Incidence Rates, Treatment, and Survival of Rectal Cancer Among Young Patients A Nationwide Cohort Study

Background: The incidence of colorectal cancer is increasing among young adults in the United States. We aim to investigate the incidence rate, the effect of multimodal therapy, and survival outcomes of rectal cancer in patients under 45 years of age. Patients and Methods: Data on young-onset (under 45 y) rectal cancer between 2000 and 2016 was extracted from the Surveillance, Epidemiology, and End Results Registry (SEER). Results: A total of 10,375 patients with young-onset rectal cancer were identified where 54.7% were male. The median age at diagnosis was 40 +/- 5.7 years. The overall age-adjusted incidence of rectal cancer between 2000 and 2016 was 1.24 per 100,000 per year. Incidence increased with age, with the highest incidence occurring in the 40- to 44-year age group. Over the 16-year study period, rectal cancer increased by similar to 2.29%. Most tumors on presentation were moderately differentiated (30.8%) while the most common stage at presentation was stage 4 (48.3%). One- and 5-year cause-specific survival for rectal cancer was 93% and 72%, respectively. According to Cox proportional hazard models, chemotherapy was associated with increased mortality in patients with localized cancer [hazard ratio (HR)=2.88, 95% confidence interval (CI): 2.04-4.08, P<0.001], did not significantly improve mortality outcomes in patients with regional cancer (HR=0.89, 95% CI: 0.70-1.04, P=0.116), but reduced mortality in patients with distant cancer (HR=0.62, 95% CI: 0.56-0.70, P<0.001), though this effect was largely seen in patients 35 years and older. Surgery was associated with improved survival across all cancer stages. Conclusions: The incidence of regional and distant rectal cancer is increasing in young patients. While patient age is an important prognostic indicator of survival, chemotherapy does not appear to improve survival in younger patients with localized and regional disease.