Right colon cancer: Left behind.

Introduction: Prognosis of colon cancer (CC) has steadily improved during the past three decades. This trend, however, may vary according to proximal (right) or distal (left) tumor location. We studied if improvement in survival was greater for left than for right CC.
Methods: We included all CC recorded at the Geneva population-based registry between 1980 and 2006. We compared patients, tumor and treatment characteristics between left and right CC by logistic regression and compared CC specific survival by Cox models taking into account putative confounders. We also compared changes in survival between CC location in early and late years of observation.
Results: Among the 3396 CC patients, 1334 (39%) had right-sided and 2062 (61%) left-sided tumors. In the early 1980s, 5-year specific survival was identical for right and left CCs (49% vs. 48%). During the study period, a dramatic improvement in survival was observed for patients with left-sided cancers (Hazard ratio [HR]: 0.42, 95% confidence interval [CI]: 0.29-0.62, p < 0.001) but not for right CC patients (HR: 0.76, 95% CI: 0.50-1.14, p = 0.69). As a consequence, patients with distal CC have a better outcome than patients with proximal CC (HR for left vs. right CC: 0.81, 95% CI: 0.72-0.90, p < 0.001).
Conclusion: Our data indicate that, contrary to left CC, survival of patients with right CC did not improve since 1980. Of all colon cancer patients, those with right-sided lesions have by far the worse prognosis. Change of strategic management in this subgroup is warranted.
(Copyright © 2016 Elsevier Ltd. All rights reserved.)