Oncological benefit of primary tumor resection with high tie lymph node dissection in unresectable colorectal cancer with synchronous peritoneal metastasis: a propensity score analysis of data from a multi-institute database.

Background: Peritoneal metastasis is recognized as a predictor of poor prognosis in patients with colorectal cancer, and whether surgical intervention for peritoneal metastasis has any clinical benefit has remained controversial. The purposes of this study were to identify prognostic factors in cases of unresectable colorectal cancer with synchronous peritoneal metastasis and to clarify the impacts of primary tumor resection with high tie lymph node dissection.

Methods: A multi-institutional retrospective analysis was conducted of 579 patients who underwent resection of the primary tumor for unresectable colorectal cancer with peritoneal metastasis between 1991 and 2007. For these 579 patients, clinicopathological variables were analyzed for prognostic significance using Cox proportional hazards model and propensity score analysis to mitigate the selection bias.

Results: Multivariate analysis revealed hematogenous metastasis (p < 0.001), histology of the tumor (p = 0.006), postoperative chemotherapy (p < 0.001), and lymph node dissection (p = 0.001) as independent prognostic factors. In the propensity-matched cohort, patients treated with high tie lymph node dissection showed a significantly better overall survival than those with low tie lymph node dissection (median overall survival 13.0 vs. 11.5 months; p = 0.041).

Conclusions: It is suggested that primary tumor resection with high tie lymph node dissection favorably affects survival, even in unresectable colorectal cancer with peritoneal metastasis.