Early-Onset Metastatic Colorectal Adenocarcinoma Incidence and Survival Among Patients Younger Than 50 Years

There is evidence of an increasing incidence of early-onset (EO) colorectal metastatic adenocarcinoma (mADC). There is no population-based study detailing the patterns over time of the epidemiologic characteristics and prognosis of EO colorectal mADC.

To describe patterns in colorectal mADC incidence and survival according to metastatic characteristics among patients younger than 50 years compared with older patients.

This population-based cohort study used data from the French Network of Cancer Registries (FRANCIM) on 37 297 individuals with a new diagnosis of invasive colorectal adenocarcinoma from January 1, 2004, to December 31, 2021. Statistical analysis was conducted from August to November 2025.

Metastatic status was categorized into nonmetastatic disease, metastatic disease, single-site metastases, multiple-site metastases, liver metastasis, peritoneal metastasis, and lung metastasis. Incidence was modeled using a flexible multivariable Poisson model to estimate annual percentage changes according to metastatic characteristics. Net survival was estimated using the Pohar Perme estimator and a flexible cumulative hazard model.

Of the 37 297 individuals with a new diagnosis of invasive colorectal adenocarcinoma (mean [SD] age, 72.0 [12.2] years; 20 692 males [55.5%]), 1558 (4.2%) received a diagnosis before 50 years of age, and 9995 (26.8%) had mADC. The incidence of single-site metastases did not increase in any age class or sex, whereas the incidence of multiple-site metastases among patients aged 15 to 39 years increased annually by 9.5% (95% CI, 2.7%-16.7%) in males and 10.3% (95% CI, 3.4%-17.6%) in females. The increase in incidence in the EO mainly concerned the peritoneum and to a lesser extent the liver. The probability of presenting with peritoneal metastasis in 2021 was 6.2-fold higher than in 2004 among males aged 15 to 39 years. Net survival of mADC improved over time, except for peritoneal metastasis, and was consistently higher among patients aged 15 to 49 years than among those aged 50 to 75 years.

In this cohort study, the incidence of EO mADC increased mainly among patients with multiple metastatic sites and those with peritoneum rather than liver or lung involvement. Net survival improved over time except for peritoneal involvement. These results suggest that intensive treatment is needed for young adults with EO mADC when the peritoneum is involved.