRISPR-Cas9, we deleted RB1 in HGSC cells with and without BRCA1 alterations to model co-loss with treatment response. We performed whole-genome and transcriptome data analyses on 126 patients with primary HGSC to characterize tumors with concurrent BRCA deficiency and RB1 loss. RB1 loss was associated with longer OS in HGSC but with poorer prognosis in endometrioid ovarian carcinoma. Patients with HGSC harboring both RB1 loss and pathogenic germline BRCA variants had superior OS compared with patients with either alteration alone, and their median OS was three times longer than those without pathogenic BRCA variants and retained RB1 expression (9.3 vs. 3.1 years). Enhanced sensitivity to cisplatin and paclitaxel was seen in BRCA1-altered cells with RB1 knockout. Combined RB1 loss and BRCA deficiency correlated with transcriptional markers of enhanced IFN response, cell-cycle deregulation, and reduced epithelial-mesenchymal transition. CD8+ lymphocytes were most prevalent in BRCA-deficient HGSC with co-loss of RB1. Co-occurrence of RB1 loss and BRCA deficiency was associated with exceptionally long survival in patients with HGSC, potentially due to better treatment response and immune stimulation.

Genomic profiling and comparative analysis of male versus female metastatic breast cancer across subtypes

BackgroundMale breast cancer (MaBC) has limited data on genomic alterations. We aimed to comprehensively describe and compare MaBC’s genomics with female breast cancer’s (FBC) across subtypes.MethodsUsing genomic data from Foundation Medicine, we categorized 253 MaBC into estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative (n = 210), ER-positive/HER2-positive (n = 22) and triple-negative (n = 20). One ER-negative/HER2-positive case was excluded due to n-of-1. The genomics of the final MaBC cohort (n = 252) were compared to a FBC cohort (n = 2708) stratified by molecular subtype, with adjusted p-values. In the overall MaBC and FBC cohorts, we compared mutational prevalence in cancer susceptibility genes (CSG) (ATM/BRCA1/BRCA2/CHEK2/PALB2).ResultsComparing ER-positive/HER2-negative cases, MaBc had increased alterations in GATA3 (26.2% vs. 15.9%, p = 0.005), BRCA2 (13.8% vs. 5.3%, p < 0.001), MDM2 (13.3% vs. 6.14%, p = 0.004) and CDK4 (7.1% vs. 1.8%, p < 0.001); and decreased frequency of TP53 (11.0% vs. 42.6%, p < 0.001) and ESR1 mutations (5.7% vs. 14.6%, p < 0.001). Comparing ER-positive/HER2-positive cases, MaBC had increased short variants in ERBB2 (22.7% vs. 0.6%, p = 0.002), GATA3 (36.3% vs. 6.2%, p = 0.004), and MDM2 (36.3% vs. 4.9%, p = 0.002); decreased frequency of TP53 alterations was seen in MaBC versus FBC (9.1% vs. 61.7%, p < 0.001). Within triple-negative cases, MaBC had decreased alterations in TP53 compared to FBC (25.0% vs. 84.4%, p < 0.001). MaBC had higher frequency of CSG variants than FBC (22.6% vs. 14.6%, p < 0.05), with increased BRCA mutations in MaBC (14.6% vs. 9.1%, p < 0.05).ConclusionsAlthough MaBC and FBC share some common alterations, our study revealed several important differences relevant to tumor biology and implications for targeted therapies.

Docetaxel-oxaliplatin-capecitabine/5-fluorouracil (DOX/F) followed by docetaxel versus oxaliplatin-capecitabine/5-fluorouracil (CAPOX/FOLFOX) in HER2-negative advanced gastric cancers.

