Homologous Recombination Repair Gene Mutations to Predict Olaparib Plus Bevacizumab Efficacy in the First-Line Ovarian Cancer PAOLA-1/ENGOT-ov25 Trial

Untapped Potential of Poly(ADP-Ribose) Polymerase Inhibitors: Lessons Learned From the Real-World Clinical Homologous Recombination Repair Mutation Testing

Background

Testing for homologous recombination deficiency (HRD) mutations is pivotal to assess individual risk, to proact preventive measures in healthy carriers and to tailor treatments for cancer patients. Increasing prominence of poly(ADP-ribose) polymerase (PARP) inhibitors with remarkable impact on molecular-selected patient survival across diverse nosologies, ingrains testing for BRCA genes and beyond in clinical practice. Nevertheless, testing strategies remain a question of debate. While several pathogenic BRCA1/2 gene variants have been described as founder pathogenic mutations frequently found in patients from Russia, other homologous recombination repair (HRR) genes have not been sufficiently explored. In this study, we present real-world data of routine HRR gene testing in Russia.

Methods

We evaluated clinical and sequencing data from cancer patients who had germline/somatic next-generation sequencing (NGS) HRR gene testing in Russia (BRCA1/2/ATM/CHEK2, or 15 HRR genes). The primary objectives of this study were to evaluate the frequency of BRCA1/2 and non-BRCA gene mutations in real-world unselected patients from Russia, and to determine whether testing beyond BRCA1/2 is feasible.

Results

Data of 2,032 patients were collected from February 2021 to February 2023. Most had breast (n = 715, 35.2%), ovarian (n = 259, 12.7%), pancreatic (n = 85, 4.2%), or prostate cancer (n = 58, 2.9%). We observed 586 variants of uncertain significance (VUS) and 372 deleterious variants (DVs) across 487 patients, with 17.6% HRR-mutation positivity. HRR testing identified 120 (11.8%) BRCA1/2-positive, and 172 (16.9%) HRR-positive patients. With 51 DVs identified in 242 formalin-fixed paraffin-embedded (FFPE), testing for variant origin clarification was required in one case (0.4%). Most BRCA1/2 germline variants were DV (121 DVs, 26 VUS); in non-BRCA1/2 genes, VUS were ubiquitous (53 DVs, 132 VUS). In silico prediction identified additional 4.9% HRR and 1.2% BRCA1/2/ATM/CHEK2 mutation patients.

Conclusions

Our study represents one of the first reports about the incidence of DV and VUS in HRR genes, including genes beyond BRCA1/2, identified in cancer patients from Russia, assessed by NGS. In silico predictions of the observed HRR gene variants suggest that non-BRCA gene testing is likely to result in higher frequency of patients who are candidates for PARP inhibitor therapy. Continuing sequencing efforts should clarify interpretation of frequently observed non-BRCA VUS.

Is the Homologous Recombination Repair Mutation Defined by a 15-Gene Panel Associated with the Prognosis of Epithelial Ovarian Cancer?

BACKGROUND

There is no consensus regarding the specific genes included in the homologous recombination repair (HRR) gene panel for identifying the HRR deficiency (HRD) status and predicting the prognosis of epithelial ovarian cancer (EOC) patients.

OBJECTIVE

We aimed to explore a 15-gene panel involving the HRR pathway as a predictive prognostic indicator in Chinese patients newly diagnosed with EOC.

PATIENTS AND METHODS

We reviewed the previously published reports about different HRR gene panels and prespecified the 15-gene panel. The genetic testing results in a 15-gene panel from 308 EOC patients diagnosed between 2014 and 2022 from six centers were collected. The association of clinicopathologic characteristics, the use of poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPis) and progression-free survival (PFS) with 15-gene panel HRR mutations (HRRm) status was assessed.

RESULTS

43.2% (133/308) of patients were determined to carry 144 deleterious HRRm, among which 68.1% (98/144) were germline mutations and 32.8% (101/308) were BRCA1/2 gene lethal mutations. The hazard ratio (HR) (95% confidence interval, CI) for PFS (HRRm v HRR wild type, HRRwt) using the 15-gene panel HRRm was 0.42 (0.28-0.64) at all stages and 0.42 (0.27-0.65) at stages IIIC-IV. However, a prognostic difference was observed only between the BRCA mutation group and the HRRwt group, not between the non-BRCA HRRm group and the HRRwt group. For the subgroups of patients not using PARPis, the HR (95% CI) was 0.41 (0.24-0.68) at stages IIIC-IV.

