Declining invasive and rising in situ melanoma incidence trends in Iceland: A nationwide cohort study.

Background: Melanoma is increasing worldwide, with incidence rates of invasive melanoma and melanoma in situ (MIS) varying by country.

Objective: To provide updated invasive melanoma and MIS incidence and mortality trends in Iceland and explore differences among sex and rurality.

Methods: In this whole-population study using the Icelandic Cancer Registry, patients diagnosed with invasive melanoma or MIS between 1957 and 2021 were included. Sex-specific world standardized incidence (WSR) and mortality rates were assessed by rurality. Joinpoint analysis was used to calculate trends using annual per cent change (APC).

Results: Invasive melanoma incidence rates increased from 0.66 to 7.0 (men) and 1.6 to 11.0 (women) per 100,000 person-years, and from 0.2 to 4.0 and 0.9 to 9.5 per 100,000 person-years for MIS in men and women, respectively, with a statistically significant linear trend (p = 0.001). WSR peaked in both men and women (10.7, 17.9 per 100,000 person-years) between 2002 and 2006 and has since been trending down. Between 1991 and 2005, the rise in invasive melanoma occurred more frequently in urban regions. Between 2003 and 2005, joinpoint analysis demonstrated a downtrend in invasive melanoma in men and women (-0.29, -0.73; p < 0.05). For MIS, the WSR peaked at 12.4 per 100,000 person-years in women between 1997 and 2001 before down-trending to 4.2. In recent years (2017-2021), the WSR has been steadily increasing in women with an APC of 1.43. Melanoma-specific mortality has decreased since 2012 (-0.07; p < 0.05).

Conclusions: Declining invasive melanoma incidence and mortality rates in conjunction with the recent rise in MIS may reflect the impact of Iceland's sun safety and anti-sunbed educational campaigns, federal regulation of sunbeds and earlier melanoma detection in urban areas.