We evaluated whether the addition of docetaxel (D) to a combination comprising 5-fluorouracil/leucovorin (5-FU/LV) or capecitabine (C) plus oxaliplatin (O) (DOF/DOX) improved overall survival (OS) compared with 6 months of5-fluorouracil (5-FU) or capecitabine in combination with oxaliplatin (FOLFOX/CAPOX) alone in advanced HER2-negative gastroesophageal junction and gastric adenocarcinomas (G/GEJ). This study was an investigator-initiated, open-label, multi-institutional, randomized phase III trial in adult patients with HER2-negative advanced G/GEJs. The primary endpoint of the study was a comparison of median OS by Kaplan-Meier method. Next-generation sequencing was performed on tissue. Of the 324 patients randomly assigned between July 2020 and November 2022, 305 patients were evaluable for analysis (FOLFOX/CAPOX: 156; DOF/DOX: 149). With a median follow-up time of 19.2 months(95% Confidence Interval [CI] = 16.5 months to 21.9 months) for the entire cohort, the median OS was 10.1 months (95% CI = 9.2 to 10.9) for FOLFOX/CAPOX and 8.9 months (95% CI = 7.3 to 10.5) for DOF/DOX, and this difference was not statistically significant (P = .70). An increased proportion ofgrade 3 or grade 4 neutropenia (21% vs 3%; P < .001) and grade 2/3 neuropathy (17% vs 7%; P = .005) was seen in patients receiving DOF/DOX. Genomic profiling revealed a low incidence of microsatellite instability (1%) and a high incidence of BRCA1 (8.4%) and BRCA2 (7.5%) somatic alterations. FOLFOX or CAPOX chemotherapy for 6 months remains one of the standards of care in advanced HER2-negative gastroesophageal junction and gastric adenocarcinomas, with no additional survival benefit seen with the addition of docetaxel. Genomic profiling of patients revealed a higher than previously known incidence of somatic BRCA alterations, which requires further evaluation.CTRI (Clinical Trial Registry of India: CTRI/2020/03/023944).

Familial cancer with BRCA2 and other germline variants: A case report

High-resolution genomic studies can help understanding the predisposition to cancer by identifying constitutional genetic variants of differential penetrance and pathogenicity in a family. We present a case report of whole exome analysis in a case (62/Female) with a history of pancreatic, intestinal, and prostate cancers in the paternal side and her unaffected son from Gujarat, India. Proband showed germline alterations in BRCA2 and NOS3 genes and in NTHL1 gene in her son. BRCA2 c.8954-3C > G has conflicting interpretations being characterized as likely pathogenic and variant of unknown significance (VUS) in 2018 and 2021, while our findings in 2022 classifies it as likely pathogenic. Novel germline genetic variants NOS3 c.1246_1255del (p. Ile417Thrfster9) and NTHL1 c.374dup (p. Val127GlyfsTer43) have been classified as VUS. In-silico analysis of the BRCA2 c.8954-3C > G indicates the location of the genetic variant at the splice site. Proband and her son show co-segregation of 9 constitutional genetic variants; 8 are likely benign and one is benign according to ClinVar. Identification of germline variants and studies on functional evidence will facilitate curated genetic counselling for the family and focussed risk-reduction strategies.

Inhibition of Aberrantly Overexpressed Polo-like Kinase 4 Is a Potential Effective Treatment for DNA Damage Repair-Deficient Uterine Leiomyosarcoma.

Uterine leiomyosarcoma (LMS) is an aggressive sarcoma and a subset of which exhibits DNA repair defects. Polo-like kinase 4 (PLK4) precisely modulates mitosis, and its inhibition causes chromosome missegregation and increased DNA damage. We hypothesize that PLK4 inhibition is an effective LMS treatment. Genomic profiling of clinical uterine LMS samples was performed, and homologous recombination (HR) deficiency scores were calculated. A PLK4 inhibitor (CFI-400945) with and without an ataxia telangiectasia mutated (ATM) inhibitor (AZD0156) was tested in vitro on gynecologic sarcoma cell lines SK-UT-1, SKN, and SK-LMS-1. Findings were validated in vivo using the SK-UT-1 xenograft model in the Balb/c nude mouse model. The effects of CFI-400945 were also evaluated in a BRCA2-knockout SK-UT-1 cell line. The mechanisms of DNA repair were analyzed using a DNA damage reporter assay. Uterine LMS had a high HR deficiency score, overexpressed PLK4 mRNA, and displayed mutations in genes responsible for DNA repair. CFI-400945 demonstrated effective antitumor activity in vitro and in vivo. The addition of AZD0156 resulted in drug synergism, largely due to a preference for nonhomologous end-joining DNA repair. Compared with wild-type cells, BRCA2 knockouts were more sensitive to PLK4 inhibition when both HR and nonhomologous end-joining repairs were impaired. Uterine LMS with DNA repair defects is sensitive to PLK4 inhibition because of the effects of chromosome missegregation and increased DNA damage. Loss-of-function BRCA2 alterations or pharmacologic inhibition of ATM enhanced the efficacy of the PLK4 inhibitor. Genomic profiling of an advanced-stage or recurrent uterine LMS may guide therapy.

