Outcomes of disease-specific next-generation sequencing gene panel testing in adolescents and young adults with colorectal cancer

Purpose: Adolescents and young adults with colorectal cancer (CRC) have attracted recent attention, with a hereditary syndrome identified in one-third of patients diagnosed ≤ 35. We aimed to study this population to determine if a CRC-specific gene panel increased the yield of testing. Methods: Patients with CRC ≤ 35 evaluated from 05/2014–11/2017 were identified from the genetic counseling database. Records were reviewed for personal/family history and genetic counseling outcomes. Results: One hundred forty-three patients with CRC ≤ 35 were included. One hundred four (72.7%) underwent CRC panel testing. Thirty-nine (27.2%) had syndrome-directed testing, declined, or were lost to follow-up. Forty-two patients had a genetic syndrome (29.4%). Twenty-four of the 42 hereditary patients (57.1%) were identified via syndrome-directed testing. Mutations identified via panel testing were consistent with patient personal/family history. Thirty-three patients had at least one variant of uncertain significance. Conclusion: Hereditary syndromes were identified in 29.4% of patients. Panel testing in patients without a phenotype did not increase diagnostic yield, but identified variants in one-third. Disease-specific panel testing is of low yield in young patients without a suggestive personal/family history. Testing broader panels may increase the yield of mutation pick-up in this population, although at the expense of identifying variants.