NRG-GY012: Randomized phase 2 study comparing olaparib, cediranib, and the combination of cediranib/olaparib in women with recurrent, persistent, or metastatic endometrial cancer

PURPOSE

This paper reports the efficacy of the poly (ADP-ribose) polymerase inhibitor olaparib alone and in combination with the antiangiogenesis agent cediranib compared with cediranib alone in patients with advanced endometrial cancer.

METHODS

This was open-label, randomized, phase 2 trial (NCT03660826). Eligible patients had recurrent endometrial cancer, received at least one (<3) prior lines of chemotherapy, and were Eastern Cooperative Oncology Group performance status 0 to 2. Patients were randomly assigned (1:1:1), stratified by histology (serous vs. other) to receive cediranib alone (reference arm), olaparib, or olaparib and cediranib for 28-day cycles until progression or unacceptable toxicity. The primary end point was progression-free survival in the intention-to-treat population. Homologous repair deficiency was explored using the BROCA-GO sequencing panel.

RESULTS

A total of 120 patients were enrolled and all were included in the intention-to-treat analysis. Median age was 66 (range, 41-86) years and 47 (39.2%) had serous histology. Median progression-free survival for cediranib was 3.8 months compared with 2.0 months for olaparib (hazard ratio, 1.45 [95% CI, 0.91-2.3] p = .935) and 5.5 months for olaparib/cediranib (hazard ratio, 0.7 [95% CI, 0.43-1.14] p = .064). Four patients receiving the combination had a durable response lasting more than 20 months. The most common grade 3/4 toxicities were hypertension in the cediranib (36%) and olaparib/cediranib (33%) arms, fatigue (20.5% olaparib/cediranib), and diarrhea (17.9% cediranib). The BROCA-GO panel results were not associated with response.

CONCLUSION

The combination of cediranib and olaparib demonstrated modest clinical efficacy; however, the primary end point of the study was not met. The combination was safe without unexpected toxicity.

Identification of fallopian tube microbiota and its association with ovarian cancer

Investigating the human fallopian tube (FT) microbiota has significant implications for understanding the pathogenesis of ovarian cancer (OC). In this large prospective study, we collected swabs intraoperatively from the FT and other surgical sites as controls to profile the microbiota in the FT and to assess its relationship with OC. Eighty-one OC and 106 non-cancer patients were enrolled and 1001 swabs were processed for 16S rRNA gene PCR and sequencing. We identified 84 bacterial species that may represent the FT microbiota and found a clear shift in the microbiota of the OC patients when compared to the non-cancer patients. Of the top 20 species that were most prevalent in the FT of OC patients, 60% were bacteria that predominantly reside in the gastrointestinal tract, while 30% normally reside in the mouth. Serous carcinoma had higher prevalence of almost all 84 FT bacterial species compared to the other OC subtypes. The clear shift in the FT microbiota in OC patients establishes the scientific foundation for future investigation into the role of these bacteria in the pathogenesis of OC.

Identification of fallopian tube microbiota and its association with ovarian cancer: a prospective study of intraoperative swab collections from 187 patients

Investigating the human fallopian tube (FT) microbiota has significant implications for understanding the pathogenesis of ovarian cancer (OC). In this large prospective study, we collected swabs intraoperatively from the FT and other surgical sites as controls to profile the microbiota in the FT and to assess its relationship with OC. 81 OC and 106 non-cancer patients were enrolled and 1001 swabs were processed for 16S rRNA gene PCR and sequencing. We identified 84 bacterial species that may represent the FT microbiota and found a clear shift in the microbiota of the OC patients when compared to the non-cancer patients. Of the top 20 species that were most prevalent in the FT of OC patients, 60% were bacteria that predominantly reside in the gastrointestinal tract, while 30% normally reside in the mouth. Serous carcinoma had higher prevalence of almost all 84 FT bacterial species compared to the other OC subtypes. The clear shift in the FT microbiota in OC patients establishes the scientific foundation for future investigation into the role of these bacteria in the pathogenesis of ovarian cancer. .

Adoption of Universal Testing in Endometrial Cancers for Microsatellite Instability Using Next-Generation Sequencing

PURPOSE

To assess implementation of a next-generation sequencing (NGS) assay to detect microsatellite instability (MSI) as a screen for Lynch syndrome (LS) in endometrial cancer (EC), while determining and comparing characteristics of the four molecular subtypes.

METHODS

A retrospective review was performed of 408 total patients with newly diagnosed EC: 140 patients who underwent universal screening with NGS and 268 patients who underwent screening via mismatch repair immunohistochemistry (MMR IHC) as part of a historical screening paradigm. In the NGS cohort, incidental POLE and TP53 mutations along with MSI were identified and used to characterize EC into molecular subtypes: POLE-ultramutated, MSI high (MSI-H), TP53-mutated, and no specific molecular profile (NSMP). In historical cohorts, age- and/or family history-directed screening was performed with MMR IHC. Statistical analysis was performed using a t-test for continuous variables and chi-square or Fisher's exact test for categorical variables.

RESULTS

In the NGS cohort, 38 subjects (27%) had MSI-H EC, 100 (71%) had microsatellite stable EC, and two (1%) had an indeterminate result. LS was diagnosed in two subjects (1%), and all but five patients completed genetic screening (96%). Molecular subtypes were ascertained: eight had POLE-ultramutated EC, 28 had TP53-mutated EC (20%), and 66 (47%) had NSMP. MSI-H and TP53-mutated EC had worse prognostic features compared with NSMP EC. Comparison with historical cohorts demonstrated a significant increase in follow-up testing after an initial positive genetic screen in the MSI NGS cohort (56% v 89%; P = .001).

CONCLUSION

MSI by NGS allowed for simultaneous screening for LS and categorization of EC into molecular subtypes with prognostic and therapeutic implications.

Abstract PD5-01: PD5-01 Genomic and epigenomic BRCA alterations predict adaptive resistance and response to platinum-based therapy in triple negative breast cancer and ovarian carcinoma

