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

Background: Socioeconomic status (SES) and access to dermatological care are thought to influence rates of keratinocyte carcinoma (KC). However, few studies examine these factors' impact on disease burden of specific KC subtypes.

Objectives: To determine the impact of SES and distance to dermatologist on the burden of KC disease, 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's disease (BD).

Methods: Based on a nationwide registry (The Danish Skin Cancer Registry), the study included 100,705 patients with 190,468 histologically- or clinically verified KC/BD registered in state-funded office-based dermatology practice between 2013-2022. A negative binomial regression calculated TIRRs, while impact on lateral tumour size was estimated with log-linear quantile regression.

Results: High SES, based on income, was associated with increased incidence and smaller tumours for all KC subtypes. Rates of nBCC and sBCC were 2.7 and 2.4 times higher among top-25% earners versus the lowest income category (nBCC: 2.74 (95%CI:2.69-2.79); sBCC: 2.38 (95%CI:2.30-2.47)). However, top earners had up to 9.7% smaller BCC tumours (e.g., BCC: 95%CI:8.5-11.0%). Similarly for SCC and BD, incidences were higher among the top-25% earners (e.g., SCC:2.08 (95%CI:1.94-2.22) but also 11.3% (95%CI:7.4-15.1%) and 13.9% (95% CI:9.9-17.7%) smaller in size.Impact of distance to dermatologist depended on KC subtype. For nBCC, rising incidence was noted with shorter distances, as reflected by a 15% decrease in TIRR with every 10 km increase (0.85(95%CI: 0.85-0.86)). The opposite trend was seen for SCC and BD, where respective incidence rates increased 7% and 14% with every 10 km (e.g., SCC: 1.07(95%CI:1.05-1.09). Individuals living further away had larger nBCCs and sBCCs, with an up to 8.1% (nBCC: 95%CI:7.5-8.7%) increase in tumour size per 10 km. No correlation between size and distance was found for SCC.

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