Data from The impact of germline alterations in appendiceal adenocarcinoma

Abstract Purpose: Over 10% of assessed patients with appendiceal adenocarcinoma (AC) have a pathogenic (P) or likely pathogenic (LP) germline variant, including genes implicated in heritable gastrointestinal cancer syndromes, such as Lynch Syndrome. We defined the clinical and molecular impact of heritable alterations in AC to evaluate the need for dedicated appendiceal screening and prevention strategies in patients with LP/P germline variants. Experimental Design: We performed an integrated germline and somatic molecular analysis for patients with confirmed AC. Patients underwent paired tumor-normal sequencing for up to 90 hereditary cancer-risk genes and 505 genes for somatic mutation profiling. We defined the co-occurrence of LP/P germline variants and second-hit pathogenic somatic alterations. The associations between germline variants and patient clinicopathologic features were also evaluated. Results: Twenty-five out of 237 patients (10.5%) carried pathogenic or likely pathogenic germline variants in cancer susceptibility genes. Clinicopathologic characteristics and AC-specific survival were similar in patients with or without germline variants. Most (92%, N=23/25) patients with germline variants demonstrated no second-hit somatic alterations, including loss of heterozygosity. Two patients with a germline APC I1307K low-penetrance founder variant exhibited secondary somatic pathogenic alterations in APC. However only one patient tumor exhibited APC-mediated WNT-signaling dysregulation; a plausible consequence of multiple somatic APC mutations with no germline variant contribution. Four patients had germline variants in PMS2 or MSH2 associated with Lynch Syndrome, yet their cancers were microsatellite-stable. Conclusions: Germline variants are likely incidental without a contributory driver role in AC. AC screening in patients with germline variants is not clearly merited.