Background. Homologous recombination deficiency (HRD), induced by germline and somatic BRCA1 or BRCA2 gene mutations (BRCAmut) and by BRCA1 promoter methylation (BRCA1meth), has been associated with better response to platinum agents in both triple negative breast cancer (TNBC) and ovarian carcinoma (OvCa). A major conundrum arising from recent studies is why patients with BRCA1meth cancers do more poorly compared to those with BRCAmut cancers given the biologically equivalent HRD in both states. Here, we address this question by performing detailed genomic analyses of primary TNBC and OvCa cohorts and through patient-derived xenografts (PDXs) and their derivative cell lines. Methods. Both new and publicly available cohorts of primary TNBC and OvCa encompassing 499 individuals treated with a combination of platinum and taxane chemotherapy were analyzed by whole genome and transcriptome sequencing as well as limited epigenetic analyses. A cohort of 43 PDX models of TNBC was genomically characterized and responses to both single agent platinum and docetaxel were evaluated in vivo. PDX longitudinal studies were performed to assess the dynamics of BRCA1 methylation following treatment. Results. Genomic analyses revealed that BRCA1mut and BRCA1meth cancers share the same pattern of BRCA1-linked genomic rearrangements. Nonetheless, in all four primary cancer cohorts examined we found that patients with BRCAmut cancers, but not those with BRCA1meth cancers, had significantly better response outcomes compared to those with BRCA proficient cancers. A separate analysis of PDX TNBCs with BRCA1 promoter methylation showed that PDXs derived from treatment naïve cancers had complete methylation of the BRCA1 promoter, whereas those derived from post-treatment cancers invariably had only partial methylation. Compared to PDXs with complete methylation, those with partial methylation had a lower response rate to in vivo platinum-based therapy, but not to docetaxel. Using single cell clonal expansions from BRCA1meth PDX models, we confirmed that partial methylation was the result of demethylation of one of the BRCA1 promoter alleles and not of the outgrowth of a non-methylated clone. Exposure of TNBC PDXs with complete methylation to a single course of platinum therapy resulted in the emergence of an unmethylated BRCA1 promoter allele, which associated with an increase in BRCA1 expression. We confirmed that platinum treatment results in progressive loss of BRCA1 methylation and restoration of BRCA1 expression in the clinical setting, by studying the BRCA1 status of a longitudinal series of four TNBC PDX models established from the same patient at different stages of her clinical history. Differential gene expression analysis revealed an increased immune transcriptional signal, especially an elevated M1 macrophage signature, associated with enhanced response to platinum therapy only in patients with BRCA proficient cancers, in both TNBC and OvCa. Integrating both the strength of this cancer immune signature and the presence of BRCA mutations resulted in more accurate predictions of response when compared to either HRD or BRCA status alone. Conclusions. These results suggest that unlike BRCAmut cancers, where BRCA deficiency is more genetically stable, BRCA1meth cancers are highly adaptive to genotoxin exposure resulting in demethylation of one allele, recovery of BRCA1 expression and acquired insensitivity to platinum. On the other end, a high immune transcriptional signature identifies patients with BRCA proficient cancers that are more likely to benefit from platinum therapy. Taken together, our study underscores the importance of characterizing molecular heterogeneity to optimize predictive precision in assigning response probabilities in TNBC and OvCa.

Citation Format: Francesca Menghi, Kalyan Banda, Pooja Kumar, Robert Straub, Lacey E. Dobrolecki, Isabel Rodriguez, Susan E. Yost, Harshpreet Chandok, Marc Radke, George Somlo, Yuan Yuan, Michael T. Lewis, Elizabeth Swisher, Edison Liu. PD5-01 Genomic and epigenomic BRCA alterations predict adaptive resistance and response to platinum-based therapy in triple negative breast cancer and ovarian carcinoma [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 PD5-01.

Socioeconomic Status and Interest in Genetic Testing in a US-Based Sample

Cancer is a significant burden, particularly to individuals of low socioeconomic status (SES). Genetic testing can provide information about an individual's risk of developing cancer and guide future screening and preventative services. However, there are significant financial barriers, particularly for individuals of low SES. This study used the Early Detection of Genetic Risk (EDGE) Study's patient baseline survey (n = 2329) to evaluate the relationship between socioeconomic status and interest in pursuing hereditary cancer genetic testing. Analysis was completed for two interest outcomes-overall interest in genetic testing and interest in genetic testing if the test were free or low cost. Many demographic and SES variables were predictors for interest in genetic testing, including education, income, and MacArthur Subjective Social Scale (SSS). After controlling for the healthcare system, age, and gender, having a higher education level and a higher household income were associated with greater general interest. Lower SSS was associated with greater interest in genetic testing if the test was free or low cost. If genetic testing is the future of preventative medicine, more work needs to be performed to make this option accessible to low-SES groups and to ensure that those services are used by the most underserved populations.

Cell-autonomous inflammation of BRCA1-deficient ovarian cancers drives both tumor-intrinsic immunoreactivity and immune resistance via STING

In this study, we investigate mechanisms leading to inflammation and immunoreactivity in ovarian tumors with homologous recombination deficiency (HRD). BRCA1 loss is found to lead to transcriptional reprogramming in tumor cells and cell-intrinsic inflammation involving type I interferon (IFN) and stimulator of IFN genes (STING). BRCA1-mutated (BRCA1mut) tumors are thus T cell inflamed at baseline. Genetic deletion or methylation of DNA-sensing/IFN genes or CCL5 chemokine is identified as a potential mechanism to attenuate T cell inflammation. Alternatively, in BRCA1mut cancers retaining inflammation, STING upregulates VEGF-A, mediating immune resistance and tumor progression. Tumor-intrinsic STING elimination reduces neoangiogenesis, increases CD8+ T cell infiltration, and reverts therapeutic resistance to dual immune checkpoint blockade (ICB). VEGF-A blockade phenocopies genetic STING loss and synergizes with ICB and/or poly(ADP-ribose) polymerase (PARP) inhibitors to control the outgrowth of Trp53-/-Brca1-/- but not Brca1+/+ ovarian tumors in vivo, offering rational combinatorial therapies for HRD cancers.

Abstract 534: Functional drug screening of organoids from ovarian cancer patients demonstrates clinical and genomic concordance and identifies novel therapeutic vulnerabilities

Background: Clinically approved targeted therapies for ovarian cancer patients are currently limited to PARP inhibitors and bevacizumab. To improve treatment outcomes, a precision medicine approach is crucial to match effective drugs to patient-specific genetic features and vulnerabilities. This study aimed to: (1) demonstrate the feasibility of performing high-throughput drug screens on fresh patient organoids using a CLIA-approved assay, (2) assess concordance of responses with genomic and clinical information, and (3) reveal novel biomarkers of response to approved/experimental drugs and insights into ovarian cancer biology.

Methods: From 2015 to 2020, 76 ovarian tumor samples were collected from 60 patients. To date, 50 evaluable samples were successfully screened at SEngine Precision Medicine. Drugs tested include a range of chemotherapies and targeted therapies that are FDA-approved or in clinical development, with an average of 61 drugs screened per assay (range: 6-135). Somatic and/or germline DNA sequencing is currently available for 30 samples. Sample collection, screening, and sequencing is ongoing.

Results: The cohort included ovarian cancer patients with high grade serous (65%), low grade serous (7%), unknown grade serous (7%), clear cell (7%), carcinosarcoma (5%), stromal (5%), endometrioid (2%) subtypes, and one of unknown pathology. Whole genome mutational analysis of 5 tumor-derived organoids and their original tumors demonstrated a high degree of similarity between the tumor-organoid pairs. We present prospective and retrospective evidence from at least 18 cases that organoid drug screening can accurately predict clinical response to chemotherapy and targeted therapies. We also report a patient with platinum resistant serous carcinoma who responded to ibrutinib treatment after screening identified the drug as having excellent response in this patient's organoids. Three months into treatment, the patient's CA125 level was reduced from 250 to 125U/ml. In samples with available genomic information, we demonstrate high concordance between drug sensitivity and known biomarkers, e.g. 83% of samples with known BRCA1/BRCA2 mutation or high HRDetect showed sensitivity to a PARP inhibitor. Further, organoid screening can identify unique targets for every patient beyond established genomic biomarkers. Subsets of patients responded exceptionally to BET (41%), HDAC (28%), WEE1 (24%), and BTK (11%) inhibitors, indicating potential for these targeted therapies in ovarian cancer.

Conclusions: The genomic and histopathological heterogeneity of ovarian cancer points to a need to evolve and prioritize the personalization of treatment. Our data demonstrates the utility of organoid based drug screening to nominate therapeutic options for individual patients with or without known genomic biomarkers.

Citation Format: Goldie Lui, Anne Richardson, Payel Chatterjee, Madison Pollastro, Mia Lints, Danielle Peretti, Rachele Rosati, Lauren Appleyard, Grace Durenberger, Robert Diaz, Kay Gurley, Isabella Stork, Adam Whitney, Katannya Kapeli, Hallie Swan, Yasin Memari, Helen Davies, Serena Nik-Zainal, Kalyan Banda, Heidi Gray, Barbara Goff, Elizabeth Swisher, Astrid Margossian, Christopher Kemp, Carla Grandori. Functional drug screening of organoids from ovarian cancer patients demonstrates clinical and genomic concordance and identifies novel therapeutic vulnerabilities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 534.

