Invasive and in situ squamous cell carcinoma of the skin: a nationwide study in Iceland.

BACKGROUND: The worldwide incidence of cutaneous squamous cell carcinoma (cSCC) is increasing. OBJECTIVES: To evaluate the tumour burden of in situ and invasive cSCC in Iceland, where the population is exposed to limited ultraviolet radiation. METHODS: This whole-population study used the Icelandic Cancer Registry, which contains records of all in situ and invasive cSCC cases from 1981 to 2017. Incidence of cSCC was evaluated according to age, anatomical location, residence and multiplicity, and trends were assessed using joinpoint analysis. Age-standardized rates (WSR) and age-specific incidence rates per 100 000 person-years were calculated, along with cumulative and lifetime risks. RESULTS: Between 1981 and 2017, in situ cSCC WSR increased from 1·2 to 19·1 for men and from 2·0 to 22·3 for women. Invasive cSCC WSR rose from 4·6 to 14 for men and from 0·3 to 13·2 for women. The average number of in situ cSCC lesions was 1·71 per woman and 1·39 per man. Women developed more in situ cSCCs than invasive cSCCs in almost all anatomical locations, whereas men developed more invasive cSCCs, mostly on the head and neck. The rates of in situ cSCC were higher in Reykjavik compared with rural areas. Furthermore, women more commonly developed multiple in situ lesions. For lip cSCCs, invasive lesions occurred more frequently than in situ lesions among both sexes. Joinpoint analysis showed that in situ cSCC in women exhibited the most rapid incidence increase. CONCLUSIONS: cSCC has become an increasingly significant public health problem in Iceland. Tanning bed use and travelling abroad may contribute to skin cancer development. Public health efforts are needed to stem the behaviours leading to this rapid rise in cSCC.

Basal cell carcinoma: an emerging epidemic in women in Iceland.

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. What is already known about this topic? Basal cell carcinoma (BCC) is becoming an increasing healthcare burden worldwide, especially in white populations. Recent population studies have reported a rapid increase in incidence among younger individuals, especially women. What does this study add? Iceland is the only reported population in which the incidence of BCC is significantly higher in women than in men, and there does not seem to be a clear relationship between latitude and BCC incidence in Europe. Men might be comparatively protected in the northern low-ultraviolet environment, with tanning beds and travel abroad likely playing important roles in the observed incidence increase, especially in women. The high multiplicity rates suggest that the total tumour burden worldwide might be higher than previously thought. Linked Comment: Pandeya. Br J Dermatol 2020; 183:799-800.