Understanding visiting oncologists and chemotherapy use among elderly stage II colon cancer patients

Objectives: Although adjuvant chemotherapy is not recommended for treating stage II colon cancer patients, approximately 30% receive it. We examined the determinants of post-surgical oncologist visits and subsequent chemotherapy among elderly stage II colon cancer patients.

Methods: 5,379 stage II colon cancer patients aged 67-79 from SEER-Medicare data were studied. Oncologist visits and chemotherapy were assessed based on chemotherapy administration and drug information on the claims. The effects of relevant patient, health service and physician characteristics on these outcomes were assessed by generalized linear mixed models with hospital and surgeon/oncologist as the cluster factors.

Results: 77% of patients visited an oncologist after surgery; 39% received chemotherapy. Blacks, older patients, and those with state medical subsidy, living alone, or living in rural areas were less likely to visit an oncologist. Surgery performed in teaching and large-volume hospitals was related to lower rates of oncologist visits. However, among patients who visited an oncologist, chemotherapy use was the same among blacks and whites, although age and state subsidy effects persisted. Patients with poorly differentiated tumor, bowel obstruction or perforation, and tumor invaded neighboring tissues or organs (Stage IIb) had higher rates of chemotherapy, while hospital and surgeon factors were not related to chemotherapy. Those who visited an oncologist who prescribed chemotherapy more frequently were almost 3 times as likely to receive chemotherapy.

Conclusion: Visiting an oncologist was related to the personal and health care access factors, while the chemotherapy was related to clinical factors and physician experience.