The influence of tumour site on prognosis in metastatic colorectal carcinomas with primary tumour resection.

PURPOSE: The aim of our study was to compare the characteristics and prognosis between right- and left-sided metastatic colorectal carcinomas.
METHODS: Data from 937 patients with stage IV colorectal carcinomas (synchronous distant metastasis) who had a resection of the primary tumour between 1985 and 2014 were analysed. Carcinomas in the caecum to transverse colon were defined as right-sided (n = 250; 26.7%). They were compared to tumours located from the splenic flexure to the rectum categorised as left-sided (n = 687; 73.3%).
RESULTS: In right-sided carcinomas, we observed significantly more female patients (50.8 vs 36.2%; p < 0.001), more unfavourable histological types (24.0 vs 8.6%; p < 0.001), more M1c carcinomas (metastases to the peritoneum ± others; 32.0 vs 14.4%; p < 0.001) and more emergencies (11.6 vs 7.1%; p = 0.029), while multimodal treatment was utilised in fewer patients (51.6 vs 63.8%; p = 0.001) and curative resections were less frequently (24.1 vs 35.4%; p = 0.002). Prognosis was significantly worse in patients with right-sided carcinomas (2-year-survival 27.2 vs 44.6%, p < 0.01). This difference was more pronounced after R2 resection (15.3 vs 29.7%; p < 0.001), than after macroscopic curative resection (2-year-survival 63.9 vs 71.9%; p = 0.106). In multivariate Cox regression analysis, tumour site was found to be an independent prognostic factor for overall survival (HR 1.2; 95% CI 1.0-1.5; p = 0.012). During the three 10-year periods, the prognosis improved equally in patients with right- and left-sided carcinomas, while the differences in survival remained identical.
CONCLUSIONS: In a surgical patient cohort undergoing primary tumour resection, significant differences in prognosis were observed between patients with metastatic right- and left-sided colorectal carcinomas.