CONCLUSIONS

This study provides evidence that 15-gene panel HRRm can predict the prognosis of EOC, of these only the BRCA1/2 mutations, not non-BRCA HRRm, contribute to prognosis prediction. Among patients without PARPis, the HRRm group presented a better PFS. This is the first study of this kind in the Chinese population.

Prevalence of Homologous Recombination Deficiency Among Patients With Germline RAD51C/D Breast or Ovarian Cancer

Importance

RAD51C and RAD51D are involved in DNA repair by homologous recombination. Germline pathogenic variants (PVs) in these genes are associated with an increased risk of ovarian and breast cancer. Understanding the homologous recombination deficiency (HRD) status of tumors from patients with germline PVs in RAD51C/D could guide therapeutic decision-making and improve survival.

Objective

To characterize the clinical and tumor characteristics of germline RAD51C/D PV carriers, including the evaluation of HRD status.

Design, Setting, and Participants

This retrospective cohort study included 91 index patients plus 90 relatives carrying germline RAD51C/D PV (n = 181) in Spanish hospitals from January 1, 2014, to December 31, 2021. Genomic and functional HRD biomarkers were assessed in untreated breast and ovarian tumor samples (n = 45) from June 2022 to February 2023.

Main Outcomes and Measures

Clinical and pathologic characteristics were assessed using descriptive statistics. Genomic HRD by genomic instability scores, functional HRD by RAD51, and gene-specific loss of heterozygosity were analyzed. Associations between HRD status and tumor subtype, age at diagnosis, and gene-specific loss of heterozygosity in RAD51C/D were investigated using logistic regression or the t test.

Results

A total of 9507 index patients were reviewed, and 91 patients (1.0%) were found to carry a PV in RAD51C/D; 90 family members with a germline PV in RAD51C/D were also included. A total of 157 of carriers (86.7%) were women and 181 (55.8%) had received a diagnosis of cancer, mainly breast cancer or ovarian cancer. The most prevalent PVs were c.1026+5_1026+7del (11 of 56 [19.6%]) and c.709C>T (9 of 56 [16.1%]) in RAD51C and c.694C>T (20 of 35 [57.1%]) in RAD51D. In untreated breast cancer and ovarian cancer, the prevalence of functional and genomic HRD was 55.2% (16 of 29) and 61.1% (11 of 18) for RAD51C, respectively, and 66.7% (6 of 9) and 90.0% (9 of 10) for RAD51D. The concordance between HRD biomarkers was 91%. Tumors with the same PV displayed contrasting HRD status, and age at diagnosis did not correlate with the occurrence of HRD. All breast cancers retaining the wild-type allele were estrogen receptor positive and lacked HRD.

Conclusions and Relevance

In this cohort study of germline RAD51C/D breast cancer and ovarian cancer, less than 70% of tumors displayed functional HRD, and half of those that did not display HRD were explained by retention of the wild-type allele, which was more frequent among estrogen receptor-positive breast cancers. Understanding which tumors are associated with RAD51C/D and HRD is key to identify patients who can benefit from targeted therapies, such as PARP (poly [adenosine diphosphate-ribose] polymerase) inhibitors.

FSP1 inhibition enhances olaparib sensitivity in BRCA-proficient ovarian cancer patients via a nonferroptosis mechanism

Poly ADP-ribose polymerase inhibitors (PARPis) exhibit promising efficacy in patients with BRCA mutations or homologous repair deficiency (HRD) in ovarian cancer (OC). However, less than 40% of patients have HRD, it is vital to expand the indications for PARPis in BRCA-proficient patients. Ferroptosis suppressor protein 1 (FSP1) is a key protein in a newly identified ferroptosis-protective mechanism that occurs in parallel with the GPX4-mediated pathway and is associated with chemoresistance in several cancers. Herein, FSP1 is reported to be negatively correlated with the prognosis in OC patients. Combination therapy comprising olaparib and iFSP1 (a FSP1 inhibitor) strongly inhibited tumour proliferation in BRCA-proficient OC cell lines, patient-derived organoids (PDOs) and xenograft mouse models. Surprisingly, the synergistic killing effect could not be reversed by ferroptosis inhibitors, indicating that mechanisms other than ferroptosis were responsible for the synergistic lethality. In addition, cotreatment was shown to induce increased γH2A.X foci and to impair nonhomologous end joining (NHEJ) activity to a greater extent than did any single drug. Mass spectrometry and immunoprecipitation analyses revealed that FSP1 interacted with Ku70, a classical component recruited to and occupying the end of double-strand breaks (DSBs) in the NHEJ process. FSP1 inhibition decreased Ku70 PARylation, impaired subsequent DNA-PKcs recruitment to the Ku complex at DSB sites and was rescued by restoring PARylation. These findings unprecedentedly reveal a novel role of FSP1 in DNA damage repair and provide new insights into how to sensitize OC patients to PARPi treatment.

