OBJECTIVES: Although chemotherapy was proven efficacious for metastatic breast cancer (MBC) in clinical trials, lower chemotherapy rates have been observed among older patients. This may be due to greater uncertainty in the trade-off between the risks and the benefit of chemotherapy associated with older age because of the underrepresentation of older patients in cancer clinical trials. These uncertainties may cause other non-clinical factors, such as access, to matter more for older patients. We examined the effect of access to cancer care, including travel distance to the nearest oncologist practice, local area per capita number of oncologists, per capita number of hospices, and area chemotherapy rate among stage IV cancer patients across four cancers, on age-related difference in chemotherapy use for elderly MBC patients. METHODS: The retrospective cohort study used the 1992-2002 SEER-Medicare database. Chemotherapy use was defined as at least one chemotherapy-related claim within 6 months post diagnosis. We defined five age subgroups: 66-69, 70-74, 75-79, 80-84, and 85+. For each age subgroup, we used multivariate logistic regression to estimate the effect of access to cancer care on chemotherapy use controlling for covariates. RESULTS: Among 4533 elderly patients with MBC, 30.16% used chemotherapy. Chemotherapy rate decreased with age. Subgroup analysis showed that the area treatment rate was positively associated with chemotherapy use in all age groups. In addition, among patients who were 85+ years old, local area oncologist supply was negatively associated with chemotherapy use. This effect was not observed among younger age groups. CONCLUSIONS: Access to cancer care affects chemotherapy choice among older patients whose clinical evidence is unclear, which may be attributable to patient preferences and physician concerns of real benefits of chemotherapy considering older patients’ limited life expectancy and higher risk of toxicities. The more uncertain the evidence with age, the more access may affect chemotherapy choice.