Prognostic relevance of sidedness in older patients with colon cancer: A review and pooled analysis of 227,218 patients

Age is a major risk factor for sporadic colon cancer (CC). In the general population, the side of the tumor (right versus left) shows a possible significant prognostic effect, with right tumors displaying the worst outcome due to biological differences. However, little is known about the role of sidedness in the older population. We conducted a pooled analysis of observational and prospective studies to confirm or reject the hypothesis that side is a prognostic variable, even in older patients with CC. Using the terms ("colorectal" or "colon") and ("cancer" or "carcinoma") and ("elderly" or "older" or "65 years" or "70 years" or "75 years") and ("side" or "site" or "right" or "left"), we searched PubMed, Embase, and the Cochrane Library through January 2023. We selected studies in the English language to compare the prognosis of left versus right CC in older patients (with a lower age limit of 65 years). The primary endpoint was overall survival (OS). Hazard ratios (HRs) for OS with relative 95% confidence intervals (CIs) were extracted from each study. Summary HRs were calculated using random- or fixed-effects models, depending on the heterogeneity of the included studies. The review process led to the inclusion of 13 articles. The studies reported the OS data for a total of 227,218 patients with CC. The CC side was not independently associated with mortality risk in older CC patients (HR 0.97; 95% CI 0.9-1.04; p = 0.34). High heterogeneity was observed in the main analysis (P < 0.01; I2 = 85%). In conclusion, our analysis shows that the tumor being on the left or right side in older patients with CC has no significant role in the risk of overall death. These data support the use of other parameters, such as stage, biology, comorbidities, and life expectancy, to decide on treatment and the prolongation of screenings until a patient's latest years.