Karim S, et al. - Authors planned this study to explore differences in laterality based on disease characteristics and outcomes in a population-based cohort of early-stage colon cancer. In this study, there appeared no association of disease laterality with long-term Overall survival (OS) or cancer-specific survival (CSS).

Methods

• A population-based retrospective cohort study was performed of patients with early-stage colon cancer from the province of Ontario, Canada.
• Researchers linked electronic records of treatment to the Ontario Cancer Registry to identify all patients with colon cancer who underwent resection between January 1, 2002, and December 31, 2008. October 20, 2016 was the date of the final analysis.
• A 25% random sample of all patients with resected stage I to III disease were included.
• For this study, they defined right-sided colon cancer as any tumor arising in the cecum, ascending colon, hepatic flexure, or transverse colon.
• Left-sided colon cancer included tumor arising in the splenic flexure, descending colon, sigmoid colon, or rectosigmoid colon.
• They measured overall survival (OS) and cancer-specific survival (CSS) from the time of resection.

Results

• 6365 patients with early-stage colon cancer (48.7% [3098 of 6365] female) were recognized; median age was 72 years and 51.7% (3291 of 6365) had right-sided disease.
• 18.3% (1163 of 6365) indicated stage I tumor, 38.4% (2446 of 6365) stage II, and 43.3% (2756 of 6365) stage III.
• Patients with right-sided colon cancer were more frequently older (median age, 73 vs 70 years; P < .001) and female (54.4% [1790 of 3291] vs 42.6% [1308 of 3074], P < .001) and had greater comorbidity.
• As per observations, right-sided cancers, compared with left-sided disease, were more frequently T4 (19.2% [631 of 3291] vs 15.9% [490 of 3074], P < .001) and poorly differentiated (21.1% [695 of 3291] vs 9.6% [295 of 3074], P < .001) but less frequently node positive (42.0% [1383 of 3291] vs 44.7% [1373 of 3074], P = .03).
• Adjusted analyses suggested no difference in long-term survival for right-sided compared with left-sided colon cancer: the hazard ratios were 1.00 (95% CI, 0.92-1.08) for OS and 1.00 (95% CI, 0.91-1.10) for CSS.
• When the survival analyses were restricted to stage III disease, the results remained unchanged: the hazard ratios were 1.03 (95% CI, 0.93-1.14) for OS and 1.10 (95% CI, 0.97-1.24) for CSS.