Inherited mutations in fallopian tube, ovarian and primary peritoneal carcinoma: Changes in diagnoses and mutational frequency over 20 years

OBJECTIVES

Women with fallopian tube carcinoma (FTC) are reported to have a higher frequency of inherited BRCA mutations than those with ovarian carcinoma (OC) or primary peritoneal carcinoma (PPC). We hypothesized that routine serial sectioning of fallopian tubes would increase the proportion of cases designated as FTC and change the frequency of inherited mutations between carcinoma types.

METHODS

Eight hundred and sixty-seven women diagnosed from 1998 to 2018 were enrolled at diagnosis into an institutional tissue bank. Germline DNA, available from 700 women with FTC (N = 124), OC (N = 511) and PPC (N = 65), was assessed using targeted capture and massively parallel sequencing for mutations in ovarian carcinoma susceptibility genes. Cases were divided between those prior to routine serial sectioning (1998-2008) and after (2009-2019), and the frequency of FTC and inherited mutations was assessed.

RESULTS

The proportion of carcinomas attributed as FTC after 2009 was 28% (128/465), significantly higher than before 2009 [5% (21/402), p < .0001, OR 6.9, 95% CI 4.3-11.2], with subsequent decreases in OC and PPC. In the sequenced group, overall inherited mutation frequency in FTC (24/124, 19%), OC (106/511, 21%, p = .42), and PPC (16/65, 25%, p = .25) were similar. Germline mutation rates in FTC were lower after 2009,16/107 cases (15%), compared to 8/17 cases (47.1%) before 2009 (p = .005, OR 0.20, 95% CI 0.06-0.64).

CONCLUSIONS

The prevalence of inherited mutations is similar in FTC compared to OC or PPC when using modern pathological assignment. Complete serial sectioning of fallopian tubes has significantly increased the diagnosis of FTC, and subsequently decreased the frequency of inherited mutations within this group.

Comparative genomics of high grade neuroendocrine carcinoma of the cervix

In order to improve treatment selection for high grade neuroendocrine carcinomas of the cervix (NECC), we performed a comparative genomic analysis between this rare tumor type and other cervical cancer types, as well as extra-cervical neuroendocrine small cell carcinomas of the lung and bladder. We performed whole exome sequencing on fresh-frozen tissue from 15 NECCs and matched normal tissue. We then identified mutations and copy number variants using standard analysis pipelines. Published mutation tables from cervical cancers and extra-cervical small cell carcinomas were used for comparative analysis. Descriptive statistical methods were used and a two-sided threshold of P < .05 was used for significance. In the NECC cohort, we detected a median of 1.7 somatic mutations per megabase (range 1.0-20.9). PIK3CA p.E545K mutations were the most frequency observed oncogenic mutation (4/15 tumors, 27%). Activating MAPK pathway mutations in KRAS (p.G12D) and GNAS (p.R201C) co-occurred in two tumors (13%). In total we identified PI3-kinase or MAPK pathway activating mutations in 67% of NECC. When compared to NECC, lung and bladder small cell carcinomas exhibited a statistically significant higher rate of coding mutations (P < .001 for lung; P = .001 for bladder). Mutation of TP53 was uncommon in NECC (13%) and was more frequent in both lung (103 of 110 tumors [94%], P < .001) and bladder (18 of 19 tumors [95%], P < .001) small cell carcinoma. These comparative genomics data suggest that NECC may be genetically more similar to common cervical cancer subtypes than to extra-cervical small cell neuroendocrine carcinomas of the lung and bladder. These results may have implications for the selection of cytotoxic and targeted therapy regimens for this rare disease.

Homologous recombination deficiency (HRD) by BROCA-HR and survival outcomes after surgery for patients (pts) with pancreatic adenocarcinoma (PC): A single institution experience

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Background: 5-7% of PC pts exhibit deleterious germline mutations (MUT) in HR tumor suppressor genes BRCA1 and BRCA2. BROCA-HR is a targeted capture and massively parallel sequencing assay designed to detect all mutation classes including gene rearrangements, copy number variations, and gene aberrations within the Fanconi Anemia-BRCA HR, non-homologous end joining (NHEJ) DNA repair, and DNA mismatch repair pathways. BROCA-HR has been successfully used in breast and ovarian cancer pts for overall prognosis and prediction of response to platinum-based therapies. While BRCA1/2 MUT may confer survival advantage for PC pts if treated with platinum-chemotherapy, the survival impact of HRD is less well defined. Methods: We retrospectively identified 100 consecutive pts who underwent surgical resection for suspected PC at University of Washington Medical Center between 1999 and 2008. Formalin-fixed paraffin embedded resected tumors were sequenced using BROCA-HR. HRD was grouped based on the following deleterious genetic mutations: 1) BRCA1, BRCA2; 2) core HRD: BARD1, BRIP1, RAD51C, RAD51D, PALB2, CDK12, NBN; 3) non-core HRD: ATM, ATR, ATRX, BAP1, BLM, CHEK1/2, ERCC, FANC A/C/D2/E /F/G/L, MRE11, RAD50/51/51B, RIF1, SLX4; 4) HR proficient. Overall survival (OS) was measured from diagnosis until death or last follow-up. Results: 95 pts had histologically confirmed PC, and 81 pts had adequate tumor DNA for analysis. Six pts (7%) had BRCA1/2 MUT (n = 5), or BRCA1 methylation (n = 1), 1 pt (1%) had non-BRCA core HRD ( PALB2 MUT), 7 pts (9%) had non-core HRD: ERCC (2), CHEK2 (2), ATR, RAD51D, and FANCA MUT (1 each). Median OS was: all pts 1.93 yrs (95% C.I. 1.53, 2.16), BRCA1/2 pts 3.09 yrs (95% CI 0.41, 12.21), all core HRD pts 1.21 yrs (95% CI 0.41, 12.21), all core and non-core HRD pts 1.89 yrs (95% CI 0.57, 4.96), HR proficient pts 1.93 yrs (95% CI 1.51, 2.15). There were no OS differences between pts with HRD vs those HR proficient. Conclusions: HRD is common (17%) but does not affect OS for pts with resected PC. Prospective clinical trials should test neo/adjuvant therapies including platinum chemotherapy and PARP inhibitors for pts with HRD.

Abstract GMM-048: CTDNA RESPONSE TO THE PARP INHIBITOR RUCAPARIB PREDICTS PROGRESSION-FREE SURVIVAL AND BEST OVERALL RESPONSE ON THE ARIEL2 TRIAL

BACKGROUND: High grade serous ovarian carcinoma (HGSOC) is characterized by ubiquitous TP53 mutation and has the highest genomic complexity of all epithelial neoplasms. Sensitivity to PARP inhibitor therapy is strongly associated with homologous recombination deficiency (HRD). Genomic biomarkers of HRD such as genome-wide loss of heterozygosity (LOH) scores predict HRD and response to rucaparib. We hypothesized that functional testing of response during PARP inhibitor treatment using changes in circulating tumour DNA (ctDNA) could improve prediction of patient outcome. We tested whether the change in ctDNA TP53 mutant allele fraction (MAF) after one cycle of rucaparib treatment was predictive of progression free survival (PFS) and response in patients from the phase 2 ARIEL2 trial in women with platinum-sensitive recurrent high grade ovarian cancer (NCT01891344).