Identification of potentially actionable genetic variants in epithelial ovarian cancer: a retrospective cohort study

Ovarian cancer is the most lethal gynecologic malignancy, mainly due to late-stage diagnosis, frequent recurrences, and eventually therapy resistance. To identify potentially actionable genetic variants, sequencing data of 351 Belgian ovarian cancer patients were retrospectively captured from electronic health records. The cohort included 286 (81%) patients with high-grade serous ovarian cancer, 17 (5%) with low-grade serous ovarian cancer, and 48 (14%) with other histotypes. Firstly, an overview of the prevalence and spectrum of the BRCA1/2 variants highlighted germline variants in 4% (11/250) and somatic variants in 11% (37/348) of patients. Secondly, application of a multi-gene panel in 168 tumors revealed a total of 214 variants in 28 genes beyond BRCA1/2 with a median of 1 (IQR, 1-2) genetic variant per patient. The ten most often altered genes were (in descending order): TP53, BRCA1, PIK3CA, BRCA2, KRAS, ERBB2 (HER2), TERT promotor, RB1, PIK3R1 and PTEN. Of note, the genetic landscape vastly differed between the studied histotypes. Finally, using ESCAT the clinical evidence of utility for every genetic variant was scored. Only BRCA1/2 pathogenic variants were classified as tier-I. Nearly all patients (151/168; 90%) had an ESCAT tier-II variant, most frequently in TP53 (74%), PIK3CA (9%) and KRAS (7%). In conclusion, our findings imply that although only a small proportion of genetic variants currently have direct impact on ovarian cancer treatment decisions, other variants could help to identify novel (personalized) treatment options to address the poor prognosis of ovarian cancer, particularly in rare histotypes.

Top advances of the year: Ovarian cancer

Although cure rates remain low and effective screening strategies are elusive, the recent advances in systemic therapies over the past year highlighted in this review have prolonged survival for women with ovarian cancer. In 2022, the first antibody-drug conjugate for platinum-resistant ovarian cancer received accelerated US Food and Drug Administration (FDA) approval. Confirmatory studies examining the efficacy of mirvetuximab and other antibody-drug conjugates are underway. In the upfront setting, the first data establishing an overall survival benefit from poly(ADP-ribose) polymerase inhibitor maintenance was demonstrated after a 7-year follow-up period. In contrast, long-term updates from poly(ADP-ribose) polymerase inhibitor trials in the noncurative setting reported survival detriments, and the FDA withdrew the respective indications. Several trials attempted to improve upon the standard of care for platinum-sensitive ovarian carcinoma and those with rare ovarian cancer histologies (carcinosarcoma, clear cell carcinoma) but failed to demonstrate a clinically or statistically meaningful benefit. This leaves the open question of how to further optimize systemic therapy for advanced ovarian carcinoma to improve long-term survival and cure rates.

Pathogenic germline variants in non-BRCA1/2 homologous recombination genes in ovarian cancer: Analysis of tumor phenotype and survival

OBJECTIVE

To define molecular features of ovarian cancer (OC) with germline pathogenic variants (PVs) in non-BRCA homologous recombination (HR) genes and analyze survival compared to BRCA1/2 and wildtype (WT) OC.

METHODS

We included patients with OC undergoing tumor-normal sequencing (MSK-IMPACT) from 07/01/2015-12/31/2020, including germline assessment of BRCA1/2 and other HR genes ATM, BARD1, BRIP1, FANCA, FANCC, NBN, PALB2, RAD50, RAD51B, RAD51C, and RAD51D. Biallelic inactivation was assessed within tumors. Progression-free (PFS) and overall survival (OS) were calculated from pathologic diagnosis using the Kaplan-Meier method with left truncation. Whole-exome sequencing (WES) was performed in a subset.

RESULTS

Of 882 patients with OC, 56 (6.3%) had germline PVs in non-BRCA HR genes; 95 (11%) had BRCA1-associated OC (58 germline, 37 somatic); and 59 (6.7%) had BRCA2-associated OC (40 germline, 19 somatic). High rates of biallelic alterations were observed among germline PVs in BRIP1 (11/13), PALB2 (3/4), RAD51B (3/4), RAD51C (3/4), and RAD51D (8/10). In cases with WES (27/35), there was higher tumor mutational burden (TMB; median 2.5 [1.1-6.0] vs. 1.2 mut/Mb [0.6-2.6]) and enrichment of HR-deficient (HRD) mutational signatures in tumors associated with germline PALB2 and RAD51B/C/D compared with BRIP1 PVs (p < 0.01). Other features of HRD, including telomeric-allelic imbalance (TAI) and large-scale state transitions (LSTs), were similar. Although there was heterogeneity in PFS/OS by gene group, only BRCA1/2-associated OC had improved survival compared to WT OC (p < 0.01).

