Impact of Primary Tumor Resection on Mortality in Patients with Stage IV Colorectal Cancer with Unresectable Metastases: A Multicenter Retrospective Cohort Study

Background Primary tumor resection (PTR) before commencing systemic chemotherapy in patients with stage IV colorectal cancer and unresectable metastases (mCRC) remains controversial. This study aimed to assess whether PTR before systemic chemotherapy is associated with mortality in mCRC patients, after adjusting for confounding factors, such as the severity of the primary tumor and metastatic lesions. Methods We analyzed hospital-based cancer registries from nine designated cancer hospitals in Fukushima Prefecture, Japan. Patients were divided into two groups (PTR and non-PTR), based on whether PTR was performed as initial therapy for mCRC or not. The primary outcome was all-cause mortality. Kaplan–Meier survival analysis was performed, and survival estimates were compared using the log-rank test. Adjusted hazard ratios were calculated using Cox regression to adjust for confounding factors. All tests were two-sided; P -values