METHODS: We analyzed serial plasma samples (n = 636) from 142 HGSOC patients during screening, on day 1 of each treatment cycle, and at the end of rucaparib treatment. Targeted amplicon deep sequencing (TADS) of TP53 was performed on DNA extracted from plasma (median depth 6916×). Somatic TP53 mutation and loss of heterozygosity score (LOH) were available from archival and biopsy specimens. Statistical analyses were pre-specified and ctDNA analysis was carried out blinded to visit and response data. TP53 MAF changes after one cycle of treatment were compared with PFS and best overall response assessed by RECIST v1.1 and GCIG CA-125 criteria. Optimal cut points for ctDNA response were determined using a cross-validation analysis. In cases with &gt;1 TP53 mutation, response assessment was performed using the mutation with highest MAF.

RESULTS: We detected TP53 mutations in plasma from 134 patients; all cases were concordant between tumour and plasma except for one patient (present in plasma but not tumour). In 18 patients (13%), 2 or more TP53 mutations were detected in ctDNA. The median TP53 MAF prior to cycle 1 was 2.6% (IQR 0.3–8.6). Reduction of &gt;70% of TP53 MAF in ctDNA between cycle 1 and 2 was significantly predictive of improved PFS (n = 97; HR = 0.53, 95% CI 0.34-0.85, p = 0.008, median 273 vs 158 days, sensitivity 76%, specificity 62%) and best overall response (n = 97; OR = 7.04, 95% CI 2.69–21.06, p &lt; 0.001). Combining ctDNA and LOH scores did not improve prediction of response.

CONCLUSIONS

Response measured by &gt;70% fall in TP53 ctDNA between pre-cycle 1 and pre-cycle 2 of rucaparib therapy was significantly associated with best overall response and improved PFS. Similar findings were observed in a retrospective study of recurrent HGSOC treated with standard of care chemotherapy. The pathological or genomic factors causing multiple TP53 mutations in ctDNA are unknown.

The association between early fall in ctDNA and validated RECIST and CA-125 response markers provides strong evidence that ctDNA may have utility for detecting early response to targeted therapy. Further analyses in randomized studies should be performed to confirm that ctDNA response has strong predictive value.

Citation Format: Anna Piskorz, David Robertson, Kevin K. Lin, James Morris, Elaina Mann, Amit Oza, Robert L. Coleman, David M. O'Malley, Michael Friedlander, Janiel M. Cragun, Ling Ma, Heidi Giordano, Iain A. McNeish, Elizabeth Swisher, James Wason, James D. Brenton. CTDNA RESPONSE TO THE PARP INHIBITOR RUCAPARIB PREDICTS PROGRESSION-FREE SURVIVAL AND BEST OVERALL RESPONSE ON THE ARIEL2 TRIAL [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr GMM-048.

ACTR-61. A RANDOMIZED PHASE 2 TRIAL OF CEDIRANIB IN COMBINATION WITH OLAPARIB VERSUS BEVACIZUMAB IN PATIENTS WITH RECURRENT GLIOBLASTOMA

BACKGROUND

Like most proliferating tumors, GBM relies heavily on accurate DNA repair for maintenance of genome stability. Dysfunction in repair of both single and double strand DNA breaks by PARP inhibition and impairment of homologous recombination, respectively, would be synthetically lethal. In this study we combined the PARP inhibitor olaparib with cediranib, a pan VEGF receptor inhibitor. Cediranib may mediate disruption in the homologous recombination pathway through its antiangiogenic properties.

METHODS

Through the Experimental Therapeutics Clinical Trials Network, we performed an open-label randomized phase II study of bevacizumab (BEV)- naive adult patients with first or second recurrence of glioblastoma after radiation and temozolomide. Patients were randomized 1:1 to receive either olaparib 200 mg by mouth twice daily with cediranib 30 mg by mouth daily or BEV 10 mg/kg IV every 2 weeks. The primary endpoint was progression-free survival at 6 months (PFS6). Secondary endpoints included safety and overall survival. Exploratory objectives included blood, tissue and imaging-based biomarkers of response to treatment.

RESULTS

Seventy patients were enrolled. Median age was 60.5 years (range: 19–79), 39% females, median KPS was 90 (range: 60–100). Baseline characteristics were well balanced. With a data cut-off of 5/2/2019, PFS6 was 14% [95% CI 4–30%] in the cediranib/olaparib arm vs 30.9% [95% CI 12.7–51.2%] in the BEV arm. Median OS was 247 days in the cediranib/olaparib arm vs 201 days in the BEV arm, HR 0.816, 95% CI (0.431, 1.546). Related grade 3, 4 or 5 toxicity was experienced in 29% vs 12% of patients for the cediranib/olaparib vs BEV arm.

CONCLUSION

Treatment with cediranib/olaparib failed to increase PFS and OS in patients with recurrent GBM. Blood, tissue and imaging correlates will be presented to help understand why this treatment combination was unsuccessful.

A case of metastatic dysgerminoma treated with two cycles neoadjuvant chemotherapy followed by fertility-sparing minimally invasive surgery

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Neoadjuvant chemotherapy (NACT) followed by fertility-sparing surgery is a feasible treatment of metastatic dysgerminoma

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As few as two cycles of NACT may result in enough of a tumor response for fertility-sparing surgery to be possible.

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Tumor lysis syndrome is a possibility when administering chemotherapy to patients with metastatic dysgerminoma

NCCN Guidelines Insights: Genetic/Familial High-Risk Assessment: Breast and Ovarian, Version 2.2017

The NCCN Clinical Practice Guidelines in Oncology for Genetic/Familial High-Risk Assessment: Breast and Ovarian provide recommendations for genetic testing and counseling for hereditary cancer syndromes and risk management recommendations for patients who are diagnosed with a syndrome. Guidelines focus on syndromes associated with an increased risk of breast and/or ovarian cancer. The NCCN Genetic/Familial High-Risk Assessment: Breast and Ovarian panel meets at least annually to review comments from reviewers within their institutions, examine relevant new data from publications and abstracts, and reevaluate and update their recommendations. The NCCN Guidelines Insights summarize the panel's discussion and most recent recommendations regarding risk management for carriers of moderately penetrant genetic mutations associated with breast and/or ovarian cancer.

Abstract LB-329: MicroRNA profiling to identify novel determinants of platinum resistance in BRCA1/2-mutated high-grade serous ovarian cancer

Ovarian cancer is the fifth leading cause of mortality in women and the most lethal of all gynecologic tumors. Patients with high grade serous ovarian carcinoma (HGSOC) have poor prognosis due to a combination of factors including lack of early detection and failure of therapeutic regimens. Approximately 50% of all ovarian tumors have germline/somatic mutations or epigenetic alterations in genes making up the homologous recombination (HR) pathway. The resultant “BRCAness” phenotype pre-disposes these tumors to an improved response from current ovarian cancer therapies i.e. platinum therapy and PARP inhibitors. Despite the predicted synthetic lethality, a majority of patients with recurrent ovarian cancer eventually develop resistance. A detailed understanding of clinically relevant mechanisms of chemotherapy resistance is an important step in improving disease outcomes.

