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

Abstract

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 145 618 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 145 618 patients in the Dutch population (84 572 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 100 000 person-years (PY) for male patients, an increase from 40.0 per 100 000 PY in 1989, and 68.7 per 100 000 PY for female patients, an increase from 13.9 per 100 000 PY in 1989, which corresponds with a US Standardized Rate of 71.4 per 100 000 PY in 2017 for men and 46.4 per 100 000 PY in 2017 for women. Considering multiple cSCCs per patient, ESRs increased by 58.4% for men (from 107.6 per 100 000 PY to 170.4 per 100 000 PY) and 34.8% for women (from 68.7 per 100 000 PY to 92.6 per 100 000 PY). Estimation of ESRs for the next decade show a further increase of 23.0% for male patients (ESR up to 132.4 per 100 000 PY [95% prediction interval, 125.8-139.0 per 100 000 PY]) and 29.4% for female patients (ESR up to 88.9 per 100 000 PY [95% prediction interval, 84.3-93.5 per 100 000 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.

Figure 1.. European Standardized Rate (ESR) and Joinpoint Analyses of Cutaneous Squamous Cell Carcinoma (cSCC) in the Netherlands for Male and Female Patients

A, Main analysis: ESRs per 100 000 person-years for the period from 1989 to 2017 and joinpoint analyses with estimated annual percentage change (APC) for the period from 1989 to 2015, in dark blue for male patients and orange for female patients. The gray background for the period from 2012 to 2015 depicts a spurious flattening owing to nonregistration of patients with cSCC who were increasingly treated in private practices in this period. The light blue background for the years 2016 to 2017 emphasizes the optimized cSCC registration method. The dashed portions of the lines from 2015 to 2017 indicate that no trend analyses were conducted for this period. B, Revised analysis: ESRs per 100 000 person-years and estimated APCs for the period from 1989 to 2017, without the years 2013 to 2015, in dark blue for male patients and orange for female patients. This curve reflects the true burden of cSCC most accurately. ^aSignificant APC value.

Figure 2.. Distribution of Number of Patients With Single and Multiple Cutaneous Squamous Cell Carcinomas (cSCCs) in 2017

A, Patients with 1 or multiple cSCCs in 2017, including their sex and age distribution. B, Distribution of multiple cSCCs (2, 3, or ≥4) per patient in the same year. IQR indicates interquartile range.