Abstract and Introduction
Background: An epidemic of basal cell carcinoma (BCC) has led to a significant healthcare burden in white populations.
Objectives: To provide an update on incidence rates and tumour burden in an unselected, geographically isolated population that is exposed to a low level of ultraviolet radiation.
Methods: This was a whole-population study using a cancer registry containing records of all cases of BCC in 1981–2017. We assessed BCC incidence according to age, residence and multiplicity and assessed trends using join-point analysis. Age-standardized and age-specific incidence rates were calculated along with cumulative and lifetime risks.
Results: During the study period, the age-standardized incidence rates increased from 25·7 to 59·9 for men, and from 22·2 to 83·1 for women (per 100 000). Compared with the single-tumour burden, the total tumour burden in the population was 1·72 times higher when accounting for multiplicity. At the beginning of the study period, the world-standardized rates in men and women were similar, but by the end of the study period the rates were 39% higher in women (83·1 per 100 000, 95% confidence interval 77·9–88·3) than in men (59·9 per 100 000, 95% confidence interval 55·6–64·2). This increase was most prominent in women on sites that are normally not exposed to ultraviolet radiation in Iceland: the trunk and legs.
Conclusions: This is the only reported population in which the incidence of BCC is significantly higher in women than in men. The period of notable increase in BCC lesions correlates with the period of an increase in tanning beds and travel popularity. The high multiplicity rates suggest that the total tumour burden worldwide might be higher than previously thought.
Basal cell carcinoma (BCC) is the most common cancer in white populations,[1,2] and associated healthcare costs have become an increasing burden.[2,3] Although BCCs are historically associated with male sex and increasing age, recent population studies have reported a rapid increase in incidence among younger individuals, especially women. This trend may lead to an exponential increase in the overall occurrence of BCCs.[4,5]
As BCCs are not a reportable disease in most countries, they are not included in most national cancer registry incidence reports. Because of this, the majority of data on BCC incidence come from local studies of incidence in well-defined geographical regions. Furthermore, in a large number of registries only the first case of BCC is reported, and subsequent tumours are excluded. Consequently, the true incidence and tumour burden of BCC remain unknown and are probably underestimated. Based on data from the Icelandic Cancer Registry (ICR), a population-based national cancer registry, it was possible to analyse incidence trends and multiplicity from 1981 to 2017 by taking advantage of the complete records of pathologically confirmed BCCs diagnosed within this time period. This registry afforded a unique opportunity to combine histological confirmation of keratinocyte cancers with tumour registry verification over an extensive time period for an entire population, while simultaneously looking at multiplicity.
BCC incidence has a strong relationship with skin colour and an inverse relationship with latitude. Reykjavik is the northernmost capital in the world, with no other capital having a lower overall background ultraviolet index (UVI). The Icelandic population therefore represents an interesting contrast to Australia's population, which has the highest reported BCC incidence rates in the world. Tanning beds are a known risk factor for BCCs, and use in Iceland increased tremendously from the 1980s up until 2004. Studying the Icelandic population may therefore provide important information regarding the behaviour of these cancers.
The British Journal of Dermatology. 2020;183(5):847-856. © 2020 Blackwell Publishing