Shifting landscape in skin cancer incidence: the rising tide of cutaneous squamous cell carcinoma and potential implications for prevention

Cutaneous squamous cell carcinoma (cSCC) is one of the most prevalent cancers and ranks among the fastest-­rising skin cancers worldwide, affecting more than 2 million people annually. Many national cancer registries do not register cSCC or register only the first tumour, resulting in an underestimation of incidence rates (IRs). Recent Dutch population-based studies showed that 30% of all cSCCs are missed annually when only the first cSCC is registered and that the risk of a new cSCC increases steeply after each subsequent cSCC. The increase in cSCC incidence in both sexes, and particularly in women, underscores the need for deciphering underlying factors such as changes in ultraviolet (UV) radiation exposure patterns.

In this issue of the BJD, Olsen et al. investigated this further by comparing nationwide incidence trends in cSCC and melanoma over three decades in seven susceptible populations residing at mid-to-high latitudes in the northern and southern hemispheres. They demonstrated that the ratio of cSCC to melanoma incidence increased over time and with proximity to the equator, the latter being consistent with higher levels of UVB radiation. While the cSCC to melanoma ratio was higher in men than in women, in most countries the cSCC to melanoma IR ratio increased over time to a greater extent in women. As melanoma is more closely related to intermittent sun exposure and sunburns and cSCC has a stronger connection with lifetime sun exposure, these findings suggest that cumulative sun exposure in women has increased more over time. Traditionally, women experienced less sun exposure because they wore more skin-covering clothes, tended to have more indoor occupations and had different recreational habits. Apart from potential changes in UV exposure patterns in women, including sunbed habits, sex differences in healthcare-seeking behaviour could also contribute to the observed trends.