Trend Analysis of Cutaneous Squamous Cell Carcinoma of the External Lip From 1975 to 2016.

Importance Cutaneous squamous cell carcinoma (cSCC) is the second most common nonmelanoma skin cancer and commonly affects the head and neck. Increasing regional reports of aggressive cases warrant an analysis of population-based trends of cSCC of the head and neck. Objective To assess demographic, clinical, and survival trends among patients with cSCC of the external lip. Design, Setting, and Participants This was a retrospective, population-based cohort study of 15 171 cases of cSCC of the external lip registered in the Surveillance, Epidemiology, and End Results (SEER) database between 1975 and 2016. Statistical analyses were conducted in October 2020. Main Outcomes and Measures The primary outcome was clinical characteristics (tumor site, stage, and tumor grade). Demographic characteristics, incidence, treatment characteristics, and survival outcomes were also assessed. Results In total, 15 171 cases of cSCC were extracted from the SEER database (80.3% of patients were male, and 97.0% identified as being of White race/ethnicity). Incidence among male patients decreased from 4.4 to 0.8 per 100 000 during the study period, whereas the female patients' share cases increased from 8.4% in 1975 to 1979 to 26.1% by 2016. Cases increased in the US Pacific Coast and eastern regions, and along the 30° to 39° N latitudinal range, while decreasing in the southwestern region. Of 15 171 cases, 51.2% cases presented at stage I, and 96.2% were nonmetastatic. Cases of grade II and grade III tumors increased between 1975 and 2016. Five-year disease-specific survival remained stable at 95.9%; however, patients older than 75 years experienced worse disease-specific survival (93.2%) associated with decreasing survival trends among patients older than 85 years. Conclusion and Relevance This population-based cohort study found that incidence of cSCC of the external lip decreased among men; however, cases increased along US coastal regions and in more northern US latitudes. Tumor grades were increasingly advanced, and patients older than 85 years should be given special prognosis and treatment consideration.