Acquired cystic disease associated renal cell carcinoma: A clinicopathologic and molecular study of 31 tumors

Acquired cystic disease associated renal cell carcinomas (ACD-RCC) are rare and their molecular and histopathological characteristics are still being explored. We therefore investigated the clinicopathologic and molecular characteristics of 31 tumors. The patients were predominantly male (n = 30), with tumors mainly left-sided (n = 17), unifocal (n = 19), and unilateral (n = 29) and a mean tumor size of 25 mm (range, 3–65 mm). Microscopically, several histologic patterns were present, including pure classic sieve-like (n = 4), and varied proportions of mixed classic sieve-like with papillary (n = 23), tubulocystic (n = 9), compact tubular (n = 4) and solid (n = 1) patterns. Calcium-oxalate crystals were seen in all tumors. Molecular analysis of 9 tumors using next generation sequencing showed alterations in SMARCB1 in 3 tumors (1 with frameshift deletion and 2 with copy number loss in chromosome 22 involving SMARCB1 region), however, INI1 stain was retained in all. Nonrecurrent genetic alterations in SETD2, NF1, NOTCH4, BRCA2 and CANT1 genes were also seen. Additionally, MTOR p.Pro351Ser was identified in one tumor. Copy number analysis showed gains in chromosome 16 (n = 5), 17 (n = 2) and 8 (n = 2) as well as loss in chromosome 22 (n = 2). In summary, ACD-RCC is a recognized subtype of kidney tumors, with several histological architectural patterns. Our molecular data identifies genetic alterations in chromatin modifying genes (SMARCB1 and SETD2), which may suggest a role of such genes in ACD-RCC development.

Efficacy of first line (1L) poly ADP-ribose polymerase inhibitors (PARPi) in combination with androgen pathway inhibitors (API) by homologous recombination repair (HRR) genes in metastatic castration-resistant prostate cancer (mCRPC): A living meta-analysis.

e17059 Background: It is unclear if patients with different HRR gene-mutated mCRPC derive consistent benefit from treatment with PARPi and API combination. Approval labels for PARPi+API are inconsistent across regulatory bodies in the US (Food and Drug Administration, FDA) and Europe (European Medical Agency, EMA), adding to confusion among practicing clinicians. Therefore, we aimed to assess the differential efficacy of PARP+API therapy by different genes using up-to-date trial evidence. Methods: We maintain a living meta-analysis on mCRPC treatments that is updated when new data becomes available. Here, we report data from phase III randomized control trials (RCTs) assessing PARPi+API in 1L mCRPC. The outcomes of interest included radiographic progression-free survival (rPFS) and overall survival (OS). Hazard ratios (HR) for rPFS and OS by different genes were summarized using random effects meta-analysis via inverse variance approach. Results: We have screened 27376 references since the inception of this living review. Here, we report data from three trials (15 references) with a total of 1618 patients. Frequently reported HRR gene mutations in the included trials were BRCA2 (35%), ATM (21%), CDK12 (12.2%), CHEK2 (12.2%), BRCA1 (4.6%), and PALB2 (3.4%). In terms of rPFS, statistical benefit was observed in BRCA (0.28; 95% CI: 0.13-0.59) and CDK12 (0.58; 95% CI: 0.35-0.95) subgroups, whereas no statistically significant benefit was seen in PALB2 (0.53; 95% CI: 0.21-1.32), ATM (0.93; 95% CI, 0.57-1.53), and CHEK2 (0.92; 95% CI: 0.53-1.61) subgroups. For OS, benefit was observed in BRCA (0.47; 95%CI: 0.31-0.71) subgroup. While not statistically significant, a signal of meaningful OS benefit was observed in PALB2 (0.33; 95%CI: 0.10-1.16) but no OS benefit was observed in ATM (0.97; 95% CI: 0.57-1.67), CDK12 (0.80; 95% CI: 0.36-1.78), and CHEK2 (0.81; 95% CI: 0.37-1.75) subgroups. Conclusions: Current results show that mCRPC patients with BRCA and CDK12 alterations had delayed disease progression with PARPi+API as 1L therapy. BRCA mutations are also associated with improved OS, while patients with CHEK2 and ATM derived no significant benefit with PARPi+API combination. [Table: see text]

Clinical actionability of BRCA2 alterations in uterine leiomyosarcoma: a molecular tumor board case report and a cBioPortal comprehensive analysis.

