IMPORTANCE Hereditary cancer syndromes infer high cancer risks and require intensive cancer surveillance, yet the prevalence and spectrum of these conditions among unselected patients with early-onset colorectal cancer (CRC) is largely undetermined. OBJECTIVE To determine the frequency and spectrum of cancer susceptibility gene mutations among patients with early-onset CRC. DESIGN, SETTING, AND PARTICIPANTS Overall, 450 patients diagnosed with colorectal cancer younger than 50 years were prospectively accrued from 51 hospitals into the Ohio Colorectal Cancer Prevention Initiative from January 1, 2013, to June 20, 2016. Mismatch repair (MMR) deficiency was determined by microsatellite instability and/or immunohistochemistry. Germline DNA was tested for mutations in 25 cancer susceptibility genes using next-generation sequencing. MAIN OUTCOMES AND MEASURES Mutation prevalence and spectrum in patients with early-onset CRC was determined. Clinical characteristics were assessed by mutation status. RESULTS In total 450 patients younger than 50 years were included in the study, and 75 gene mutations were found in 72 patients (16%). Forty-eight patients (10.7%) had MMR-deficient tumors, and 40 patients (83.3%) had at least 1 gene mutation: 37 had Lynch syndrome (13, MLH1 [including one with constitutional MLH1 methylation]; 16, MSH2; 1, MSH2/monoallelic MUTYH; 2, MSH6; 5, PMS2); 1 patient had the APC c.3920T>A, p.I1307K mutation and a PMS2 variant; 9 patients (18.8%) had double somatic MMR mutations (including 2 with germline biallelic MUTYH mutations); and 1 patient had somatic MLH1 methylation. Four hundred two patients (89.3%) had MMR-proficient tumors, and 32 patients (8%) had at least 1 gene mutation: 9 had mutations in high-penetrance CRC genes (5, APC; 1, APC/PMS2; 2, biallelic MUTYH; 1, SMAD4); 13 patients had mutations in high- or moderate-penetrance genes not traditionally associated with CRC (3, ATM; 1, ATM/CHEK2; 2, BRCA1; 4, BRCA2; 1, CDKN2A; 2, PALB2); 10 patients had mutations in low-penetrance CRC genes (3, APC c.3920T>A, p.I1307K; 7, monoallelic MUTYH). Importantly, 24 of 72 patients (33.3%) who were mutation positive did not meet established genetic testing criteria for the gene(s) in which they had a mutation. CONCLUSIONS AND RELEVANCE Of 450 patients with early-onset CRC, 72 (16%) had gene mutations. Given the high frequency and wide spectrum of mutations, genetic counseling and testing with a multigene panel could be considered for all patients with early-onset CRC.

BACKGROUND & AIMS Germline PTEN mutations cause Cowden syndrome (CS), associated with breast and thyroid cancers. Case reports found 35–85% of CS patients had gastrointestinal (GI) hamartomas. The association of benign and malignant GI neoplasias with CS remains debatable. Our goal is to describe the GI phenotype in a prospective series of PTEN mutation carriers. METHODS Patients who met relaxed International Cowden Consortium criteria (N=2548) or with ≥5 GI polyps, ≥1 of which was hyperplastic or hamartomatous (N=397) were prospectively recruited. Germline PTEN mutation/deletion analysis was performed. Of the 2945, 127 patients having clear pathogenic PTEN mutations (123/2548+4/397) were eligible for this study. EGD and colonoscopy were performed and pathology reports reviewed. Fisher’s 2-tailed exact test, unpaired t-tests, and age- and gender-adjusted SIR were calculated. RESULTS Of 127 PTEN mutation carriers, 67 underwent ≥1 endoscopy with 62 (95%) having polyps, making GI polyps the second most common feature, after macrocephaly (74.8%). Of the 65, half had hyperplastic polyps and ¼ each with hamartomatous, ganglioneuromatous or adenomatous polyps. There were one to “innumerable” polyps in the colorectum, ileum, duodenum, stomach and/or esophagus, with 24 subjects having both upper and lower GI polyps. Nine (13%) subjects had colorectal cancer, all under the age of 50. The adjusted SIR was 224.1 (95%CI 109.3–411.3, p<0.0001). Cancers were commonly associated with adenomatous and/or hyperplastic polyps. One had gastric signet ring cell carcinoma. CONCLUSIONS PTEN-associated CS should be considered a mixed polyp syndrome, with hyperplastic polyps most prevalent, and a risk of early-onset colorectal cancer. Routine colonoscopy should be considered in PTEN-associated CS especially in the context of hyperplastic and/or adenomatous polyps.

Purpose In 2009, the Evaluation of Genomic Applications in Practice and Prevention recommended that all colorectal cancers (CRCs) be screened for Lynch syndrome (LS) through microsatellite instability (MSI) or immunohistochemistry (IHC). No studies report how this process is implemented on a health system–wide basis. Methods Since 2004, Cleveland Clinic has screened CRC specimens with MSI/IHC. Between January 2004 and July 2007, MSI/IHC results went only to the colorectal surgeon (approach 1). Between August 2007 and June 2008, colorectal surgeons and a genetic counselor received the MSI/IHC results, and the counselor e-mailed the colorectal surgeon regarding appropriate patients for genetic counseling (GC) referral (approach 2). After July 2008, the colorectal surgeon and counselor received MSI/IHC results, but the counselor contacted the patient to facilitate referral (approach 3). In approaches 2 and 3, patients were presumed to have sporadic CRC if the tumor lacked MLH1 expression and was also BRAF mutated or if the patient was diagnosed at age greater than 72 years and had no cancer family history. Results Abnormal MSI/IHC results occurred in 178 (16%) of 1,108 patients. In approach 1, 21 (55%) of 38 patients with abnormal MSI/IHC were referred for GC, 12 (32%) of 38 underwent GC, and 10 (26%) of 38 underwent genetic testing (GT). In approach 2, nine (82%) of 11 patients were referred for GC, seven (64%) of 11 underwent GC, and five (45%) of 11 underwent GT. In approach 3, 56 (100%) of 56 patients were referred for GC, 40 (71%) of 56 underwent GC, and 37 (66%) of 56 underwent GT. Time from referral to GC was 10-fold quicker in approach 3 than approach 1. Conclusion Implementation of universal MSI/IHC with GC/GT, along with effective multidisciplinary communication and plans of responsibility for patient contact, resulted in increased identification of patients with LS.