Retrospective study of prognosis of patients with multiple colorectal carcinomas: synchronous versus metachronous makes the difference.

PURPOSE Little is known about difference between synchronous colorectal cancer (SCRC) and metachronous colorectal cancer (MCRC) despite the relevance for this selected patient group. The aim of this retrospective review was to analyze patients with SCRC and MCRC. METHODS All patients who underwent surgery for SCRC and MCRC between 1982 and 2019 were included in this retrospective analysis of our tertiary referral center. Clinical, histological, and molecular genetic characteristics were analyzed. The primary endpoint was cause-specific survival, evaluated by the Kaplan-Meier method. Secondary endpoints were recurrence-free survival and the identification of prognostic factors. RESULTS Overall, 3714 patients were included in this analysis. Of those, 3506 (94.4%) had a primary unifocal colorectal cancer (PCRC), 103 (2.7%) had SCRC, and 105 (2.8%) had MCRC. SCRC occurred more frequently in elderly (p=0.009) and in male patients (p=0.027). There were no differences concerning tumor stages or grading. Patients with SCRC did not show altered recurrence or survival rates, as compared to unifocal tumors. However, MCRC had a lower rate of recurrence, compared to PCRC (24% vs. 41%, p=0.002) and a lower rate of cause-specific death (13% vs. 37%, p<0.001). Five-year cause-specific survival rates were 63±1% for PCRC, 62±6% for SCRC (p=0.588), and 88±4% for MCRC (p<0.001). Multivariable analysis revealed that MCRC were an independent favorable prognostic parameter regarding case-specific survival. CONCLUSION Patients with SCRC seem to not have a worse prognosis compared to patients with PCRC. Noteworthy, patients with MCRC showed better survival rates in this retrospective analysis.