Prognostic Impact of R0 Resection and Targeted Therapy for Colorectal Cancer with Synchronous Peritoneal Metastasis.

BACKGROUND: The National Comprehensive Cancer Network guidelines recommend R0 resection and targeted therapy, a combination of cytotoxic and molecular targeted agents, such as bevacizumab, cetuximab, and panitumumab, for colorectal cancer with synchronous peritoneal metastasis (M1c). While these therapeutic strategies are drawing attention, their efficacy has not been fully examined.

METHODS: The study population comprised 248 consecutive M1c patients who were treated at the National Cancer Center Hospital from 1997 to 2013. Multivariate analyses were performed to evaluate relationships between overall survival and R0 resection and targeted therapy using Cox proportional hazards regression models.

RESULTS: The 3-year overall survival (3 yOS) was 19.5%, and median survival time (MST) was 16.2 months in 248 M1c patients. R0 resection was performed in 34 patients (14%), yielding a 3-year overall survival (OS) of 48.3% and median survival time (MST) of 29.9 months. Targeted therapy was performed in 54 patients (22%) at least once during the course of treatment, yielding a 3-yr OS of 38.2% and MST of 23.9 months. After adjusting for other key clinical factors, such as the number of organs involved with metastases, performance status, primary tumor site, and extent of peritoneal metastasis, both R0 resection and targeted therapy were independent factors associated with longer OS. Targeted therapy was associated with a significantly longer OS compared with multiple cytotoxic agent therapy [hazard ratio 0.65; 95% confidence interval (0.44-0.94); p = 0.02].

CONCLUSIONS: If achievable, R0 resection is a desirable therapeutic strategy for patients with M1c colorectal cancer. Moreover, targeted therapy might be the optimal chemotherapy in this patient population.