Propensity Score Analysis in Comparisons of Long-term Outcomes for Locally Advanced Colon Cancer Between Laparoscopic Colectomy and Open Colectomy

Kiichi Sugimoto, Kazuhiro Sakamoto, Yuichi Tomiki, Michitoshi Goto, Yutaka Kojima, Hiromitsu Komiyama, Makoto Takahashi, Hirohiko Kamiyama, Shun Ishiyama, Koichiro Niwa, Shingo Ito, Masaya Kawai, Shingo Kawano, Kazuhiro Takehara, Shinya Munakata, Jun Aoki, Yu Okazawa, Rina Takahashi, Kousuke Mizukoshi, Hisashi Ro, Ryosuke Ichikawa, Kazumasa Kure, Kumpei Honjo, Ryoichi Tsukamoto. Department of Coloproctological Surgery, Juntendo University Faculty of Medicine

Introduction: Laparoscopic colectomy (LAC) for colon cancer has been applied to locally advanced colon cancer. However, because there have been some biases in the indications between LAC and Open colectomy (OC) for locally advanced colon cancer, we can’t simply compare the long-term outcomes between the two procedure on non-randomized conditions. Here, we retrospectively compared the long-term outcomes between LAC and OC using propensity score adjustment.

Methods: 226 patients who underwent colectomy (LAC: 98 patients, OC: 128 patients) for curative intent at our department between 2004 and 2010 were enrolled in the present study. Propensity score analysis was used to adjust for differences in severity of clinicopathological factors between the patients who underwent LAC and OC. The estimated probability that a patient underwent LAC was modeled for potential confounders: year of surgery (-2006 / 2007-), age, location (C, A / S, RS), invasion depth (T1-3 / T4), American Society of Anesthesiologists (ASA) score (1, 2 / ≥ 3) and the diameter of primary tumor (< 50 / ≥ 50mm). The discrimination of the propensity model was assessed with calculation of the c-statistic. The propensity score was subsequently incorporated into a proportional hazards model as a covariate. The Cox proportional-hazard model was used to determine Hazard ratios and 95% confidence intervals.

Results: There was a significant difference between the LAC group and the OC group in recurrence-free survivals (LAC; Hazard ratio= 0.59, 95% CI 0.35-0.98, P=0.04). On the other hand, there was no significant difference in cancer-specific survivals between the two group (LAC; Hazard ratio= 0.63, 95% CI 0.27-1.37, P=0.25). The median propensity score was 0.31 (0.09-0.93) in the LAC group, and 0.82 (0.08-0.99) in the OC group (P<0.0001). The c-statistic was 0.85, indicating satisfactory discrimination. After propensity score matching analysis, there were no significant differences between the LAC group and the OC group in recurrence-free survivals (LAC; Hazard ratio= 0.91, 95% CI 0.41-2.01, P=0.82) and in cancer-specific survivals (LAC; Hazard ratio= 1.38, 95% CI 0.41-4.82, P=0.59). Similarly, the analysis using the propensity score inverse probability weighting (IPW) estimator showed that there were no significant differences in both RFS and CSS.

Discussion: Propensity score analysis revealed that there was no difference in both recurrence-free survivals and cancer-specific survivals between the LAC group and the OC group. Therefore, this results suggested that LAC for locally advanced colon cancer would be equivalent to OC in long-term outcomes.

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