Background: Colorectal cancer (CRC) incidence is increasing in patients younger than 50 years old. Currently, there are discordant recommendations regarding CRC screening: while the American Cancer Society favors to start at age 45, the National Comprehensive Cancer Network and the US Preventive Task Force suggest starting at age 50. This study is aimed to compare the incidence, clinical characteristics and survival of patients diagnosed with standard-onset CRC (SO) versus early-onset colorectal cancer by age-groups. Methods: Patients diagnosed with CRC at ages older than 35 were identified using the SEER registry and categorized into four groups based on age at diagnosis. EO1 (35-39), EO2 (40-44), EO3 (45-49) and SO (>50) years, respectively. Incidence, clinical features and survival were compared among groups. Results: 178 678 patients were identified. 9.2% were diagnosed before 50 years. Of these, 1.4%, 2.8% and 5.1% were EO1, EO2 and EO3; respectively. Patients with early-onset CRC (EO) had higher frequency of Hispanics (13.9% vs. 8.4%, p<0.01), stage IV (24.8% vs. 17.3%, p<0.01), left-sided tumors (74.1% vs. 56.9%, p<0.01) and better survival compared to SO. Among EO groups, the frequency of poor/anaplastic grade was inversely proportional to age; stage IV was similar between EO2 and EO3 and lower in EO1. Black race, grade and stage were predictors of mortality for all EO groups; laterality was a mortality predictor in EO2 and EO3. Conclusions: EO-CRC and SO-CRC have different pathological features that should be considered for CRC screening. Higher rates of stage IV disease are encountered in patients between 40-49 years old; hence early screening should be considered. Given higher rates of left-sided tumors, sigmoidoscopy might be an adequate tool for most patients with EO-CRC.

p* comparison between EO groups