Influence of private practice setting and physician characteristics on the use of breast cancer adjuvant chemotherapy for elderly women

BACKGROUND: Although >70% of younger women with nonmetastatic breast cancer (BC) received adjuvant chemotherapy, only approximately 15% to 20% of elderly women with BC received chemotherapy. The decision to treat may be associated with nonmedical factors, such as patient, physician, or practice characteristics. In the current study, the association between oncologist characteristics and the receipt of chemotherapy in elderly women with BC was evaluated. METHODS: Women aged >65 years who were diagnosed with American Joint Committee on Cancer stages I to III BC between 1991 and 2002 were identified in the Surveillance, Epidemiology, and End Results-Medicare database. The Physician Unique Identification Number was linked to the American Medical Association Masterfile to obtain information on oncologists. Investigated was the association between demographic, tumor, and oncologist-related factors and the receipt of chemotherapy, using Generalized Estimating Equations to control for clustering. Patients were defined as low risk (estrogen/progesterone receptor positive, stage I/II disease) and high risk (estrogen/progesterone receptor-negative, stage II/III disease). RESULTS: Of 42,544 women identified, 8714 (20%) were treated with adjuvant chemotherapy. In a hierarchical analysis, women who underwent chemotherapy were more likely be treated by oncologists primarily employed in a private practice (odds ratio [OR], 1.40; 95% confidence interval [95% CI], 1.23-1.59) and who graduated after 1975 (OR, 1.12; 95% CI, 1.01-1.26) and were less likely to have an oncologist trained in the United States (OR, 0.83; 95% CI, 0.74-0.93). The association between a private practice setting and the receipt of chemotherapy was found to be similar for patients at high risk (OR, 1.55) and low risk CONCLUSIONS: Elderly women with BC treated by oncologists who were employed in a private practice were more likely to receive chemotherapy. Efforts to determine whether these associations reflected experience, practice setting, insurance type, or other economic incentives are warranted.