Clinicopathological Characteristics and Outcome of Adolescent and Young Adult-Onset Microsatellite Stable Colorectal Cancer Patients.

Colorectal cancer (CRC) incidence is increasing in adults younger than 50 years. This study evaluated clinicopathological characteristics and outcome of adolescent and young adult (AYA)-onset sporadic CRC patients. Medical records of patients who were diagnosed adenocarcinoma of colon or rectum at Siriraj Hospital between 2007 and 2018 were retrospectively reviewed. The patients were classified into two groups: AYA-onset CRC (age 15-39 years) and adult-onset CRC (age >50 years). Associations between sporadic microsatellite stable (MSS) AYA-/adult-onset CRC and clinicopathological features and outcome were evaluated. A total of 203 patients were diagnosed with AYA-onset CRC with no known history of familial CRC syndromes, 119 had data on mismatch repair status; 98 confirmed MSS CRC. AYA-onset CRC patients were commonly found with left-sided rather than right-sided tumors (77.1% vs. 22%) and late stage of disease (80.7% in stage III-IV vs. 19.3% in stage I-II). Compared with adult-onset CRC (218 patients), AYA-onset MSS CRC had more patients with female gender ( = 0.038), perineural invasion ( = 0.003), and signet ring cell/mucinous histology ( = 0.132). On univariate analysis, male gender and mucinous/signet ring cell histology had worse overall survival (OS) ( = 0.004 and  = 0.072, respectively) and remained significant in multivariate analysis for signet ring cell histology ( = 0.008). There was no difference in disease-free survival and OS between both age groups. Sporadic MSS AYA-onset CRC patients were associated with female gender and aggressive pathological characteristics. However, there was no difference in survival outcome between AYA-onset and adult-onset groups.