The accuracy of chemotherapy ascertainment among colorectal cancer patients in the surveillance, epidemiology, and end results registry program.

We found a 10% rate of under-ascertainment of adjuvant chemotherapy for resected, stage III colorectal cancer in two SEER registries. Chemotherapy under-ascertainment did not disproportionately affect any patient subgroups. Use of SEER data from select registries is an important resource for researchers investigating contemporary chemotherapy receipt and outcomes.