Spatial Analysis of Skin Cancer: Separating Body Parts Exposed and Not Exposed to the Sun

Abstract

Introduction: Skin cancer is among the most common cancer categories with an increasing global trend of incidence rate. This study explores the spatial distribution of skin cancer, considering body sites exposed and not exposed to sunshine separately. Methods: We used 4302 skin cancer cases recorded by Fars Cancer Registry in southwestern Iran for over six years (2011-2017). The variables included in the study were patients' residence address, gender, age, report date, and final topographical code. The patients' addresses were geocoded to the counties of the study area. Skin cancer sites were categorized based on sun exposure in male and female cases. We used the empirical Bayesian smoothing approach to estimate the skin cancer incidence rate at the county level. Finally, Anselin's Local Moran's Index was used to identify the high-risk skin cancer occurrence areas. Results: In general, skin cancer incidence increased in the study area over the study period (mid-March 2011 to mid-March 2017). Out of 4302 patients with skin cancer, 2602 cases (60%) were male. The age- and sex-specific rate of reported cases with skin cancer was higher in the 80-89 age group (in both male and female genders) compared to other age groups. There were some high-risk spatial clusters of skin cancer in the study area. Further investigations are required to identify the underlying cause of the formation of these clusters.Conclusions: Patients exposed to sunshine, especially among the male group, experienced much higher rates of cancer occurrence as compared to unexposed individuals. With a heterogeneous spatial pattern, hotspots were identified in non-sun-exposed and sun-exposed categories in the study area. Researchers and policymakers can significantly benefit from the spatial analyses of skin cancer incidence. These analyses can provide useful and timely prevention policies as well as tailored monitoring techniques in high-risk regions.