In a Dutch population-based observational cohort study reported in JAMA Oncology, Rovers et al found that adjuvant systemic chemotherapy was associated with improved overall survival vs active surveillance after upfront resection of isolated synchronous colorectal peritoneal metastases.

Study Details

The study used nationwide data from the Netherlands Cancer Registry on 393 patients diagnosed between January 2005 and December 2017 who had isolated synchronous colorectal peritoneal metastases and were alive at 3 months after upfront complete cytoreductive surgery with hyperthermic intraperitoneal chemotherapy. Follow-up was conducted through January 2019. Adjuvant systemic chemotherapy was defined as systemic chemotherapy without targeted therapy starting within 3 months after surgery. Patients who received adjuvant systemic chemotherapy were matched 1:1 with patients who received active surveillance using propensity scores based on patient-, tumor-, and treatment-level covariates.

Overall Survival

Among all 393 patients, 172 had received adjuvant systemic chemotherapy. Analysis was performed in propensity score–matched groups of 142 who received adjuvant chemotherapy and 142 who received active surveillance. In the entire matched population, median follow-up was 25.9 months.

Median overall survival was 39.2 months (interquartile range [IQR] = 20.8–51.5 months) in the adjuvant chemotherapy group vs 24.8 months (IQR = 12.5–34.7 months) in the active surveillance group (adjusted hazard ratio [HR] = 0.66, P = .006). Overall survival at 1, 3, and 5 years was 92% vs 81%, 55% vs 41%, and 35% vs 22%. The survival benefit remained significant in analysis excluding all patients who died within 6 months after surgery (adjusted HR = 0.68, P = .02) and after adjustment for major postoperative morbidity (adjusted HR = 0.71, 95% confidence interval = 0.53–0.95).

The investigators concluded, “Findings of this study suggest that in patients undergoing upfront resection of isolated synchronous colorectal peritoneal metastases, adjuvant systemic chemotherapy appeared to be associated with improved overall survival. Although randomized trials are needed to address the influence of potential residual confounding and allocation bias on this association, results of this study may be used for clinical decision-making in this patient group for whom no data are available.”

Ignace H.J.T. de Hingh, PhD, of the Department of Surgery, Catharina Cancer Institute, Eindhoven, is the corresponding author for the JAMA Oncology article.

Disclosure: For full disclosures of the study authors, visit jamanetwork.com.