Right sided colorectal cancer increases with age and screening should be tailored to reflect this: a national cancer...

In the United States, colorectal cancer (CRC) screening and surveillance is recommended until age 75. However, rates of surgery for CRC are greatest in the elderly, questioning current guidelines. Tumor sidedness is an emerging prognostic marker that may help guide screening and treatment decisions, with specific benefit evaluating CRC anatomic distribution in the elderly. Our objective was to investigate the anatomical distribution of CRC in the elderly and factors associated with right-sidedness.

The National Cancer Database (2004-2016) was used to identify elderly patients with CRC. Cases were stratified by tumor sidedness and elderly subgroups: 65-74, 75-84, and ≥ 85 years of age, and further categorized by primary site. Multivariate analysis identified factors associated with CRC right-sidedness. The outcomes were CRC sidedness in the elderly, the anatomic distribution by age group, and factors associated with right-sidedness.

There were 508,219 colorectal cancer patients aged over 65 years identified, 54% of whom had a right-sided cancer. The right-sided incidence rates by age group were 49% (65-74 years), 58.2% (75-84 years), and 65.9% (≥ 85 years) (p < 0.001). Variables associated with right-sidedness were age (OR 1.032; 95% CI 1.031-1.033; p < 0.001), female sex (OR 1.541; 95% CI 1.522-1.561; p < 0.001), Medicare (OR 1.023, 95% CI 1.003-1.043; p = 0.027), year of diagnosis ≥ 2010 (OR 1.133; 95% CI 1.119-1.147; p < 0.001), tumor size > 5 cm (OR 1.474; 95% CI 1.453-1.495; p < 0.001), pathologic stage IV (OR 1.036; 95% CI 1.012-1.060; p = 0.003).

We found higher rates of right-sided colon cancer in the 75 and above age group. This is a population who would benefit greatly from a high-quality and complete colonoscopy for early diagnosis. As screening and surveillance for this age group are not currently recommended, our findings question the lack of universal recommendation of colonoscopy in patients over 75 years old. Guidelines for CRC screening and surveillance should consider the colon cancer right-shift in the elderly population. Based on these results, we recommend thorough assessment of the proximal colon in the elderly.