Confirmatory germline testing for presumed germline pathogenic variants using tumor-only testing.

Abstract

e22524 Background: Presumed germline pathogenic variants (PGPVs) can be detected in tumor tissues using comprehensive genomic profiling. Clinicians and patients can decide whether to conduct confirmatory germline testing or not. However, the promoting and obstructive factors for confirmatory germline testing are unclear. Methods: This single institutional retrospective study aimed to identify factors related to confirmatory germline testing in patients with PGPVs. Between April 2015 and April 2019, 270 consecutive patients with cancers of unknown primary site, rare tumors, or solid tumors refractory to standard chemotherapy, who underwent tumor-only comprehensive genomic profiling were reviewed. PGPVs were proposed to be disclosed as variants to the patients by our institutional molecular tumor board. Univariate logistic regression analysis was conducted to investigate the relationship between each patient’s characteristics and confirmatory germline testing. Factors showing a statistical relationship (p < 0.10 in univariate analyses) were included in multivariate logistic regression analysis with a backward selection of variables. Statistical significance was set at p < 0.05. Results: Of the 270 patients who underwent tumor-only comprehensive genomic profiling, 77 possessed PGPVs. The most common PGPVs were TP53 (n = 56), APC (n = 9), PTEN (n = 7), RB1 (n = 6), and BRCA2 (n = 6). Among the 77 patients, only 11 (14.3%) chose to undergo confirmatory germline testing. Multivariate logistic regression analysis revealed that the person disclosing the results (experienced oncologists with knowledge of cancer genome medicine vs. others, odds ratio [OR]: 27.7, 95% confidence interval [CI]: 4.60–167) and study period (OR: 0.110, 95% CI: 0.015–0.787) were independently and significantly associated with confirmatory germline testing. Conclusions: These findings indicate that fostering genomic competency in oncologists and collaborating with genetic experts would facilitate cancer patients and their families to receive genetic medical services in the process of cancer genomic profiling.