Study Population

We identified 42,359 cancer survivors alive and aged ≥19 as of 12/31/2016. To be included, patients had to have ≥1 office visit at one of 431 primary care clinics that were actively using an EHR system throughout the three-year study period (2014–2016), and had to have a record in a discrete searchable EHR field (i.e., encounter diagnosis, problem list, medical history) indicating a malignant cancer diagnosis, excluding non-melanoma skin cancer. These cancer survivors represented 3.0% of our CHC patient population within the 19 states with active primary care clinics in the ADVANCE network.

To construct a comparison group, we identified >1.2 million adult patients from the same clinics with no documented cancer diagnosis as of 12/31/2016. This population was younger and had a different sex distribution than cancer survivors; thus, to reduce bias and improve group comparisons, cancer survivors were matched in a 1:3 ratio²⁶ to this comparison group. We matched on sex, year of birth, and primary health system (each patient’s most frequently accessed CHC): for each cancer survivor, 3 matches were selected at random and without replacement. This exact matching method resulted in exclusion of 2,093 cancer survivors because they had <3 control matches available (4.9% of survivors). Excluded patients were more commonly male, non-Hispanic white, and older than included cancer patients. The final dataset contained 40,226 cancer survivors with 47,339 primary cancer sites (as a single patient can have >1 cancer site) and 120,798 matched comparison patients.