Study Finds Incidence Rates of cSCC Continue to Increase, Especially Among Females

A dutch nationwide epidemiologic cohort study published in JAMA Dermatology suggests that incidence rates of cutaneous squamous cell carcinoma (cSCC) keep increasing, especially among female patients, and that the occurrence of multiple cSCCs per patient significantly adds to the current and future burden of the disease on dermatologic health care.¹

Study investigators indicated that these results call for the need to revise skin cancer health policies to be able to handle the increasing burden of keratinocyte carcinoma management.

“Full attention is needed to identify high-risk cSCCs or patients at risk for multiple cSCCs to establish efficient follow-up regimens,” the authors of the study wrote. “Ultimately, primary prevention will remain the key strategy to halt the increasing trend in cSCC incidence and the occurrence of multiple cSCCs per patient.”

In this nationwide population-based epidemiologic cohort study, researchers used cancer registry data patients with their first histopathologically confirmed csCC diagnosis between January 1, 1989 and December 31, 2017 from the Netherlands Cancer Registry. In addition, all patients with multiple cSCCs diagnosed in 2017 were also included in the study. In total, 145,618 patients in the Dutch population (84,572 male patients [58.1%]; mean [SD] age, 74.5 [11.5] years) were found to have received a diagnosis of a first cSCC between 1989 and 2017.

Based on incident data, European Standardized Rates (ESRs) were shown to have increased substantially, with the highest increase observed among female patients from 2002 to 2017, at 8.2% (95% CI, 7.6%-8.8%) per year. Moreover, 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; this 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.

When looking at multiple cSCCs per patient, ESRs increased by 58.4% for men and 34.8% for women. Given these results, estimation of ESRs for the next decade predict 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]).

“We also showed that 30% of all cSCCs in a year are missed when only the first cSCC per patient is registered and all subsequent cSCCs are disregarded,” the authors wrote. “This finding corresponds with the underrepresentation of 30% to 50% as found in studies from Australia and New Zealand, emphasizing that the true burden caused by cSCCs is much higher than shown in most studies considering only the incidence of first cSCC per patient.”

Importantly, even with the highly advanced registration system used, the researchers still may have underestimated the cSCC incidence rates, as patients treated by general practitioners or private practices without further hospital referral were not registered until 2016. Additionally, cSCCs diagnosed on the same body site within 3 months of the original diagnosis were considered recurrences and therefore were not counted as new tumors, which may have caused an underestimation of the true number of cSCCs per patient as shown for 2017.

In an editorial written by Mackenzie R. Wehner, MD, MPhil, of the University of Texas MD Anderson Cancer Center, Wehner suggested that the current study highlights the importance of lobbying for research funding for cSCC, obtaining appropriate public health and clinical support for cSCC, and providing accurate information to patients with cSCC.² However, she also indicated that being able to do so depends on the acquisition of high-quality epidemiologic information.

“As a specialty, dermatology needs to continue to strive to improve our knowledge of cSCC epidemiologic characteristics, as well as those of basal cell carcinoma,” Wehner wrote. “We are at a disadvantage in research, public health, and clinical care of these highly incident cancers because of cancer registry obstacles, which makes this work in cSCC epidemiologic characteristics absolutely critical.”

References:

1. Tokez S, Hollestein L, Louwman M, Nijsten T, Wakkee M. Incidence of Multiple vs First Cutaneous Squamous Cell Carcinoma on a Nationwide Scale and Estimation of Future Incidences of Cutaneous Squamous Cell Carcinoma. JAMA Dermatology. doi: 10.1001/jamadermatol.2020.3677

2. Wehner MR. Underestimation of Cutaneous Squamous Cell Carcinoma Incidence, Even in Cancer Registries. JAMA Dermatology. doi: 10.1001/jamadermatol.2020.3678