The largest proportion of hereditary melanoma cases are due to pathogenic variants (PVs) in the CDKN2A/p16 gene, which account for 20%-40% of familial melanomas and confer up to a 30%-70% lifetime risk for melanoma in individuals with these variants. In addition, PVs in the CDKN2A gene also increase risk for pancreatic cancer (~5–24% lifetime risk). Individuals with PVs in the CDKN2A gene also tend to have an earlier onset of cancer. Despite these known risks, uptake of germline testing has been limited in the past, largely due to perceptions of limited benefit for patients. Prevention recommendations have been developed for individuals with CDKN2A PVs as well the providers who care for them. On the patient level, behavioral modifications regarding melanoma prevention such as wearing sunscreen, limiting prolonged sun exposure and practicing general sun safety can help reduce risks. Germline testing can provide motivation for some individuals to adhere to these lifestyle changes. On the provider level, pancreatic cancer surveillance for individuals with CDKN2A PVs has been increasingly endorsed by expert consensus, although the efficacy of these surveillance methods remains under study. This review summarizes the updated surveillance guidelines for individuals with CDKN2A PVs and explores the impact of genetic counseling and testing in influencing behavioral changes in these individuals.
680 Background: Somatic tumor testing may identify germline pathogenic variants (PV) associated with cancer predisposition syndromes. Labs differ whether they offer somatic only or paired germline analysis. Methods used by somatic testing labs, even those that include germline analysis, differ from designated germline labs that have optimized the identification of germline PV. Methods: Chart reviews were performed for patients who had testing through both somatic and designated germline laboratories. Cases with discrepant results in which germline PV were not detected by the somatic laboratory are summarized. Results: Nine cases with discrepant results. Five had paired germline testing and 4 somatic testing only. All 9 patients met the criteria to undergo designated germline testing, either for Lynch syndrome (3) or BRCA1/2 testing (6), based on personal and/or family history. Designated germline testing identified 4 MLH1, 1 BRCA1, 2 ATM, 1 MUTYH and 1 RAD50 PV not reported by the somatic labs’ tumor or germline analysis; 2 MLH1 PV were called variants of uncertain significance by somatic testing but classified as PV by ClinVar and designated germline labs. Three PV identified by designated germline labs are targets for PARP inhibitors and resulted in different treatment options. Three of the MLH1 PV were identified in patients meeting Lynch Syndrome test criteria while 1 was identified in a patient meeting BRCA1/2 criteria. Among the 5 other patients meeting BRCA1/2 test criteria, 3 had PV in breast cancer genes (2 ATM, 1 BRCA1) and 2 had PV in other cancer genes ( MUTYH and RAD50) not reported by the somatic labs, highlighting the importance of panel testing. Conclusions: Methods used by somatic labs, regardless of inclusion of germline analysis, are not equivalent to those of designated germline labs. Overlooked germline PV may miss identification of hereditary syndromes and targeted therapy opportunities (e.g. Anti-PD1 immunotherapy, PARP inhibitors). Patients meeting criteria for genetic evaluation should be referred for designated germline testing regardless of somatic testing outcomes.
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