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Prognostic Survival Associated With Left-Sided vs Right-Sided Colon Cancer: A Systematic Review and Meta-analysis

Importance Primary tumor location is emerging as an important prognostic factor owing to distinct biological features. However, the side of origin of colon cancer (CC) still does not represent a prognostic parameter when deciding for adjuvant or palliative chemotherapy. Objective To determine the prognostic role of left vs right-sidedness of primary tumor location in patients with CC. Data Sources We searched PubMed, EMBASE, The Cochrane Library, Web of Science, LILACS, CINAHL, and SCOPUS for prospective or retrospective studies reporting data on overall survival for left-sided colon cancer (LCC) compared with right-sided colon cancer (RCC). Study Selection Studies were selected if: (1) side of CC was reported among variables entered into survival analysis, (2) survival information was available (overall survival [OS] was reported in the article as hazard ratio (HR) according to multivariate analysis, (3) articles were published in the English language. Data Extraction and Synthesis Data were pooled using HRs for OS of LCC vs RCC according to fixed or random-effects models. Subgroup analysis and multivariate random-effects model meta-regression was also implemented adjusting for stage distribution, sample size, race, year of publication, type and quality of studies, and adjuvant chemotherapy. Main Outcomes and Measures HRs for OS (the primary outcome measure) were pooled to provide an aggregate value. In this analysis, all HRs with 95% CIs were pooled to obtain prognostic information on the location of the primary tumor (left vs right location site of CC) independent of other common clinicopathological covariates. Results An analysis was made from the 66 studies conducted. It included 1 437 846 patients with a median follow-up of 65 months. Left sided primary tumor location was associated with a significantly reduced risk of death (HR, 0.82; 95% CI, 0.79-0.84; P < .001) and this was independent of stage, race, adjuvant chemotherapy, year of study, number of participants, and quality of included studies. Conclusions and Relevance Based on these results, CC side should be acknowledged as a criterion for establishing prognosis in all stages of disease. It should be considered when deciding treatment intensity in metastatic settings, and should represent a stratification factor for future adjuvant studies.