Are current family-history based colorectal cancer screening guidelines adequate for early detection and potential prevention of young-onset cases?

3549 Background: Strategies to detect and prevent young-onset colorectal cancer (YOCRC, diagnosed under age 50) are critical. Established high-risk screening guidelines (SGs) aim to detect/prevent YOCRCs arising from hereditary syndromes. For non-hereditary YOCRCs, average-risk screening is being considered at an earlier age, but family history (FH)-based increased-risk screening has been poorly studied. We aimed to define the proportion of non-hereditary YOCRC with a FH, and to determine whether existing SGs could have detected/prevented these cases. Methods: 394 consecutive YOCRC patients presenting for surgical resection were reviewed for tumor MMR status, pedigree and genetic testing. Those with known/suspected hereditary syndrome (by phenotype, MMR status, and/or germline mutation) were excluded (N = 65). Pedigrees (N = 329) were analyzed for first- or second-degree relatives (FDR, SDR) with CRC and the ages of diagnosis. The gap between the recommended age for FH-based CRC screening and the age of YOCRC diagnosis was calculated. Results: 89 (27%) non-hereditary YOCRC patients had a FH of CRC. The median age of diagnosis was 45; the tumors were mostly from the distal colon (22%) and rectum (60%), and stage III (48%) and IV (27%). Twenty-one (24%) patients had 22 FDRs with CRCs diagnosed at age 64 (median); and 71 (80%) patients had 92 SDRs with CRCs diagnosed at age 65 (median). Thirteen (15%) had a FH of YOCRC. The existing SGs consider 39 patients (44%) at increased-risk, and the remaining, average-risk (Table). Screening would have begun prior to the YOCRC diagnoses in 28 (31% [or 46, 52%]) patients. But YOCRC diagnosis preceded the recommended screening age in the remaining 61(69% [or 43, 48%]) patients by a median of 5.3 [or 3.9] years (Table). Conclusions: FH is found in 27% of the non-hereditary YOCRC patients; 15% has a FH of YOCRC. In nearly half of the patients, YOCRC was diagnosed several years earlier than the recommended age for FH-based screening, even assuming perfect SG adoption and starting average risk screening at age 45. Refining existing FH-based SGs can potentially be impactful.[Table: see text]