Uterine leiomyosarcoma (uLMS) represents one of the most common sarcoma histotypes, demonstrating an overall dismal prognosis. Previous studies reported uLMS to carry recurrent somatic BRCA2 homozygous deletions, related to significant clinical benefits from the use of PARP inhibitors. To investigate the prevalence in uLMS of genomic alterations (alt) in BRCA2 and other homologous recombination (HR) and DNA damage response (DDR) genes, cBioPortal was accessed and data were retrieved from studies including pan-sarcoma histologies. HR-/DDR-genes included BRCA1, BRCA2, ATM, BARD1, BRIP1, CHEK1, CHEK2, FANCA, FANCB, FANCC, FANCD2, FANCE, FANCF, FANCG, FANCI, FANCL, FANCM, NBN, PALB2, RAD51C, RAD51D, RAD50, and ATR. Only oncogenic/likely oncogenic alterations were included according to OncoKB. We reported a clinical case of a patient affected by a highly pretreated uLMS discussed at the European Institute of Oncology Molecular Tumor Board. A targeted next-generation sequencing panel demonstrated a somatic BRCA2 homozygous deletion (homDel). Upon access to Niraparib, a remarkable response of 15 months was observed before experiencing disease progression. In the genomic query, among 2393 cases, uLMS (n = 193) displayed 9 of all 31 BRCA2alt observed, representing the only sarcoma histotype showing an enrichment in BRCA2alt (4.66%; q < 0.001). All of 9 BRCA2alt were represented by homDel, which related to a high fraction of genome altered. uLMS displays a significant frequency of somatic BRCA2alt homDel. Considering their dismal prognosis, further investigation is warranted to test the use of PARPi in uLMS, and particularly in the setting of BRCA1/2 alterations.

Abstract PO3-14-11: Association between BRCA alterations detected by circulating tumor DNA and germline mutations in breast cancer patients: a retrospective mono-institutional analysis

Abstract Background: PARP inhibitors (PARPi) are a standard of care for breast cancer (BC) patients (pts) with germline BRCA (gBRCA) mutation, with benefit demonstrated also in patients with somatic (s) BRCA1/2 mutations. The use of circulating tumor (ct) DNA testing allows to detect resistant and actionable alterations in BC, but it could be associated with the incidental identification of germinal mutations. The aim of this study was to describe the incidence of both, somatic and germinal BRCA1/2 alterations, and the impact on the therapeutic outcomes in a retrospective BC cohort with clinical ctDNA testing for their BC. Materials and methods: A retrospective cohort of 245 BC pts that underwent ctDNA analysis (Guardant 360) between August 2014 and May 2023 at Weill Cornell Medical College was identified. Pts with at least a BRCA1/2 alteration, including variant of uncertain significant (VUS) and synonymous, were enrolled in the study. A descriptive analysis was performed. Results: Among 35 patients included, 34 had metastatic disease, the median age was 61 years old (IQR 40-67), and 65.7% were post-menopausal at diagnosis. 57.1% of pts had hormone receptor positive/HER2 negative (HR+/HER2-) BC, 20% had HER2 positive disease and 22.9% were triple-negative (TN) BC. Ten (28.6%) and 20 (57.1%) pts had a sBRCA1 or a sBRCA2 alteration on ctDNA, respectively; 5 pts (14.3%) had a coexisting sBRCA1/2 mutation. The median variant allele frequency (VAF) was 1.2% for BRCA1 and 2.7% for BRCA2 alterations. Furthermore, 53.3% and 6.7% of sBRCA1 and 40% and 8% of sBRCA2 mutations were identified as VUS and synonymous, respectively. The most common associated genomic alterations included TP53 (62.9%), ESR1 (20%) and PI3KCA (52%) with a median number of 4 variants (IQR 2-7). Next generation sequencing (NGS) testing on tissue was available for 3 patients: two demonstrated concordance with BRCA alterations detected by ctDNA, whereas no alteration in BRCA1/2 genes was found for the third patient despite the tissue analysis was performed at the same time of the ctDNA. Germline testing was available for 24 (69%) pts; a corresponding gBRCA1 mutation was found for 3 pts (VAF 48.6%-84.3%), and a gBRCA2 for 8 pts (VAF 26.7%-49.5%). Due to the small sample size, a univocal VAF cut-off to detect gBRCA1/2 mutations could not be calculated. Twenty-nine pts had a sBRCA1/2 mutation detected by ctDNA test before starting a new therapy; of these 55.2% had HR+/HER2- disease, while 17.2% and 27.6% were HER2 positive and TN BC, respectively. The median progression free survival (mPFS) was 10.3 (3.2-17.4) months (ms) and the 1-year and 2-year overall survival (OS) rates were 82.3% and 70.5%, respectively. The mPFS was 10.3 ms (0-25.0) for patients (n=16) that underwent chemotherapy, 5.6 ms (0-15.1) for those who had received endocrine therapy (n=9), and not reached for patients treated with PARPi (n=4). Conclusions: ctDNA analysis allows the detection of sBRCA1/2 mutations that could be missed by tissue-based testing. The identification of BRCA alterations on ctDNA could guide the use of germline testing even when these are present at a lower VAF than expected, with relevant impact on the therapeutic choices and family screening. Further evaluation to establish the impact of sBRCA1/2 detected by ctDNA on the therapeutic algorithm decision are needed. Citation Format: Letizia Pontolillo, Eleonora Nicolò, Laura Munoz Arcos, Carolina Reduzzi, Mara Serena Serafini, Amanda Kaylan Strickland, Nadia Bayou, Jeannine Donahue, Elisabetta Molteni, Lorenzo Gerratana, Diana Giannarelli, Eleni Andreopoulou, Emilio Bria, Massimo Cristofanilli. Association between BRCA alterations detected by circulating tumor DNA and germline mutations in breast cancer patients: a retrospective mono-institutional analysis [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 PO3-14-11.

