Impact of treatment modality on clinical outcome in metastatic colorectal cancer patients stratified by metastatic sites

Objectives: To investigate the impact of location of metastases, and therapeutic modality on clinical outcomes in patients with metastatic colorectal cancer (CRC). Methods: Data for metastatic CRC patients were sourced from the Surveillance, Epidemiology, and End Results (SEER) database (SEER ID: 15309-Nov2017). Patients were classified as follows: Group 1 patients had only liver metastasis; Group 2 patients had liver and lung metastasis; Group 3 patients had more than two metastasis sites. Patients were treated with surgery alone, radiation alone, or surgery plus radiation. The main study outcomes were (1) cancer-specific mortality and (2) survival benefit associated with treatment modality. Results: A total number of 15,510 patients were included in this study. In Groups 1 and 2, patients treated with surgery plus radiation had a higher cumulative survival compared to other treatment groups (p-value <.001). Group 3 patients showed no significant difference in cumulative survival between the different treatment modalities (p-value = .218). Group 1 patients who received surgery plus radiation had a significantly lower risk of mortality compared to the other treatment groups (p-value <.001), and Group 2 patients who either received radiation treatment alone or surgery plus radiation had a significantly lower risk for mortality than patients who received other treatment modalities (p-value <.001). Multivariate analysis adjusting for known prognostic factors such as tumor sidedness and race did not alter the observed risk conferred by metastasis sites and treatment modalities. Conclusion: Stratification by metastases sites, and by treatment modality can help multidisciplinary teams to reach a treatment consensus for metastatic CRC.