Additional germline findings from a tumor profiling program

Background: Matched tumor-normal sequencing, applied in precision cancer medicine, can identify unidentified germline Medically Actionable Variants (gMAVS) in cancer predisposition genes. We report patient preferences for the return of additional germline results, and describe various gMAV scenarios delivered through a clinical genetics service. Methods: Tumor profiling was offered to 1960 advanced cancer patients, of which 1556 underwent tumor-normal sequencing with multigene hotspot panels containing 20 cancer predisposition genes. All patients were provided with an IRB-approved consent for return of additional gMAVs. Results: Of the whole cohort 94% of patients consented to be informed of additional germline results and 5% declined, with no statistically significant differences based on age, sex, race or prior genetic testing. Eight patients were found to have gMAVs in a cancer predisposition gene. Five had previously unidentified gMAVs: three in TP53 (only one fulfilled Chompret's Revised criteria for Li-Fraumeni Syndrome), one in SMARCB1 in the absence of schwannomatosis features and one a TP53 variant at low allele frequency suggesting an acquired event in blood. Conclusion: Interest in germline findings is high among patients who undergo tumor profiling. Disclosure of previously unidentified gMAVs present multiple challenges, thus supporting the involvement of a clinical genetics service in all tumor profiling programs.