Abstract PO4-05-03: Cell-free tumor DNA analysis in advanced or metastatic breast cancer patients enrolled in the German registry study PRAEGNANT

Abstract Background Accurate molecular profiling is crucial for optimal treatment decisions in advanced or metastatic breast cancer. Liquid biopsies, such as circulating cell-free tumor DNA (cfDNA, cftDNA or ctDNA), provide a non-invasive approach to monitor molecular alterations in the tumor. The German PRAEGNANT registry study aims to investigate such molecular biomarkers for precision medicine and their practical integration into clinical practice. In this context, cftDNA testing was performed as part of a PRAEGNANT research subproject, with the objectives of understanding the physician's rationale for initiating cftDNA testing, identifying detected alterations, and assessing the clinical impact of the associated findings Methods Patients with advanced or metastatic breast cancer were prospectively enrolled in the PRAEGNANT registry study (NCT02338167). The decision to undergo cftDNA testing was based on the physician's discretion. Blood samples were collected using Streck cfDNA BCT tubes and sent to the GUARDANT Health central laboratory for cftDNA extraction and subsequent next-generation sequencing analysis, employing the FDA-approved GUARDANT360 CDx test, a 74 gene panel including all guideline-recommended biomarkers, including single nucleotide variants (SNVs), indels, fusions and amplifications. Recruitment of patients occurred at four PRAEGNANT study centers between April 2022 and July 2023. The GUARDANT360 CDx report, along with a questionnaire regarding the testing intent and clinical impact of the results, was provided to the treating physician. Results 46 patients were eligible for analysis as per clinical characteristics. CftDNA analysis was successfully performed for all 46 cases. 38 (83%) harbored at least one somatic alteration in the analyzed genes. Fifteen patients (33%) harbored alterations in TP53, thirteen (28%) in PIK3CA. Five patients (11%) harbored mutations in ESR1. Somatic mutations in BRCA1 or BRCA2 were detected for five (11%) and six (13%) patients, respectively. One BRCA2 mutation was categorized as synonymous and one BRCA2 and three BRCA1 alterations as variants of uncertain significance. Eight patients (17%) harbored mutations in ATM. Most patients included were HR+HER2- (N=27, 58%). In this subgroup, eight (30%) patients had a PIK3CA alteration, five (19%) with an indication for treatment with alpelisib, eight (30%) a mutation in ATM, BRCA1 or BRCA2 and four (15%) in ESR1. Questionnaires regarding intention of testing and clinical impact were completed by 43 treating physicians (93%). Among them, 33% of patients had current indications for PARP inhibitor treatment, and 61% would consider it at the next change of therapy if a BRCA1 or BRCA2 mutation was detected. Additionally, 21% of patients had a current indication for alpelisib treatment if a relevant PIK3CA mutation was found, and 58% would consider it in the next line of treatment. Overall, cfDNA testing influenced the current or future treatment decisions in 35% of patients. Discussion The high prevalence of somatic alterations in TP53, PIK3CA, ESR1, and BRCA1/2 genes, identified through cftDNA testing with GUARDANT360 CDx, highlights their potential as biomarkers for targeted therapies in advanced/metastatic breast cancer. Detection of specific mutations influenced treatment decisions, such as eligibility for alpelisib or PARP inhibitors and might further facilitate treatment with elacestrant in future treatment lines after its approval in Germany. These findings demonstrate the clinical impact of cftDNA testing in guiding personalized treatment selection. Additionally, the identification of such somatic alterations within a registry study like PRAEGNANT presents a unique opportunity to consider enrolling these patients into biomarker-guided clinical trials. Citation Format: Hanna Hübner, Pauline Wimberger, Elena Laakmann, Eugen Ruckhäberle, Matthias Ruebner, Theresa Link, Erik Belleville, Iris Faull, Marcus Hausch, Diethelm Wallwiener, Andreas Schneeweiss, Hans Tesch, Sara Brucker, Peter A. Fasching, Volkmar Müller, Tanja Fehm. Cell-free tumor DNA analysis in advanced or metastatic breast cancer patients enrolled in the German registry study PRAEGNANT [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 PO4-05-03.

