Impact of socioeconomic status and distance to a dermatological clinic on the disease burden of keratinocyte carcinoma and its precursors in Danish office-based dermatological practice

BACKGROUND: Socioeconomic status (SES) and access to dermatological care are known to influence rates of keratinocyte carcinoma (KC). However, few studies have examined the impact of these factors on the disease burden of specific KC subtypes.

OBJECTIVES: To determine the impact of SES and distance to a dermatologist on the burden of KC, determined by tumour incidence rate ratios (TIRRs) and tumour size, for nodular basal cell carcinoma (nBCC), superficial BCC (sBCC), squamous cell carcinoma (SCC) and the KC precursor, Bowen disease (BD).

METHODS: Using data from the nationwide Danish Skin Cancer Registry, our study included 100 705 patients with 190 468 histologically or clinically verified cases of KC/BD registered in state-funded office-based dermatology practices between 2013 and 2022. Negative binomial regression was used to calculate TIRRs; the impact on lateral tumour size was estimated with log-linear quantile regression.

RESULTS: High SES was associated with increased tumour incidence and smaller tumours for all KC subtypes. Rates of nBCC and sBCC were 2.7 times and 2.4 times higher, respectively, among the top 25% earners vs. the lowest income category [nBCC 2.74, 95% confidence interval (CI) 2.69-2.79; sBCC 2.38, 95% CI 2.30-2.47], with top earners having BCC tumours that were up to 9.7% smaller (95% CI 8.5-11.0%). The impact of distance to a dermatologist varied by KC subtype. For nBCC, increasing tumour incidence was noted with shorter distances to a dermatologist, while the opposite trend was seen for SCC and BD. Individuals living further away from a dermatologist had larger nBCC and sBCC tumours. No correlation between tumour size and distance to a dermatologist was found for SCC.

CONCLUSIONS: High SES was associated with increased tumour incidence and smaller tumours for all KC subtypes, reflecting either higher rates of detection or higher rates of disease occurrence. Distance to a dermatologist was an independent predictor of KC burden, with shorter distances leading to increased tumour incidence but smaller nBCC tumours and decreased incidence of SCC.