To systematically identify microRNA (miRNA) mediators of chemo-resistance in HGSOC, we performed small RNA sequencing of 38 BRCA mutated tumors with known response to platinum chemotherapy and identified three miRNA’s: miR-139-5p, miR-493-5p and miR-494-3p that were significantly overexpressed in platinum resistant compared to the platinum sensitive tumors. Overexpression of these candidate miRNA’s was associated with worse overall outcome among BRCA1/2-mutated tumors in the TCGA dataset. Interestingly, overexpression of miR-493-5p only correlated with poor progression free survival in BRCA2 mutant tumors and not BRCA1 mutant tumors. Importantly, overexpression of miR-493-5p was also identified in 13 out of 40 olaparib resistant tumors in KB2P BRCA2 deficient mouse models. Additionally, overexpression of miR-493-5p in BRCA2 mutated HGSOC cell-lines induced resistance to cisplatin and olaparib in vitro. Mechanistically, resistance mediated by miR-493-5p was not associated with restoration of HR (as evaluated by restoration of Rad51 foci) but was rather related to replication fork stabilization. Identification of specific targets of miR-493-5p is currently underway. In summary, overexpression of miR-493-5p may be a novel mechanism of resistance to platinum and PARP-inhibitors in BRCA2-mutated ovarian cancers and may serve as a biomarker of response to these agents in BRCA2 mutated ovarian tumors. Inhibition of miR-493-5p may be a novel strategy to resensitize chemo-resistant BRCA2 mutated tumors to platinum therapy and PARP-inhibitors.

Citation Format: Khyati Meghani, Ewa Gogola, Sven Rottenberg, Jos Jonkers, Ursula Matulonis, Elizabeth Swisher, Panagiotis Konstantinopoulos, Dipanjan Chowdhury. MicroRNA profiling to identify novel determinants of platinum resistance in BRCA1/2-mutated high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-329. doi:10.1158/1538-7445.AM2017-LB-329

Abstract AP28: BRCA1 and RAD51C Promoter Hypermethylation Confer Sensitivity to PARP Inhibitors in Patients with Platinum Sensitive Ovarian Carcinoma

Germline and somatic mutations in BRCA1 and BRCA2 (BRCA) confer PARP inhibitor sensitivity. Promoter hypermethylation is an alternate mechanism of gene down-regulation, and BRCA1 promoter methylation is relatively common in sporadic ovarian cancer. The clinical significance of BRCA1 methylation is less clear than for mutations, as the Cancer Genome Atlas (TCGA) and others have failed to show improved survival in ovarian carcinomas with BRCA1 methylation. No one has previously tested whether BRCA1 methylation confers in vivo sensitivity to PARP inhibitors in patients with ovarian cancer. ARIEL2 is a phase 2 study of the PARP inhibitor rucaparib in patients with recurrent platinum sensitive high-grade ovarian, peritoneal or fallopian tube carcinoma. At enrollment, ARIEL2 required pre-treatment tumor biopsies with the goal of developing tissue predictors of PARP inhibitor sensitivity other than BRCA mutations. The number of women with known germline mutations was capped at 15 patients in order to predominantly enroll BRCA wildtype cases. As presented at ASCO 2016, in cases with no BRCA mutations, a high fraction of genomic loss of heterozygosity (LOH) significantly predicted a better progression-free survival (the primary endpoint), longer duration of response, and a higher fraction of responders compared to cases with low LOH. We assessed BRCA1 and RAD51C promoter hypermethylation using methylation-sensitive polymerase chain reaction in paired archival and pre-treatment biopsies from patients on ARIEL2. Of 165 cases for which methylation analyses were completed, 21 (12.7%) were methylated at the BRCA1 promoter and four (2.4%) at the RAD51C promoter. Methylation of BRCA1 and RAD51C was mutually exclusive with mutation in BRCA or other homologous recombination genes. All four cases with RAD51C methylation and 15/19 (78.9%) with BRCA1 methylation were associated with high LOH. In 90 paired samples archival and pre-treatment tissues, RAD51C methylation was 100% concordant and BRCA1 methylation was highly concordant (p&lt;0·001). For 13 cases with BRCA1 methylation in the archival specimen, 4 (30·8%) were unmethylated in the paired pretreatment tumor, but for 77 unmethylated archival specimens, gain of methylation in the pretreatment biopsy was observed just once. Confirmed RECIST responses were seen in 52.4% (11/21) BRCA1 methylated and 75.0% (3/4) RAD51C methylated cases. In conclusion, BRCA1 and RAD51C methylation in ovarian carcinomas correlates with a high response rate to PARP inhibitors. If methylation was to be used as a predictor of PARP inhibitor sensitivity, it would need to be assessed in a pre-treatment (not archival) specimen. The loss of BRCA1 methylation in recurrent ovarian carcinoma, which was common even in these platinum sensitive cases, could explain why BRCA1 methylation is associated with similar survival to methylated cases, despite initial improved therapeutic sensitivity.

Citation Format: Elizabeth Swisher, Maria Harrell, Kevin K. Lin, Clare Scott, Sandra Goble, Amit Oza, Robert L. Coleman, Gottfried Konecny, Anna V. Tinker, David M. O'Malley, Rebecca Kristeleit, Ling Ma, James Brenton, Katherine Bell-McGuinn, Ana Oaknin, Alexandra Leary, Elaina Mann, Heidi Giordano, Mitch Rapon, Iain McNeish, Scott H. Kaufmann. BRCA1 and RAD51C Promoter Hypermethylation Confer Sensitivity to PARP Inhibitors in Patients with Platinum Sensitive Ovarian Carcinoma [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP28.

Abstract DPOC-004: MAGENTA: MAking GENetic Testing more Accessible

The standard paradigm for cancer susceptibility genetic testing has been for patients to 1) be identified by their provider as being at high risk due to extensive family history or another diagnosis (e.g., breast cancer for ovarian risk testing), and 2) attend in–person pre and post– genetic test sessions with a genetic counselor to prepare for testing and learn about the results. This arrangement places boundaries around the types of women willing to spend this time and effort receiving testing, as providers are required to act as gatekeepers to the testing process. More open methods of accessing genetic testing and providing support need to be evaluated.

We propose to deliver personal, risk–based genetic testing and results to women from the general public using the Internet. Internet–based services offer several advantages over either in–person or telephone interventions. First, information can be accessed by participants and providers on their own schedules, at any location with internet access, and can be consumed at the pace and style that is best for individual tastes and styles. If necessary, information and support can be re–reviewed if the patient does not remember the initial counseling session. Second, delivery of information through the internet can be performed in a more efficient and cost–effective manner, reserving the limited in–person genetic counseling for individuals who need it the most, while providing support to the general public about basic medical and risk–based information. Recruitment via social media outlets can directly link potential participants to the Internet systems that screen for eligibility and provide testing support. Finally, Internet delivery can bring genetic testing to the patient in their home, eliminating a major barrier to testing (multiple visits to the provider)

The main objective of MAGENTA is to test the effects of on–line genetic education versus telephone genetic counseling on cancer distress and other psychological outcomes. We will recruit women using social media and other eHealth methods to participate in a randomized trial of ovarian cancer counseling and testing that is conducted online and using the telephone. We will conduct a (2x2 factorial design) randomized trial to test online versus telephone pre– and post–test genetic counseling for ovarian cancer risk among women at higher than average risk for ovarian cancer. We expect to enroll 3000 women through our media contacts to participate in MAGENTA. For genetic risk assessment, we will evaluate and provide feedback on 19 breast and ovarian cancer (OC) genes that have a clear relationship to cancer risk in collaboration with Color Genomics. Variants include ATM, BARD1, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, EPCAM, MSH2, MSH6, MLH1, NBN, PALB2, PMS2, PTEN, RAD51C, RAD51D, TP53, and STK1. We will follow women for main psychological outcomes at 3 months post testing and longer for other outcomes.

Citation Format: Swisher E., Lu K., Bowen DJ, Gavin K. MAGENTA: MAking GENetic Testing more Accessible [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr DPOC-004.

