Comparative effectiveness of primary tumor resection versus chemotherapy in patients with asymptomatic unresectable metastatic colorectal cancer: a retrospective cohort study using the target trial emulation framework.

Patients who undergo primary tumor resection (PTR) reportedly have significantly higher overall survival (OS) than those who do not undergo this procedure. However, this result is only evident in past retrospective studies, and clinical trial results did not show the same trend. Thus, it remains unclear whether primary tumor resection effectively increases survival in patients with metastatic colorectal cancer (mCRC) across different study designs. We compared the OS of patients with asymptomatic unresectable mCRC who underwent PTR with that of those who did not. This retrospective cohort study was designed to be a target trial emulation of a randomized controlled trial (RCT) that would have compared the effectiveness of PTR versus non-PTR in patients with asymptomatic unresectable mCRC from 2009 to 2017. A systematic review and meta-analysis were conducted to compare the efficacy of PTR and non-PTR in patients with mCRC, and corresponding results were compared. This cohort included 1,132 patients for a per-protocol analysis. The PTR group had non-significantly longer survival (adjusted hazard ratio: 0.70, 95% confidence interval: 0.62-1.01) than the non-PTR group in our cohort. A meta-analysis including five RCTs (1,016 patients) and our cohort found that the PTR group did not have a significantly lower mortality rate than the non-PTR group. The results of this cohort study and previous RCTs suggest that PTR is not associated with improved survival compared to systemic chemotherapy combined with targeted therapy among asymptomatic unresectable mCRC patients. Therefore, routine PTR is not recommended in these patients.