Incidence of Multiple vs First Cutaneous Squamous Cell Carcinoma on a Nationwide Scale and Estimation of Future Incidences of Cutaneous Squamous Cell Carcinoma

This cohort study calculates annual age-standardized incidence rates for histopathologically confirmed first and multiple cutaneous squamous cell carcinoma per patient and estimates future cutaneous squamous cell carcinoma incidence rates up to 2027. Question What are the trends in age-standardized incidence rates of cutaneous squamous cell carcinoma (cSCC) from 1989 to 2017 and the estimated trends up to 2027 in the Netherlands and how are these rates associated with the inclusion of multiple cSCCs per patient? Findings This cohort study found that, between 1989 and 2017, age-standardized incidence rates of a first cSCC almost tripled for male patients and increased almost 5-fold for female patients; a further 10-year increase of 23% among male patients and 29% among female patients was estimated. Counting multiple cSCCs per patient additionally increased the cSCC burden by approximately 58% for men and 35% for women. Meaning These findings call for revision of skin cancer health policies to cope with and subsequently halt the high increase in cSCC incidence. Importance Until now, most studies on cutaneous squamous cell carcinoma (cSCC) incidence rates concerned only the first cSCC per patient. Given the increase in incidence rates and the frequent occurrence of subsequent cSCCs per patient, population-based data on the incidence rates of both first and multiple cSCCs are needed. Objectives To calculate annual age-standardized incidence rates for histopathologically confirmed first and multiple cSCCs per patient and to estimate future cSCC incidence rates up to 2027. Design, Setting, and Participants A nationwide population-based epidemiologic cohort study used cancer registry data on 145618 patients with a first histopathologically confirmed cSCC diagnosed between January 1, 1989, and December 31, 2017, from the Netherlands Cancer Registry and all patients with multiple cSCCs diagnosed in 2017. Main Outcomes and Measures Age-standardized incidence rates for cSCC-standardized to the European Standard Population 2013 and United States Standard Population 2000-were calculated per sex, age group, body site, and disease stage. A regression model with positive slope was fitted to estimate cSCC incidence rates up to 2027. Results A total of 145618 patients in the Dutch population (84572 male patients [58.1%]; mean [SD] age, 74.5 [11.5] years) received a diagnosis of a first cSCC between 1989 and 2017. Based on incident data, European Standardized Rates (ESRs) increased substantially, with the highest increase found among female patients from 2002 to 2017, at 8.2% (95% CI, 7.6%-8.8%) per year. The ESRs for first cSCC per patient in 2017 were 107.6 per 100000 person-years (PY) for male patients, an increase from 40.0 per 100000 PY in 1989, and 68.7 per 100000 PY for female patients, an increase from 13.9 per 100000 PY in 1989, which corresponds with a US Standardized Rate of 71.4 per 100000 PY in 2017 for men and 46.4 per 100000 PY in 2017 for women. Considering multiple cSCCs per patient, ESRs increased by 58.4% for men (from 107.6 per 100000 PY to 170.4 per 100000 PY) and 34.8% for women (from 68.7 per 100000 PY to 92.6 per 100000 PY). Estimation of ESRs for the next decade show a further increase of 23.0% for male patients (ESR up to 132.4 per 100000 PY [95% prediction interval, 125.8-139.0 per 100000 PY]) and 29.4% for female patients (ESR up to 88.9 per 100000 PY [95% prediction interval, 84.3-93.5 per 100000 PY]). Conclusions and Relevance This nationwide epidemiologic cohort study suggests that incidence rates of cSCC keep increasing, especially among female patients, and that the occurrence of multiple cSCCs per patient significantly adds to the current and future burden on dermatologic health care. Revision of skin cancer policies are needed to halt this increasing trend.