Adjuvant chemotherapy with or without pelvic radiotherapy after simultaneous surgical resection of rectal cancer with liver metastases: Analysis of prognosis and patterns of recurrence

Purpose: To investigate the outcomes of adjuvant chemotherapy (CT) or chemoradiotherapy (CRT) after simultaneous surgical resection in rectal cancer patients with liver metastases (LM). Materials and Methods: One hundred and eight patients receiving total mesorectal excision for rectal cancer and surgical resection for LM were reviewed. Forty-eight patients received adjuvant CRT, and 60 were administered CT alone. Recurrence patterns and prognosis were analyzed. Disease-free survival (DFS) and overall survival (OS) rates were compared between the CRT and CT groups. The inverse probability of the treatment-weighted (IPTW) method based on the propensity score was used to adjust for selection bias between the two groups. Results: At a median follow-up period of 47.7 months, 77 (71.3%) patients had developed recurrences. The majority of recurrences (68.8%) occurred in distant organs. By contrast, the local recurrence rate was only 4.7%. Median DFS and OS were not significantly different between the CRT and CT groups. After applying the IPTW method, we observed no significant differences in terms of DFS (hazard ratio [HR], 1.347; 95% confidence interval [CI], 0.759-2.392; p = 0.309) and OS (HR, 1.413; CI, 0.752-2.653; p = 0.282). Multivariate analyses showed that unilobar distribution of LM and normal preoperative carcinoembryonic antigen level (<6 mg/mL) were significantly associated with longer DFS and OS. Conclusions: The local recurrence rate after simultaneous resection of rectal cancer with LM was relatively low. DFS and OS rates were not different between the adjuvant CRT and CT groups. Adjuvant CRT may have a limited role in this setting. Further prospective randomized studies are required to evaluate optimal adjuvant treatment in these patients.