Mutation Landscape of Homologous Recombination Repair Genes in Epithelial Ovarian Cancer in China and Its Relationship With Clinicopathlological Characteristics

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.

Germline Mutational Landscape and Novel Targetable RAD51D Variant in Chinese Patients With Ovarian Cancer

PURPOSE

Genetic variants of ovarian cancer (OV) show ethnic differences, but data from the Chinese population are still insufficient. Here, we elucidate the inheritance landscape in Chinese patients with OV and examine the functional implications of a Chinese-enriched RAD51D variant.

METHODS

Between 2015 and 2018, 373 consecutive patients with OV were prospectively enrolled. Variants of BRCA1/2, other homologous recombination repair (HRR) genes, and DNA mismatch repair (MMR) genes were analyzed using next-generation sequencing. An enriched RAD51D variant was identified, and its functional effects were examined using Cell Counting Kit-8, colony formation, transwell migration, and drug sensitivity assays.

RESULTS

Overall, 31.1% (116/373) of patients had at least one pathogenic or likely pathogenic germline variant. BRCA1 and BRCA2 accounted for 16.09% and 5.36%, respectively, with one patient having both variants. In addition, 32 (8.58%) patients carried other HRR gene variants, whereas three (0.8%) patients had MMR gene variants. The RAD51D variant ranked third (8/373, 2.1%), and its rate was much higher than that in other populations. Remarkably, all eight patients harbored the RAD51D K91fs variant (c.270_271dup, p.Lys91Ilefs*13) and demonstrated satisfactory platinum response and favorable prognosis. This variant confers enhanced sensitivity to poly (ADP-ribose) polymerase inhibitors in OV cells. However, the effects on platinum sensitivity were inconsistent across different cell lines. Against the background of the TP53 variant, RAD51D K91fs variant showed increased sensitivity to cisplatin.

CONCLUSION

Our study revealed the inheritance landscape of OV and identified an enriched RAD51D variant in Chinese patients with OV. This can serve as an important reference for OV management and a potential therapeutic target.

Clinical characteristics and survival analysis of Chinese ovarian cancer patients with RAD51D germline mutations

OBJECTIVES

We aimed to describe the behavior among Chinese ovarian cancer patients with RAD51D germline mutations at our institution.

METHODS

Next-generation sequencing (NGS) was conducted for the entire coding regions and exon/intron boundaries of the RAD51D genes in 781 Chinese ovarian cancer patients treated at our institution from January 1, 2015 to August 1, 2021. Clinicopathological characteristics, treatment modalities, and outcomes were assessed for ovarian cancer patients with RAD51D germline mutations.

RESULTS

RAD51D germline pathogenic mutations were detected in 1.7% (13/781) of patients in this cohort. RAD51D c. 270_271dup (p. Lys91fs) mutation was the most common mutation which was found in 7 patients (7/13, 53.1%). Patients median age at diagnosis was 58 years (range: 45-69 years). 46.2% (6/13) of them were diagnosed after 60 years. Only 1 patient (1/13, 7.7%) had a family history of ovarian or breast cancer. And 1 patient (1/13, 7.7%) had a personal history of breast cancer. The FIGO 2014 distribution by stage was: stage II in 1 patient (7.7%), stage III in 9 patients (69.2%) and stage IV in 3 patient (23.1%). 92.3% (12/13) patients had high-grade serous carcinoma. 2 patients (2/13, 15.4%) had a primary peritoneal cancer. The majority of patients in the entire cohort were reported to be platinum sensitive (92.3%, 12/13) with a platinum-free interval (PFI) of > 6 months. For patients who received PARPis for 2nd line maintenance treatment (n = 5), 2 patients discontinued PARPis treatment after 33.5 and 8.1 months of duration. Other 3 patients are still on therapy with a duration of 2.4, 13.8 and 30.1 months at the date of data cutoff. 1 patient received PARPi as salvage treatment with a duration of only 1.2 months. Nine patients (9/13, 69.2%) relapsed during follow up and all of them relapsed within 2 years after diagnosis, among which 88.9% (8/9) were classified as platinum-sensitive recurrence (PSR), and only 1 patient was classified as platinum-resistant recurrence (PRR). Median PFS for the entire cohort was 17.3 months. Median PFS for the PSR subgroup was 15.9 months. 2 patients died during follow-up. The OS of these 2 patients was 17.2 and 39.6 months. The 5-year OS rate was 67.5%.

CONCLUSIONS

RAD51D germline mutations are more frequent in Chinese ovarian cancer patients than other population. Few patients have a family history of ovarian or breast cancer, and personal history of breast cancer. Most patients are diagnosed after 50 years. The sensitivity to PARP inhibitors of patients with RAD51D germline mutations need a further analysis.

Targeting Homologous Recombination Deficiency in Ovarian Cancer with PARP Inhibitors: Synthetic Lethal Strategies That Impact Overall Survival

The advent of molecular targeted therapies has made a significant impact on survival of women with ovarian cancer who have defects in homologous recombination repair (HRR). High-grade serous ovarian cancer (HGSOC) is the most common histological subtype of ovarian cancer, with over 50% displaying defective HRR. Poly ADP ribose polymerases (PARPs) are a family of enzymes that catalyse the transfer of ADP-ribose to target proteins, functioning in fundamental cellular processes including transcription, chromatin remodelling and DNA repair. In cells with deficient HRR, PARP inhibitors (PARPis) cause synthetic lethality leading to cell death. Despite the major advances that PARPis have heralded for women with ovarian cancer, questions and challenges remain, including: can the benefits of PARPis be brought to a wider range of women with ovarian cancer; can other drugs in clinical use function in a similar way or with greater efficacy than currently clinically approved PARPis; what can we learn from long-term responders to PARPis; can PARPis sensitise ovarian cancer cells to immunotherapy; and can synthetic lethal strategies be employed more broadly to develop new therapies for women with ovarian cancer. We examine these, and other, questions with focus on improving outcomes for women with ovarian cancer.