Background The incidence of colorectal cancer (CRC) in patients under 50 years of age, i.e., early-onset CRC, has increased in the past two decades. Colorectal peritoneal metastases (CPM) will develop in 10–30% of CRC patients. CPM traditionally had a dismal prognosis, but surgery and novel systemic treatments appear to increase survival. Determining potential age-associated risk and prognostic factors is optimized when analyses use standardized age groupings.
We performed a review of early-onset CPM studies and compared variables used, e.g., age stratification and definitions of synchronous and metachronous CPM. We included studies published in PubMed up to November 2022 if results were stratified by age.
Of 114 screened publications in English, only 10 retrospective studies met inclusion criteria. Incidence of CPM was higher in younger CRC patients (e.g. 23% vs. 2% for <25 vs. ≥25 years, P < 0.0001; and 57% vs. 39% vs. 4% for <20 vs. 20–25 vs. >25 years, P < 0.001); two studies reported higher proportion of younger African American CPM patients (e.g. 16% vs. 6% for <50 vs. ≥50 years). Studies used seven different age-stratification methods, presenting comparison challenges.
Studies showed a higher proportion of CPM in younger patients, but directly comparing results was not possible due to inconsistent reporting. To better