The Value of (Sub) Specialization: Evidence from Oncology

Abstract

Specialization enhances professional productivity, but its benefits depend on access to the relevant expertise. In oncology, subspecialization—the narrowing of clinical focus within cancer care—has become increasingly common, yet its effects on patient outcomes remain poorly understood. This paper estimates the causal impact of access to subspecialized oncologists on treatment and survival using a differential distance instrument based on Medicare beneficiaries’ proximity to subspecialists. Analyzing 6.1 million six-month chemotherapy episodes, we find that access to a relevant subspecialist reduces three-year mortality by 8.6% and episode spending by 3.5%. Potential mechanisms of reduced mortality are greater enrollment in disease-specific clinical trials and increased use of newer therapies. We find no evidence of increased care fragmentation and only modest indications of more intensive treatment near the end of life. Importantly, there are no mortality differences following initial oncology consultations, suggesting that survival benefits arise from differences in chemotherapy delivery rather than selective treatment of healthier patients. Our findings highlight the value of deep clinical expertise and raise important concerns about geographic disparities in access to subspecialized care.