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

Surveillance, Epidemiology, and End Results (SEER) public research database does not include chemotherapy data due to concerns for incomplete ascertainment. To compensate for perceived lack of data quality many researchers use SEER-Medicare linked data, limiting studies to persons over age 65. We sought to determine current SEER ascertainment of chemotherapy receipt in two relatively large SEER registries compared to patient-reported receipt and to assess patterns of under-ascertainment. In 2011-14, we surveyed patients with Stage III colorectal cancer reported to the Georgia and Metropolitan Detroit SEER registries. 1301/1909 eligible patients responded (68% response rate). Survey responses regarding treatment and sociodemographic factors were merged with SEER data. We compared patient-reported chemotherapy receipt with SEER recorded chemotherapy receipt. We estimated multivariable regression models to assess associations of under-ascertainment in SEER. Eighty-five percent of patients reported chemotherapy receipt. Among those, 10% (n = 104) were under-ascertained in SEER (coded as not receiving chemotherapy). In unadjusted analyses, under-ascertainment was more common for older patients (11.8% age 76+ vs.