Abstract AP27: FEASIBILITY OF MONITORING RESPONSE TO THE PARP INHIBITOR RUCAPARIB WITH TARGETED DEEP SEQUENCING OF CIRCULATING TUMOR DNA (CTDNA) IN WOMEN WITH HIGH GRADE OVARIAN CARCINOMA ON THE ARIEL2 TRIAL

BACKGROUND: TP53 mutations are present in &gt;97% cases of high-grade serous ovarian cancer (HGSOC). Detection of TP53 mutations in ctDNA extracted from plasma has the potential to monitor disease course and treatment response. We have developed targeted amplicon deep sequencing (TADS) to detect low frequency mutations throughout the TP53 gene in ctDNA. Rucaparib is a PARP inhibitor in development for treatment of tumors with HR pathway deficiency. We used TADS to assess TP53 mutant allele fraction (MAF) in ctDNA from patients in ARIEL2, a phase 2 study of rucaparib for treatment of relapsed high-grade ovarian cancer (NCT01891344).

MATERIAL AND METHODS: Plasma samples (n=65) from 18 patients were collected during screening, on day 1 of each cycle, and at the end of rucaparib treatment. DNA extracted from plasma underwent TADS of TP53 (median depth 6916×). FFPE tumor specimens were profiled using an NGS-based assay with a targeted gene panel including TP53. Investigator-assessed clinical response rates were evaluated by RECIST v1.1 and GCIG CA-125 criteria.

RESULTS: Concordant TP53 mutations were detected in tumor and ctDNA from plasma for all 18 patients. Median TP53 MAF at screening and cycle 1 day 1 was 5.1% (interquartile range: 1.1–17.5, n=16) and 3.8% (IQR: 0.68–10.3, n=16), respectively. Fourteen patients were evaluable for response measured by quantification of TP53 MAF between cycle 1 and 2 (missing sample: n=2; TP53 MAF &lt;0.5%; n=2). 7/9 patients with &gt;50% reduction of TP53 MAF in ctDNA at cycle 2 achieved a RECIST confirmed PR (see Table); this included 5/6 patients with either a germline or somatic mutation in BRCA1/BRCA2. No patients with &lt;50% reduction at cycle 2 (n=5) achieved a RECIST response.

CONCLUSIONS: Noninvasive detection of TP53 mutations by TADS is feasible, using plasma samples collected from women with relapsed platinum-sensitive high-grade ovarian cancer participating in an international multicenter trial. Circulating tumor DNA is a promising biomarker for monitoring response to the PARP inhibitor rucaparib. We are now testing the pre-specified hypothesis that a &gt;50% reduction in TP53 MAF between baseline and cycle 2 is predictive of response to rucaparib using 560 plasma samples from 139 ARIEL2 subjects. Updated results will be presented at the meeting.

Citation Format: Anna Piskorz, Kevin K. Lin, James Morris, Elaina Mann, Amit Oza, Robert L. Coleman, David M. O'Malley, Michael Friedlander, Janiel M. Cragun, Ling Ma, Heidi Giordano, Nitzan Rosenfeld, Mitch Raponi, Iain A. McNeish, Elizabeth Swisher, James D. Brenton. FEASIBILITY OF MONITORING RESPONSE TO THE PARP INHIBITOR RUCAPARIB WITH TARGETED DEEP SEQUENCING OF CIRCULATING TUMOR DNA (CTDNA) IN WOMEN WITH HIGH GRADE OVARIAN CARCINOMA ON THE ARIEL2 TRIAL [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP27.

ARIEL4: An international, multicenter randomized phase 3 study of the PARP inhibitor rucaparib vs chemotherapy in germline or somatic BRCA1- or BRCA2-mutated, relapsed, high-grade ovarian carcinoma

TPS5603

Background: In high-grade epithelial ovarian carcinoma (OC), ≈18% of patients (pts) have tumors with a germline BRCA1 or BRCA2 mutation; ≈7% have tumors with a somatic BRCA1 or BRCA2 mutation (Pennington et al. Clin Cancer Res. 2014;20:764-75). The poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib is approved in the United States for treatment of pts with OC associated with a deleterious BRCA1 or BRCA2 mutation (germline and/or somatic) who have received ≥2 chemotherapies. Although PARP inhibitors have demonstrated clinical activity in OC in both treatment and maintenance settings, comparison to standard of care (SOC) has only been evaluated in the maintenance setting. Randomized studies are needed to assess the benefit-risk profile of PARP inhibitors vs current SOC as treatment for BRCA1- or BRCA2-mutated, relapsed, high-grade OC. Methods: ARIEL4 (NCT02855944) is evaluating rucaparib vs chemotherapy as treatment for pts with germline or somatic BRCA1- or BRCA2-mutated, relapsed, high-grade OC (regardless of histology) who have received ≥2 prior chemotherapy regimens. Approximately 345 pts will be randomized 2:1 to receive rucaparib (600 mg BID) (n = 230) or chemotherapy (n = 115) and stratified by progression-free interval after their most recent platinum regimen. Pts with platinum-resistant (progressive disease [PD] 1– < 6 mo after last platinum) or partially platinum-sensitive disease (PD 6– < 12 mo after last platinum) will be randomized to rucaparib or weekly paclitaxel; pts with platinum-sensitive disease (PD ≥12 mo after last platinum) will be randomized to rucaparib or platinum-based therapy (single-agent or doublet at the discretion of the investigator). Pts receiving chemotherapy have the option to cross over to rucaparib upon radiographic disease progression. The primary endpoint is progression-free survival. Secondary endpoints include investigator-assessed objective response rate (ORR) (RECIST version 1.1), ORR/CA-125 response, duration of response, overall survival, and pt-reported outcomes. Safety will be summarized descriptively using standard adverse event reporting. Clinical trial information: NCT02855944.

Small cell ovarian carcinoma: Long term survival in juvenile case with poor prognostic features

Background

Ovarian small cell carcinoma is a rare, aggressive neoplasm that occurs in young women and has a poor long-term prognosis. Treatment involves surgical resection and chemotherapy. The required radicality of surgery is uncertain, balancing cytoreduction with fertility preservation. Various chemotherapy regimens are utilized due to confusion regarding the neoplasm's lineage.

Case

We describe an adolescent with small cell carcinoma, hypercalcemic type, stage IA. Surgery included left salpingo-oopherectomy, left pelvic/paraaortic lymphadenectomy, omentectomy and peritoneal biopsies. She received four cycles of bleomycin, etoposide and cisplatin, similar to high-risk germ cell cancers. She has received no further therapy and is eleven years from diagnosis without evidence of disease.

Conclusion

This is the first long-term juvenile survivor managed with both fertility-sparing surgery and BEP (bleomycin, etoposide, cisplatin).

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SCCO can be treated with less-toxic chemotherapy directed at germ cell tumors.

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Fertility-sparing surgery should be considered in adolescents with early stage SCCO.

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Long term survival in adolescents with SCCO is possible.

Genetic/Familial High-Risk Assessment: Breast and Ovarian, Version 2.2015

The NCCN Guidelines for Genetic/Familial High-Risk Assessment: Breast and Ovarian provide recommendations for genetic testing and counseling and risk assessment and management for hereditary cancer syndromes. Guidelines focus on syndromes associated with an increased risk of breast and/or ovarian cancer and are intended to assist with clinical and shared decision-making. These NCCN Guidelines Insights summarize major discussion points of the 2015 NCCN Genetic/Familial High-Risk Assessment: Breast and Ovarian panel meeting. Major discussion topics this year included multigene testing, risk management recommendations for less common genetic mutations, and salpingectomy for ovarian cancer risk reduction. The panel also discussed revisions to genetic testing criteria that take into account ovarian cancer histology and personal history of pancreatic cancer.