CONCLUSIONS

OCs associated with germline PVs in non-BRCA HR genes represent a heterogenous group, with PALB2 and RAD51B/C/D associated with an HRD phenotype.

Validation of the Clinical Use of GIScar, an Academic-developed Genomic Instability Score Predicting Sensitivity to Maintenance Olaparib for Ovarian Cancer

PURPOSE

The optimal application of maintenance PARP inhibitor therapy for ovarian cancer requires accessible, robust, and rapid testing of homologous recombination deficiency (HRD). However, in many countries, access to HRD testing is problematic and the failure rate is high. We developed an academic HRD test to support treatment decision-making.

EXPERIMENTAL DESIGN

Genomic Instability Scar (GIScar) was developed through targeted sequencing of a 127-gene panel to determine HRD status. GIScar was trained from a noninterventional study with 250 prospectively collected ovarian tumor samples. GIScar was validated on 469 DNA tumor samples from the PAOLA-1 trial evaluating maintenance olaparib for newly diagnosed ovarian cancer, and its predictive value was compared with Myriad Genetics MyChoice (MGMC).

RESULTS

GIScar showed significant correlation with MGMC HRD classification (kappa statistics: 0.780). From PAOLA-1 samples, more HRD-positive tumors were identified by GIScar (258) than MGMC (242), with a lower proportion of inconclusive results (1% vs. 9%, respectively). The HRs for progression-free survival (PFS) with olaparib versus placebo were 0.45 [95% confidence interval (CI), 0.33-0.62] in GIScar-identified HRD-positive BRCA-mutated tumors, 0.50 (95% CI, 0.31-0.80) in HRD-positive BRCA-wild-type tumors, and 1.02 (95% CI, 0.74-1.40) in HRD-negative tumors. Tumors identified as HRD positive by GIScar but HRD negative by MGMC had better PFS with olaparib (HR, 0.23; 95% CI, 0.07-0.72).

CONCLUSIONS

GIScar is a valuable diagnostic tool, reliably detecting HRD and predicting sensitivity to olaparib for ovarian cancer. GIScar showed high analytic concordance with MGMC test and fewer inconclusive results. GIScar is easily implemented into diagnostic laboratories with a rapid turnaround.

RediScore: Prospective validation of a pipeline for homologous recombination deficiency analysis

Tumors harboring homologous recombination deficiency (HRD) are considered optimal candidates for poly(ADP-ribose) polymerase 1 (PARP) inhibitor treatment. Such deficiency can be detected by analyzing breast cancer type (BRCA)1/2 gene mutations, as well as mutations in other genes of the homologous recombination pathway. The algorithmic measurement of the HRD effect by identifying genomic instability (GI) has been used as biomarker. As compared with the direct measurement of somatic gene alterations, this approach increases the number of patients who could benefit from PARP inhibitor treatment. In the present study, the performance of the Oncoscan CNV assay, accompanied by appropriate bioinformatic algorithms, was evaluated for its performance in GI calculation and was compared with that of a validated next-generation sequencing (NGS) test (myChoice HRD test). In addition, the clinical utility of the GI score (GIS) and BRCA1/2 tumor analysis were investigated in a cohort of 444 patients with ovarian cancer. For that reason, single nucleotide polymorphism (SNP) arrays and appropriate bioinformatics algorithms were used to calculate GIS in 29 patients with ovarian cancer with known GIS status using a validated NGS test. Furthermore, BRCA1/2 analysis results were compared between the aforementioned assay and the amplicon-based Oncomine™ BRCA Research Assay. BRCA1/2 analysis was performed in 444 patients with ovarian cancer, while GIS was calculated in 175 BRCA1/2-negative cases. The bioinformatics algorithm developed for GIS calculation in combination with NGS BRCA1/2 analysis (RediScore), and the OncoscanR pipeline exhibited a high overall agreement with the validated test (93.1%). In addition, the Oncomine NGS assay had a 100% agreement with the validated test. The BRCA1/2 mutation frequency was 26.5% in the examined patients with ovarian cancer. GIS was positive in 40% of the BRCA1/2-negative cases. The RediScore bioinformatics algorithm developed for GIS calculation in combination with NGS BRCA1/2 analysis is a viable and effective approach for HRD calculation in patients with ovarian cancer, offering a positive prediction for PARP inhibitor responsiveness in 55% of the patients.

