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

• This study examined outcomes of panel testing of colorectal cancer genes in patients with colorectal cancer at 35 or younger. • The results confirmed a previous study showing a high incidence of hereditary colorectal cancer syndromes in young patients. • Disease-specific panel testing did not increase the yield of diagnostic workup over phenotype-driven testing. • Broader panels may increase the yield but also identify more uncertain variants in young patients with colorectal cancer. 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. 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. 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. 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. [ABSTRACT FROM AUTHOR]