Phase I Study of Veliparib (ABT-888) Combined with Cisplatin and Vinorelbine in Advanced Triple-Negative Breast Cancer and/or BRCA Mutation-Associated Breast Cancer

PURPOSE

Cisplatin is synergistic with vinorelbine and the PARP inhibitor veliparib, and has antineoplastic activity in triple-negative breast cancer (TNBC) and BRCA mutation-associated breast cancer. This phase I study assessed veliparib with cisplatin and vinorelbine.

EXPERIMENTAL DESIGN

A 3+3 dose-escalation design evaluated veliparib administered twice daily for 14 days with cisplatin (75 mg/m(2) day 1) and vinorelbine (25 mg/m(2) days 1, 8) every 21 days, for 6 to 10 cycles, followed by veliparib monotherapy. Pharmacokinetics, measurement of poly(ADP-ribose) in peripheral blood mononuclear cells, and preliminary efficacy were assessed. IHC and gene-expression profiling were evaluated as potential predictors of response.

RESULTS

Forty-five patients enrolled in nine dose cohorts plus five in an expansion cohort at the highest dose level and recommended phase II dose, 300 mg twice daily. The MTD of veliparib was not reached. Neutropenia (36%), anemia (30%), and thrombocytopenia (12%) were the most common grade 3/4 adverse events. Best overall response for 48 patients was radiologic response with 9-week confirmation for 17 (35%; 2 complete, 15 partial), and stable disease for 21 (44%). Germline BRCA mutation presence versus absence was associated with 6-month progression-free survival [PFS; 10 of 14 (71%) vs. 8 of 27 (30%), mid-P = 0.01]. Median PFS for all 50 patients was 5.5 months (95% confidence interval, 4.1-6.7).

CONCLUSIONS

Veliparib at 300 mg twice daily combined with cisplatin and vinorelbine is well tolerated with encouraging response rates. A phase II randomized trial is planned to assess veliparib's contribution to cisplatin chemotherapy in metastatic TNBC and BRCA mutation-associated breast cancer. Clin Cancer Res; 22(12); 2855-64. ©2016 AACR.

Abstract A11: NGS-based tumor genomic profiling to identify ovarian cancer patients who benefit from the PARP inhibitor rucaparib

Background: PARP inhibitors (PARPi) are synthetically lethal to tumor cells with homologous recombination deficiency (HRD). HRD can result from deleterious BRCA1/2 mutations (BRCAmut) or other mechanisms that have not been fully elucidated. Regardless of mechanism, HRD leads to a common phenotype of genome-wide loss of heterozygosity (LOH). It has been hypothesized that this genomic phenotype can be used to identify BRCA wild-type (BRCAwt) HRD tumors likely sensitive to PARPi. Using comprehensive next generation sequencing (NGS)-based tumor genomic profiling, we developed an HRD assay for potential use as a companion diagnostic for rucaparib in high-grade ovarian cancer (HGOC) by combining tumor BRCA1/2 status and quantification of genomic LOH.

Methods: In the phase 2 study ARIEL2 Part 1 (NCT01891344), pre-treatment screening biopsies and archival formalin-fixed paraffin embedded tumor specimens were profiled using Foundation Medicine's NGS-based HRD assay, which detects all classes of genomic alterations, including base substitutions, insertions/deletions, and homozygous deletions in BRCA1/2. Genomic LOH was assessed by sequencing &gt;3,500 evenly-distributed single nucleotide polymorphisms across the genome and quantifying the extent of genomic LOH. A pre-specified genomic LOH cutoff was determined using publicly available SNP array data of ovarian tumors to predict platinum sensitivity as a surrogate marker for PARPi sensitivity. Response was assessed by RECIST v1.1 and GCIG CA-125 response criteria.

Results: As of July 1 2015, 195 archival tumor and 152 screening biopsy samples (142 matched pairs) from 206 HGOC patients enrolled (204 patients treated) in ARIEL2 Part 1 were successfully profiled using the NGS-based HRD assay. Some screening biopsies were not suitable for successful NGS-based HRD assessment primarily because of insufficient tumor nuclei or inadequate tumor volume. Most matched pairs of archival and pre-trial screening samples exhibited similar genomic LOH profiles (r=0.86); however, 14% of screening samples had higher genomic LOH compared with archival samples collected more than one year earlier. All BRCA1/2 germline and somatic mutated tumors had high genomic LOH in the screening samples. Receiver operating characteristic analysis of genomic LOH showed utility in identifying RECIST/CA-125 responders to rucaparib (AUC=0.72, p&lt;1e-4), with slightly better predictive utility using screening samples compared to archival samples (AUC=0.72 vs 0.69). Using the pre-specified genomic LOH cutoff, high genomic LOH tumors were detected in 54% of evaluable BRCAwt patients; significantly different overall response rates were found in patients with high vs low genomic LOH tumors (48% vs 26%; chi-square p=0.0074).

Conclusions: We developed an NGS-based HRD assay that assesses tumor BRCA1/2 and genomic LOH to prospectively identify HGOC patients who may benefit from rucaparib treatment. The optimized NGS-based HRD assay will be prospectively tested in the ongoing portion of the phase 2 study (ARIEL2 Part 2, NCT01891344) and a phase 3 maintenance study (ARIEL3, NCT01968213) that will investigate rucaparib in HGOC.

Citation Format: Iain A. McNeish, Kevin K. Lin, James X. Sun, Sandra Goble, Amit Oza, Robert L. Coleman, Clare L. Scott, Gottfried Konecny, Anna V. Tinker, David M. O'Malley, Rebecca Kristeleit, Ling Ma, James D. Brenton, Katherine Bell-McGuinn, Ana Oaknin, Alexandra Leary, Elaina Mann, Heidi Giordano, Roman Yelensky, Mitch Raponi, Elizabeth Swisher. NGS-based tumor genomic profiling to identify ovarian cancer patients who benefit from the PARP inhibitor rucaparib. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A11.

Abstract AS09: Germline mutations in cancer susceptibility genes in BRCA1 and BRCA2 negative families with ovarian and breast cancer

Objectives: Germline mutations in cancer susceptibility genes other than BRCA1 and BRCA2 (BRCA1/2) are found in approximately 6% of women with ovarian, fallopian tube, or primary peritoneal cancer. Our objective was to sequence BRCA1/2-negative ovarian cancer patients with a family history of ovarian or breast cancer to identify inherited mutations that may explain the familial risk.

Methods: We used a targeted capture, massively parallel sequencing test called BROCA on ovarian cancer probands with a family history of ovarian or breast cancer, or a personal history of breast cancer. BROCA testing included all known breast and ovarian cancer genes. Only clear loss of function mutations were included. 118 probands were ascertained from a gynecologic oncology tissue bank or outside referrals and provided informed consent. A family history of ovarian cancer was defined as having a first or second degree relative with ovarian cancer. A family history of breast cancer was defined as having a first or second degree relative with pre-menopausal breast cancer, or 2 or more regardless of menopausal status. Subjects were only included in one category.

