Anatomic Locations of Procedurally Treated Keratinocyte Carcinomas in the US Medicare Population.

Importance:Keratinocyte carcinomas are the most common cancers in the US. However, keratinocyte carcinomas are not included in US national cancer registries, and information on the anatomic locations of keratinocyte carcinomas is lacking. Objective:To investigate the anatomic location of keratinocyte carcinomas in the US using a large claims data set. Design, Setting, and Participants:We performed a cohort study using a deidentified, random sample of 4 999 999 fee-for-service Medicare beneficiaries aged 65 years or older (2009-2018). Main Outcomes and Measures:Proportion of procedurally treated keratinocyte carcinomas at each anatomic location, identified by linking diagnosis and treatment codes. Results:A total of 2 415 514 keratinocyte carcinomas were identified in 792 393 beneficiaries. The mean (SD) age was 76.6 (8.1) years, 410 364 (51.8%) were women, and 96.7% were White. Of the 2 415 514 keratinocyte carcinomas, 796 542 could be subtyped into basal cell carcinoma (33.0%), 927 984 into squamous cell carcinoma (38.4%), and 690 988 (28.6%) could not be subtyped. The most common location of squamous cell carcinomas was the head and/or neck (44.3%) followed by upper limbs (26.7%). The most common location of basal cell carcinomas was head and/or neck (63.8%), followed by trunk (14.9%). In women, keratinocyte carcinomas were most common on the head and/or neck (47.3%) followed by upper and lower limb (18.5% and 16.6%, respectively). In men, keratinocyte carcinomas were most common on the head and/or neck (58.7%) followed by upper limb and trunk (17.3% and 11.4%, respectively). Conclusions and Relevance:The results of this large Medicare cohort study highlight the anatomic locations of keratinocyte carcinomas over recent years and show the predominance of lesions occurring at head and/or neck anatomic location. This foundational information on keratinocyte carcinoma anatomic locations in the US is valuable for improved keratinocyte risk factor differentiation and skin cancer surveillance.