(Reuters Health) – Non-melanoma basal and squamous cell skin cancer incidence surged 30% between 2003 and 2017, a study of residents in Ontario, Canada, suggests.

Researchers examined data from administrative health claims databases and from death certificates for adult residents of Ontario between 1998 and 2017. They calculated the incidence and mortality of keratinocyte carcinoma, with subgroup analysis by sex, age, and income quintile.

Early in the study period, from 1998 to 2003, the crude incidence of keratinocyte carcinoma diagnoses declined from 328.6 to 274.2 per 100,000 adults, the analysis found. This trend then reversed, climbing steadily to 356.7 cases per 100,000 by the final year of the study.

“Possible explanations for the rising incidence during our study period include increased sun exposure and use of indoor tanning beds, which are more common among younger women,” said senior study author Dr. An-Wen Chan, a professor of medicine at the University of Toronto.

Incidence rates were higher among females younger than 55 years old, and in males over 55 years old, suggesting sex and age-based differences in exposure to risk factors for these malignancies, the study team notes in CMAJ.

Between 2008 and 2017, the annual percent change in incidence rates rose more steeply in females than males aged 45 to 54 years (1.2% vs 0.5%) and aged 55 to 64 years (1.2% vs 0.1%).

Over the entire 20-year study period, the mortality rate of keratinocyte carcinoma was 1.8 times higher in males than females, on average, the study also found. Mortality also climbed almost five-fold during the study period, with an annual percent change of 8.9% for females and 8.0% for males.

“The rising mortality rates among both men and women could be due the tumors being diagnosed and treated at a later advanced stage, or tumors becoming more aggressive overall,” Dr. Chan said by email.

One limitation of the study is that the claims data didn’t provide insight into whether tumors were treated without biopsy or surgery, the researchers point out. It also wasn’t possible from the available data to distinguish between basal versus squamous cell carcinoma or determine tumor stage at diagnosis.

“With better data extrapolation from electronic health records and development of more comprehensive cancer registries the true incidence of keratinocyte carcinoma will likely increase,” said Dr. Alex Glazer, a founder of the Dermatology Science and Research Foundation and medical director of Glazer Dermatology in Chicago, Illinois.

“The increased mortality from keratinocyte carcinoma in young women is concerning and highlights the importance of getting regular skin examinations and seeking dermatologic evaluation for any skin lesions that are new, bleeding, growing or changing,” Dr. Glazer, who wasn’t involved in the study, said by email.

As skin cancer incidence continues to rise, clinicians should remain vigilant of keratinocyte carcinomas when evaluating a patient’s skin, Dr. Glazer said.

“Routine screening with a dermatologist has been shown the help identify skin cancers earlier when they are more easily treatable,” Glazer said.

SOURCE: https://bit.ly/3oAFt8c CMAJ, online October 4, 2021.

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