Results: Of 118 ovarian cancer probands, 22 (18.6%) were found to carry deleterious mutations in non-BRCA1/2 cancer susceptibility genes. 8/29 (27.6%) ovarian cancer patients with a personal history of breast cancer had mutations in 7 genes (2 CHEK2, 2 RAD51D, 1 BRIP1, 1 TP53, 1 ATM, and one with both PALB2 and PMS2). This included mutations found in 2/5 (40%) who also had a family history of ovarian cancer and 4/10 (40%) who also had a family history of breast cancer. 38 patients had a family history of ovarian cancer with no personal history of breast cancer; 9/38 (23.7%) had mutations in 5 genes (3 BRIP1, 3 RAD51C, 1 RAD51D, 1 TP53, and 1 ATM). Finally, 5/51 (9.8%) ovarian cancer patients with a family history of breast cancer and no personal history of breast cancer had mutations in 5 genes (1 MSH6, 1 FAM175A, 1 NBN, 1 PALB2, and 1 CHEK2).

Conclusions: Germline mutations in DNA-repair genes are present in a substantial fraction of BRCA1/2-negative ovarian cancer patients with a personal or family history suggestive of inherited disease. These women may benefit from multiplex gene testing. The detection of inherited mutations in these women may be useful to identify the risk of other cancers, to inform family members of possible risk, and to direct therapy by suggesting candidates for PARP inhibitor therapy.

Citation Format: B. Norquist, M. Harrell, T. Walsh, J. Mandell, S. Bernards, K. Agnew, M. Lee, K. Pennington, M.C. King, E. Swisher. Germline mutations in cancer susceptibility genes in BRCA1 and BRCA2 negative families with ovarian and breast cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS09.

Abstract 5467: BRCA1 N-terminal-deficient proteins provide PARP inhibitor and platinum resistance

Introduction: Tumors harboring BRCA1 mutations initially respond well to platinum and PARP inhibitor therapy; however, resistance invariably arises and is a major clinical problem. The BRCA1 185delAG allele is a common founder mutation located close to the protein translation start site, thought to produce a short peptide devoid of function.

Experimental procedures: In this study, we utilized the SUM1315MO2 breast cancer cell line that harbors a BRCA1 185delAG mutation to study mechanisms of PARP inhibitor and platinum resistance. SUM1315MO2 cells were cultured in the presence of increasing concentrations of the PARP inhibitor rucaparib or cisplatin until rucaparib resistant (RR) and cisplatin resistant (CR) clones emerged.

Results: DNA sequencing revealed that no BRCA1 gene reversion mutations were present in resistant cells. We next measured BRCA1 protein levels by Western blotting with antibodies specific for the N- and C-terminal domains of BRCA1. As a control, the wild-type BRCA1 protein expressed in MDA-MB-231 cells was detectable with both N- and C-terminal antibodies. In contrast, BRCA1 protein was undetectable in both SUM1315MO2 parental and resistant clones using the N-terminal specific antibody. However, the C-terminal specific antibody identified a more quickly migrating band of low abundance in parental cells, but with elevated expression in both RR and CR clones. We inferred that this protein was devoid of the extreme N-terminal RING domain-containing region that mediates interaction with BARD1. To investigate the functionality of the N-terminal truncated BRCA1 protein (Nt-BRCA1), we measured BRCA1 and RAD51 irradiation-induced focus formation by immunofluorescence. RR and CR clones demonstrated 2.25 - 2.75-fold increase (P = 0.024) in the number of cells with BRCA1 foci compared to parental cells. Similarly, we detected a 2 - 2.85-fold increase (P = 0.0325) in RAD51 foci formation in resistant clones compared to parental cells. Additionally, BRCA1 siRNA treated cells were 12- and 9-fold more sensitive to rucaparib compared to scrambled siRNA-treated control cells (P = 0.0002). Similarly, CR-1 cells treated with BRCA1 siRNAs were 1.56- and 1.7-fold more sensitive to cisplatin (P = 0.0346) compared to scrambled siRNA treated cells. Furthermore, N-terminal truncated BRCA1 proteins were detectable in a primary tumor from a germline BRCA1185delAG mutation carrier.

Conclusions: Taken together, these results provide evidence for a novel, mutation location-dependent mechanism of PARP inhibitor and platinum resistance.

Citation Format: Yifan Wang, Andrea Bernhardy, Emmanuelle Nicolas, Ryan Winters, Kathy Cai, Kelly Duncan, James Duncan, Maria Harrell, Elizabeth Swisher, Neil Johnson. BRCA1 N-terminal-deficient proteins provide PARP inhibitor and platinum resistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5467. doi:10.1158/1538-7445.AM2015-5467

Abstract 4670: A novel companion diagnostic predicts response to the PARP inhibitor rucaparib in ovarian cancer

Background: Genomic studies suggest that ∼50% of high-grade serous ovarian cancers (OC) have homologous recombination deficiency (HRD). Germline BRCA1/2 mutations (gBRCAmut) are expected to account for 1/3 of HRD in OC, and identification of non-gBRCAmut HRD tumors likely to respond to PARP inhibitors (PARPi) remains a challenge. Using comprehensive next generation sequencing (NGS)-based tumor genomic profiling, we developed a companion diagnostic HRD assay to predict sensitivity to the PARP inhibitor rucaparib by combining tumor BRCA1/2 status (germline and somatic) and genomic loss of heterozygosity (LOH). The HRD assay is being validated in a Phase 2 study (ARIEL2) and will be prospectively applied to the primary analysis of the ongoing Phase 3 study (ARIEL3) of rucaparib.

Methods: The HRD assay uses 50-200ng of DNA from tumor FFPE specimens, which undergoes sequencing library construction and hybrid-capture of all coding exons from 100s of cancer-related genes. Libraries are sequenced to high, uniform depth (&gt;500× unique coverage, Illumina® HiSeq) and data are processed by a customized pipeline that accurately detects all classes of genomic alterations, including BRCA1/2 base substitutions, indels, and homozygous deletions. Genomic LOH is assessed by a CGH-like analysis of sequencing coverage and &gt;3,500 genome-wide SNPs and a tumor is classified as HRD with either BRCA1/2 alteration or high genomic LOH (LOH+). Somatic/germline status of discovered BRCA1/2 alterations is assessed by a previously-presented computational approach (“SGZ”, AACR 2014 abstract #1893), and verified against medical records where available. ARIEL2 is an ongoing single-arm (n = 180), open-label study of rucaparib in recurrent, platinum-sensitive OC patients. The primary objective is to evaluate clinical activity of rucaparib among 3 prospectively defined subgroups: tumor BRCAmut, BRCAwt/LOH+ (“BRCAness”) and BRCAwt/LOH-. Response is determined by RECIST and/or GCIG-CA125 criteria.

Results: The HRD assay was performed on tumors from 121 patients, of whom 25% were found to be BRCA mutant (17 germline/12 somatic), 42% had the BRCAness signature (BRCAwt/LOH+), and 33% were biomarker negative (BRCAwt/LOH-). Efficacy data available for 61 patients revealed objective response rates (combined RECIST/CA125 criteria) at 70%, 40% and 8%, respectively. Responses were observed for all classes of genomic alterations, and in gBRCAmut and non-gBRCAmut tumors.

Conclusions: Preliminary clinical data indicates that the HRD assay identifies OC patients likely to respond to rucaparib and highlights the potential for innovative companion diagnostics enabled by comprehensive genomic profiling based on NGS.

Citation Format: James Sun, Iain McNeish, Robert L. Coleman, Amit Oza, Clare Scott, David M. O'Malley, Kevin K. Lin, Christine Burns, Christine Vietz, Philip J. Stephens, Murtaza Mehdi, Matthew Hawryluk, Heidi Giordano, Mitch Raponi, Lindsey Rolfe, Jeff Isaacson, Vincent A. Miller, Andrew Allen, Elizabeth Swisher, Roman Yelensky. A novel companion diagnostic predicts response to the PARP inhibitor rucaparib in ovarian cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4670. doi:10.1158/1538-7445.AM2015-4670