Homologous Recombination Inquiry Through Ovarian Malignancy Investigations: JGOG3025 study

Molecular classification of ovarian high-grade serous/endometrioid carcinomas through multi-omics analysis: JGOG3025-TR2 study

BACKGROUND

Considerable interobserver variability exists in diagnosis of ovarian high-grade endometrioid carcinoma (HGEC) and high-grade serous carcinoma (HGSC) due to histopathological similarities. While homologous recombination deficiency (HRD) correlates with drug sensitivity in HGSC, the molecular features of HGEC are unclear.

METHODS

Fresh-frozen samples from 15 ovarian HGECs and 274 ovarian HGSCs in the JGOG-TR2 cohort were submitted to targeted DNA sequencing, RNA sequencing, DNA methylation array, and SNP array. We additionally analyzed 555 ovarian HGSCs from TCGA-OV and 287 endometrial high-grade carcinomas from TCGA-UCEC.

RESULTS

Unsupervised clustering using copy number signatures identified four distinct tumor groups (C1, C2, C3 and C4). C1 (n = 41) showed CCNE1 amplification and poor survival. C2 (n = 160) and C3 (n = 59) showed high BRCA1/2 alteration frequency with low and moderate ploidy, respectively. C4 (n = 22) was characterized by favorable outcome, higher HGEC proportion, no BRCA1/2 alteration or CCNE1 amplification, and low levels of HRD score, ploidy, intra-tumoral heterogeneity, cell proliferation rate, and WT1 gene expression. Notably, C4 exhibited a normal endometrium-like DNA methylation profile, thus, defined as "HGEC-type" tumors, which were also identified in TCGA-OV and TCGA-UCEC.

CONCLUSIONS

Ovarian "HGEC-type" tumors present a non-HRD status, favorable prognosis, and endometrial differentiation, possibly constituting a subset of clinically diagnosed HGSCs.

Clinical and molecular biomarkers predicting response to PARP inhibitors in ovarian cancer

OBJECTIVE

To determine the useful biomarker for predicting the effects of poly-(ADP ribose)-polymerase (PARP) inhibitors in Japanese patients with ovarian cancer.

METHODS

We collected clinical information and performed molecular biological analysis on 42 patients with ovarian, fallopian tube, and primary peritoneal carcinomas who received PARP inhibitors.

RESULTS

Among the analyzed patients with ovarian cancer, 23.8% had germline BRCA mutation (gBRCAm), 42.9% had homologous recombination repair-related gene mutation (HRRm), and 61.1% had a genomic instability score (GIS) of ≥42. Patients with HRRm had a significantly longer progression-free survival (PFS) than those without HRRm (median PFS 35.6 vs. 7.9 months; p=0.009), with a particularly marked increase in PFS in patients with gBRCAm (median PFS 42.3 months). Similarly, among patients with recurrent ovarian cancer, those with HRRm had a longer PFS than those without HRRm (median PFS 42.3 vs. 7.7 months; p=0.040). Multivariate Cox proportional hazards regression analysis found that performance status and gBRCAm status were independent factors associated with prolonged PFS with PARP inhibitors. In recurrent ovarian cancer, multivariate regression analysis identified platinum-free interval (PFI) in addition to performance status as a significant predictor of PFS. On the contrary, no significant association was observed between PFS and a GIS of ≥42 used in clinical practice.

CONCLUSION

We found that HRRm can be a useful biomarker for predicting the effects of PARP inhibitors in treating ovarian cancer and that the PFI can also be useful in recurrent ovarian cancer.

Genomic Landscape of Endometrial, Ovarian, and Cervical Cancers in Japan from the Database in the Center for Cancer Genomics and Advanced Therapeutics

This study aimed to comprehensively clarify the genomic landscape and its association with tumor mutational burden-high (TMB-H, ≥10 mut/Mb) and microsatellite instability-high (MSI-H) in endometrial, cervical, and ovarian cancers. We obtained genomic datasets of a comprehensive genomic profiling test, FoundationOne® CDx, with clinical information using the "Center for Cancer Genomics and Advanced Therapeutics" (C-CAT) database in Japan. Patients can undergo the tests only after standardized treatments under universal health insurance coverage. Endometrial cancers were characterized by a high frequency of TMB-H and MSI-H, especially in endometrioid carcinomas. The lower ratio of POLE exonuclease mutations and the higher ratio of TP53 mutations compared to previous reports suggested the prognostic effects of the molecular subtypes. Among the 839 cervical cancer samples, frequent mutations of KRAS, TP53, PIK3CA, STK11, CDKN2A, and ERBB2 were observed in adenocarcinomas, whereas the ratio of TMB-H was significantly higher in squamous cell carcinomas. Among the 1606 ovarian cancer samples, genomic profiling of serous, clear cell, endometrioid, and mucinous carcinomas was characterized. Pathogenic mutations in the POLE exonuclease domain were associated with high TMB, and the mutation ratio was low in both cervical and ovarian cancers. The C-CAT database is useful for determining the mutational landscape of each cancer type and histological subtype. As the dataset is exclusively collected from patients after the standardized treatments, the information on "druggable" alterations highlights the unmet needs for drug development in major gynecological cancers.