Shallow whole genome sequencing approach to detect Homologous Recombination Deficiency in the PAOLA-1/ENGOT-OV25 phase-III trial

The bevacizumab (bev)/olaparib (ola) maintenance regimen was approved for BRCA1/2-mutated (BRCAmut) and Homologous Recombination Deficient (HRD) high-grade Advanced Ovarian Cancer (AOC) first line setting, based on a significantly improved progression-free survival (PFS) compared to bev alone in the PAOLA-1/ENGOT-ov25 trial (NCT02477644), where HRD was detected by MyChoice CDx PLUS test. The academic shallowHRDv2 test was developed based on shallow whole-genome sequencing as an alternative to MyChoice. Analytical and clinical validities of shallowHRDv2 as compared to MyChoice on 449 PAOLA-1 tumor samples are presented. The overall agreement between shallowHRDv2 and MyChoice was 94% (369/394). Less non-contributive tests were observed with shallowHRDv2 (15/449; 3%) than with MyChoice (51/449; 11%). Patients with HRD tumors according to shallowHRDv2 (including BRCAmut) showed a significantly prolonged PFS with bev+ola versus bev (median PFS: 65.7 versus 20.3 months, hazard ratio (HR): 0.36 [95% CI: 0.24-0.53]). This benefit was significant also for BRCA1/2 wild-type tumors (40.8 versus 19.5 months, HR: 0.45 [95% CI: 0.26-0.76]). ShallowHRDv2 is a performant, clinically validated, and cost-effective test for HRD detection.

Similarities and differences in gene expression profiles of BRCA1 methylated and mutated epithelial ovarian cancers

Introduction

BRCA1 methylated (BRCA1met) epithelial ovarian cancer (EOC) is a recently defined and not well-investigated subset of neoplasms. To date, no studies have focused on the transcriptional profiles of BRCA1met cases, and, as a matter of fact, we still do not know if this subset of EOCs is similar, and to what extent, to BRCA1 mutated (BRCA1mut) cases.

Methods

We compared a group of 17 BRCA1met cases against 10 BRCA1mut cases using a subset of carefully selected 17 BRCAwt EOCs as a control group.

Results

First, BRCA1met cases showed a downregulation of the relative transcript, while this association was not observed for BRCA1mut EOCs. The BRCA1met group exhibited a general upregulation of homologous recombination (HR)-related genes, as well as BRCA1mut. Overall, BRCA1met had a different gene expression profile, characterized by diffuse downregulation, whereas BRCA1mut showed a general upregulation (p < 0.0001). Both BRCA1-defective groups showed a slightly activated immune response mediated by interferon (IFN) gamma pathways.

Discussion

In conclusion, even if the expression profile of many genes related to DNA damage and repair system is shared between BRCA1mut and BRCA1met EOCs supporting that BRCA1met EOCs may benefit from PARPi therapies, our data demonstrate that BRCA1mut and BRCA1met EOCs show different expression profiles, suggesting a different mechanism of carcinogenesis that can be reflected in different responses to therapies and disease recovery.

PARP Inhibitors in Ovarian Cancer: A Review

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) have transformed the ovarian cancer (OC) treatment landscape. This narrative review provides a comprehensive overview of data for the PARPis olaparib, niraparib, and rucaparib in patients with OC and discusses their role in disease management, with a focus on the use of PARPis as maintenance therapy in the United States (US). Olaparib was the first PARPi to be approved as first-line maintenance monotherapy in the US, with maintenance niraparib subsequently approved in the first-line setting. Data also support the efficacy of rucaparib as first-line maintenance monotherapy. PARPi maintenance combination therapy (olaparib plus bevacizumab) also provides benefit in patients with newly diagnosed advanced OC whose tumors tested positive for homologous recombination deficiency (HRD). Biomarker testing is critical in the newly diagnosed setting to identify patients most likely to benefit from PARPi maintenance therapy and guide treatment decisions. Clinical trial data support the use of PARPis (olaparib, niraparib, rucaparib) as second-line or later maintenance therapy in patients with platinum-sensitive relapsed OC. Although distinct differences in tolerability profile were observed between PARPis, they were generally well tolerated, with the majority of adverse events managed by dose modification. PARPis had no detrimental effect on patients' health-related quality of life. Real-world data support the use of PARPis in OC, although some differences between PARPis are apparent. Data from trials investigating novel combination strategies, such as PARPis plus immune checkpoint inhibitors, are awaited with interest; the optimal sequencing of novel therapies in OC remains to be established.