To explore the correlation between age and treatment strategies and prognosis of metastatic colorectal cancer.

A total of 43 977 patients with mCRC were identified from the National Cancer Database (NCDB) spanning ten years (2004~2014). Patients were classified into three age groups: 18~49, 50~75, and >75 years old. Percentages of patients within each treatment category were described, including primary tumor resection (PTR) only, chemotherapy only, and PTR plus chemotherapy. After adjusting for demographic and clinical factors, restricted mean survival time (RMST) was calculated and compared between different age and treatment groups.

The majority (61.8%) of patients in the 18~49 age group received PTR plus chemotherapy; about half (53.3%) of the patients in the 50~75 age group and about one third (34.7%) in the >75 age group received PTR plus chemotherapy. There was a decreasing trend in the PTR plus chemotherapy group and an increasing trend in the chemotherapy only group for mCRC patients over the study time period in all age groups. PTR plus chemotherapy demonstrated the most favorable survival rate in all age groups compared to other treatments. Chemotherapy only was associated with significantly higher survival time compared to PTR, except for patients in the ages 18~49 group. Among patients who had PTR plus chemotherapy treatment, peri-operative chemotherapy was associated with the longest survival rate among patients in the ages 18~49 and 50~75 groups, but not in the >75 group, compared to other treatments.

A decreasing trend of PTR plus chemotherapy was observed among mCRC patients between 2004~2014, though it showed the most survival benefit in all age groups. The benefits of specific multimodality treatment vary by age group.