Primary tumor site is associated with oncological outcomes after surgical resection of pT2 colorectal cancer: a retrospective study with 10-year follow-up

Purpose To evaluate long-term oncologic outcomes of pT2 colorectal cancer after upfront resection, based on tumor location within the large bowel. Methods This retrospective cohort study included patients with pT2 colorectal adenocarcinoma treated with upfront surgery at a referral cancer center between 1990–2007. Outcomes included lymph node metastasis (LNM), recurrence, and disease-specific survival by tumor location. Results 567 patients with pT2 colorectal adenocarcinoma were identified: 289 (51%) in the rectum (R), 112 (20%) in the left colon (LC), and 166 (29%) in the right colon (RC). Rates of LNM were higher in the R (26%) and LC (21%) compared to the RC (11%); adjusted ORs of 2.05 (R vs RC) and 2.01 (LC vs RC). 45 patients developed recurrence (10 local, 35 distant); 36 in rectal primaries, with a median follow-up of 120 months. Five-year cumulative incidence of recurrence was 1.3% (95%CI: 0.3–4.1), 4.6% (95%CI: 1.7–9.7) and 11% (95%CI: 7.4–15) for RC, LC, and R tumors respectively ( p < 0.001), with no significant interaction with LN status ( p interaction = 0.66). No significant association was observed between LNM and recurrence (HR 1.25, 95%CI 0.63–2.46, p = 0.5). Ten-year cumulative incidence of disease-specific death for RC, LC and R tumors was 0%, 4.3% (95%CI: 1.4–9.9), and 11.0% (95%CI: 7.5–16.0), respectively, ( p < 0.001). Conclusion Compared with resected pT2 colon cancer, resected pT2 rectal cancer was associated with significantly higher rates of recurrence and death for both node-negative and node-positive disease. These findings suggest that T2N0 rectal cancer may not be uniformly low risk. Better strategies to select T2 rectal cancer patients for neoadjuvant and adjuvant treatment are needed.