Abstract PO4-15-08: Comprehensive genomic profiling of HER2-low advanced breast cancers

Abstract Background: With the recent approval of the HER2-targeted antibody-drug conjugate (ADC) trastuzumab deruxtecan (T-Dxd) for the treatment of HER2-low advanced breast cancers (aBC), [defined as HER2 immunohistochemistry (IHC) 1+, or 2+ with negative in-situ hybridization (ISH)], there is interest to understand whether this population represents a distinct molecular entity and if there are additional biomarkers that can improve patient selection for these therapies. Here, we examined 2086 aBC cases profiled with comprehensive genomic profiling (CGP) stratified by HER2 status (negative, low, and positive) and hormone receptor (HR) status (positive and negative). Methods: Hybrid-capture CGP targeting 324 genes was performed on advanced BC samples (FoundationOne®CDx). HER2 IHC status was abstracted from pathology reports while HER2 amplification status was abstracted from CGP. Results: We examined 2086 samples of aBC patients distributed as HER2-negative (n=657; IHC 0), HER2-low (n=1012, IHC 1+, 2+ ISH non-amplified), and HER2-positive (n=417; HER2 IHC 3+). HER2-low patients were significantly older than HER2-negative patients (median 60 v 57 years, p=0.0006). HER2-low cases were more common in HR-positive than in HR-negative disease (67% vs 46%, respectively). Overall, characteristics were generally similar for genetic ancestry and TMB-H frequency across all HER2-statuses. MSI-H was rare across all HER2-statuses groups. HER2-low cases were more likely to have alterations in GATA3 (12.6% v 6.5%), ESR1 (12.4% v 7.8%), FGFR2 (4.0% v 1.8%), AR (1.1% v 0.2%), and CDH1 (15.3% v 11.6%) and less likely to harbor alterations in TP53 (44.0% v 62.4%), RB1 (6.8% v 12%), NF1 (5.5% v 9.3%), and BRCA1 (3.0% v 5.2%) when compared to HER2-negative. Some genes showed a consistent pattern of decreased frequency as HER2-IHC expression decreased from HER2-positive to HER2-low and to HER2-negative (e.g. AR alterations seen in 2.6%, 1.1% and 0.2%, respectively) while others had a increasing frequency pattern (e.g. RB1 alterations observed in 2.4%, 6.8% and 12.0%; BRCA1 seen in 1.7%, 3% and 5.2%, respectively). However, some genomic characteristics were unique to the HER2-low population (e.g. TP53 seen in 69.5% of HER2-positive and 62.4% of HER2-negative, but at a lower frequency of 44% in HER2-low cases) [Table 1]. Within the HR-positive subgroup, a lower frequency of NF1 (4.4% v 10.4%), TP53 (30.6% v 41.1%), and RB1 (4.4% v 8.0%) and a higher frequency of AR (1.0% v 0.0%) and GATA3 (16.2% v 10.9%) were observed in HER2-low vs HER2-negative cases, while within the HR-negative subgroup there was a higher frequency of GATA3 (1.2% v 0.7%) and AR (1.2% v 0.4%) and trending lower frequency of TP53 (85.7% v 90.8%) and RB1 (14.3% v 17.4%) in the HER2-low vs. HER2-negative cases. Mutations in homologous recombination repair genes (BRCA1, BRCA2, PALB2) were less frequent in HER2-low cases vs. HER2-negative cases overall (8.4% v 10.7%) and in the HR-positive (3.6% v 5.6%) and HR-negative subgroups (10.6% v 17.4%). Consistent with this, the rate of scar-based HRD signature (HRDsig) was lower in the HER2-low vs. HER2-negative subgroup (15.9% v 20.4%, p=0.02). Conclusions: These data suggest the HER2-low aBC has distinct genomic alterations before and after stratification by HR-status when compared to HER2-negative and HER2-positive aBC cases. Higher prevalence of some potentially actionable alterations in HER2-low cases, including FGFR2, AR, and ESR1, may aid in patient selection and drug development considering new combination approaches. Table 1 Summary of comprehensive genomic profiling alterations observed in HER2-low aBC compared to HER2-positive and HER2-negative cases Citation Format: Adriana Kahn, Ethan Sokol, Jeffrey Ross, Maureen Pelletier, Neal Fischbach, Lajos Pusztai, Maryam Lustberg. Comprehensive genomic profiling of HER2-low advanced breast cancers [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 PO4-15-08.

