Previous studies have reported incidence and mortality declines for colorectal cancer (CRC). We evaluated recent temporal trends of colorectal cancer in the United States for the last 4 decades. Using the Surveillance, Epidemiology, and End Results (SEER) database, we identified primary CRCs diagnosed between 1973 and 2015. Temporal changes were evaluated by 6-year time periods. Age-adjusted incidence rates and annual percentage change (APC) for CRC were calculated by site and gender. Age-standardized relative survival rates were also evaluated. We identified 878,632 CRC patients, 51% of whom were men. For both genders, the proportions of new diagnoses of right-sided colon cancer (RCC) remained relatively stable, with the APC of - 0.8 and - 0.6 for the male and the female, respectively. There was a relative increase in RCC for the younger aged group (< 49 years). In contrast, the proportions of left-sided colon cancer (LCC) and rectosigmoid-cancer (RSC) decreased significantly over time. For those aged 0-49, the age adjusted incidence rates showed a small increase (in both genders), whereas age-adjusted incidence rates declined for those aged 50-64 and > 65 (in both genders). Our study showed near significance in the decline of CRC mortality rates in this population, except the 1-year age-standardized survival of LCC and RSC, and the 5-year age-standardized RCC in females. There was a significant increase in RCC for the younger aged group (< 49 years). In contrast, the proportions of LCC and RSC decreased significantly over time.
Keywords: Age-standardized survival; Colorectal cancer; SEER database; Tumor location shift.