A systematic review of population-based studies on metachronous metastases of colorectal cancer.

Abstract

The occurrence of metachronous metastases (MM) of colorectal (CRC), colon (CC), and rectal (RC) cancer of population-based studies has not been compiled in a systematic review previously. MEDLINE, Embase, and Cochrane Library were searched for primary studies of any design from inception until January 2021 and updated in August 2023 (CRD42021261648). The PRISMA guidelines were adopted, and the Newcastle-Ottawa Quality Assessment Scale used for risk of bias assessment. Outcomes on overall and organ-specific MM were extracted. A narrative analysis followed. Out of 2143 unique hits, 162 publications were read in full-text and 37 population-based cohort studies published in 1981-2022 were included. Ten studies adopted time-dependent analyses; eight were registry-based and seven had a low risk of bias. Three studies reported 5-year recurrence rate of MM overall of stages I-III; for CRC, it was 20.5%, for CC, it was 18% and 25.6%, and for RC, it was 23%. Four studies reported 5-year recurrence rate of organ-specific MM of stages I-III-for CRC, it was 2.2% and 5.5% for peritoneal metastases and 5.8% for lung metastases and for CC 4.5% for peritoneal metastases. Twenty-seven studies reported proportions of patients diagnosed with MM, but data on the length of follow-up was incomplete and varied widely. Proportions of patients with CRC stages I-III that developed MM overall was 14.4%-26.1% in 10 studies. In relation to the enrollment period, a downward trend may be discernible. Studies adopting a more appropriate analysis were highly heterogeneous, whereas uncertain data of partly inadequate studies may indicate that MM are overall declining.