Age-adjusted incidence rates of synchronous liver metastases for stage IV colorectal cancer compared by sex, race, and age group

Background: Reports on age-adjusted incidence rates of synchronous colorectal liver metastases (CRLM) among patients with stage IV colorectal cancer (CRC) are uncommon. This study presents in detail differences in CRLM incidence rates by sex, race, and age group. Methods: Incidence rates were obtained for adults diagnosed with Stage IV CRC in the years 2010-2015 using SEER. The ratio of CRLM incidence to stage IV CRC incidence was used to calculate the rate ratio. Results: Average age-adjusted CRLM incidence rate was 7.09 per 100,000 (95% CI, 6.93-7.26). CRLM incidence was higher at 8.68 (95% CI, 8.35-9.03) for males compared with 5.77 (95% CI, 5.64-5.90) for females. Highest incidence rate of 11.50 (95% CI, 10.43-11.76) was observed among Blacks. By age group the highest CRLM incidence was 24.42 (95% CI, 23.13-25.71) among adults age >75. The average rate ratio of CRLM to CRC incidence rate was 0.72 (95% CI, 0.71-0.73). Conclusion: Age-adjusted incidence rates of synchronous CRLM are higher for men, Blacks, and older patients. The risk ratio indicates that 72% of stage IV CRC cases are at risk of synchronous CRLM, although CRLM risk appears to decline with age.