AB024. SOH24AB_017. Evaluating the oncological safety of hormone replacement therapy in BRCA alteration carriers who have undergone a bilateral oophorectomy: a systematic review and meta-analysis

AB024. SOH24AB_017. Evaluating the oncological safety of hormone replacement therapy in BRCA alteration carriers who have undergone a bilateral oophorectomy: a systematic review and meta-analysis

Abstract LB215: Polymerase θ (POLθ) inhibitors (novobiocin, ART-558, RP6685) were tested with 22 approved and investigational agents in multi-cell type spheroids of genetically selected patient-derived human tumor cell lines

Abstract The potential of novobiocin to augment cancer chemotherapy was explored in the late 1980s and early 1990s in tumor cells and tumor-bearing mice and in Phase 1 clinical trials with cyclophosphamide or cisplatin. The molecular target of novobiocin was identified to be DNA POLθ which has a role in repair of DNA double strand breaks (DSB) during mitosis. Genetic alterations which may increase or decrease POLθ inhibitor effects have been elucidated. Thirty patient-derived tumor cell lines with known BRCA, ATM, ATR, POLQ, XRCC1, PALB2, PARP1, and LIG3 alterations were screened in a complex spheroid assay (tumor cells, endothelial cells, mesenchymal stem cells) with a POLθ inhibitor (novobiocin, ART-558, or RP6685), alone or in simultaneous combination with a FDA approved or investigational anticancer small molecule, using a 7-day exposure and a CellTiter-Glo 3D luminescence endpoint. As single agents, the POLθ inhibitors had little or no cytotoxicity. Potentiation of the topoisomerase II inhibitors doxorubicin (DOX) and etoposide by the POLθ inhibitors ART-558 or RP6685 was observed in spheroids grown from the serous endometrial adenocarcinoma 922993-354-T-J3, which has ATM and BRCA2 variants. The 379773-124-R-J2 endometrioid endometrial adenocarcinoma which harbors mutant POLθ demonstrated antagonism with ART-558 in combination with PARP inhibitors and less than additive to additive cytotoxicity in combination with DOX. Activity of the Chk1/2 inhibitor prexasertib was potentiated by either ART-558 or RP6685 in the 922993-354-T-J3 complex spheroids. The combination of POLθ inhibitor ART-558 and the Chk1/2 inhibitor prexasertib produced up to 1 log increase in cytotoxicity in the 922993-354-T-J3 complex spheroids. KRAS G12D inhibitor MRTX-133 cytotoxicity against 186277-243-T-J2 colon adenocarcinoma with the KRAS G12D variant was potentiated by either ART-558 or RP6685. Potential combinations to advance into in vivo studies will be presented. This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261201500003I. Citation Format: Beverly A. Teicher, Thomas S. Dexheimer, Thomas Silvers, Nathan P. Coussens, J Paul Eder, James H. Doroshow. Polymerase θ (POLθ) inhibitors (novobiocin, ART-558, RP6685) were tested with 22 approved and investigational agents in multi-cell type spheroids of genetically selected patient-derived human tumor cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB215.