Fig. 1: Flow diagram of Netherlands Cancer Registry (NCR) patients.

All NCR patients with histologically proven metastatic colorectal cancer (mCRC) were assessed for eligibility. Patients were excluded if mismatch repair (MMR) status was unknown or proficient MMR (pMMR) and if patients received immunotherapy during treatment. The final population-based cohort consists of 227 patients with deficient mismatch repair (dMMR) mCRC.