Fahui Wang

Prior research has defined cancer service areas (CSAs) anchored by major cancer centers in the U.S., such as members of the Association of American Cancer Institutes (AACI). Those CSAs have discrete boundaries and may not capture the increasingly interwoven cancer care markets. This is the first attempt to delineate possible overlapping CSAs. Specifically, we integrate the concept of shared memberships and other spatial attributes into the Speaker‐Listener Label Propagation (SLPA) algorithm, termed the spatially constrained SLPA (or ScSLPA), and apply it to six representative areas in the U.S. The results show that overlapping CSAs tend to form in areas that are more urbanized, with higher localization index (LI) values, larger populations, and shorter travel times than discrete CSAs. Two CSAs in Los Angeles and San Diego are consistent with the catchment areas (CAs) of the National Cancer Institute (NCI)‐designated cancer centers, and other CSAs are much smaller than the CAs of their anchoring cancer centers. The study has important implications for public health policy to advance cancer control and prevention efforts.