Assessing actionability and incidental findings of germline variants in two precision oncology trials

High-throughput sequencing techniques have revolutionized oncology. Paired germline-tumor DNA analysis has emerged as a comprehensive strategy to uncover actionable alterations in advanced cancer patients (ACP) enrolled in precision oncology trials. However, challenges persist in variant interpretation and managing incidental germline findings.

We conducted a study involving 288 ACP from MOSCATO (NCT01566019) and MATCHR (NCT02517892) trials to assess germline variants impacting cancer-related genes. Germline DNA sequencing was performed using a panel of 250 cancer-related genes, and the results were discussed during tumor molecular board sessions.

Germline pathogenic variants (PV) were classified according to the ESCAT classification. Lung cancer (36.8 %), followed by prostate (18.4 %) and breast cancer (17.7 %), comprised the most prevalent tumor types. PVs were found in 12.5 % of patients. Most PVs were classified as ESCAT X (63.9 %), highlighting limited therapeutic actionability. Notably,2 % of patients had actionable variants (ESCAT I-A/II-A). Incidental findings included 7.3 % of patients with PVs in cancer-predisposition genes, with 2.4 % having very high-risk potential, necessitating mandatory oncogenetic counseling. Nearly one in five patients (21.9 %) had at least one VUS.

Our study underscores the significance of germline sequencing in identifying actionable alterations and the need for improved variant interpretation as well as pretest counseling plans in precision oncology trials.