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- Page navigation anchor for With regard to the comments by Dickinson, Sladden, and Singh,With regard to the comments by Dickinson, Sladden, and Singh,
Thank you to Drs. Dickinson, Sladden, and Singh for their interest in our work. We appreciate the opportunity to address their comments.
Dickinson et al request an age-standardized analysis, which we already reported. A key message of our study was that the incidence and mortality trends were influenced by age, as shown by the annual age- and sex-stratified rates (Figures 2, 3, and S1) as well as the age- and sex-standardized rates (Table 1). These analyses confirmed the rising incidence rates in every age strata (2003 onwards) and rising mortality (1998 onwards). When the rates were adjusted to reflect the incidence in white adults, the annual increases were 50% greater compared with the overall population (Table S1). As mentioned in our results section, the increase in standardized rates was attenuated compared with crude rates.
Dickinson et al also suggest that changes in diagnostic criteria, biopsy practices for precancerous lesions, or coding practices could have led to the observed trends, but we find this unlikely. First, there were no changes in diagnostic criteria for keratinocyte carcinoma during the study period. Second, we only included invasive basal and squamous cell carcinomas (which are objectively diagnosed on biopsy) and we excluded precancerous actinic keratoses and in situ carcinomas. Third, we used a validated insurance claims-based algorithm to identify keratinocyte carcinoma. The performance of this algorithm did not vary over time (...
Show MoreCompeting Interests: None declared.References
- Evan Tang, Kinwah Fung, An-Wen Chan. Incidence and mortality rates of keratinocyte carcinoma from 1998–2017: a population-based study of sex differences in Ontario, Canada. CMAJ 2021;193:E1516-E1524.
- Chan, An-Wen et al. “Application of Recursive Partitioning to Derive and Validate a Claims-Based Algorithm for Identifying Keratinocyte Carcinoma (Nonmelanoma Skin Cancer).” JAMA dermatology vol. 152,10 (2016): 1122-1127. doi:10.1001/jamadermatol.2016.260
- Page navigation anchor for RE: Overdiagnosis and aging population may be responsible for apparent increasing incidence of keratinocyte carcinomasRE: Overdiagnosis and aging population may be responsible for apparent increasing incidence of keratinocyte carcinomas
We congratulate the authors for obtaining data on keratinocyte carcinoma incidence and mortality in Ontario (1). The increasing mortality is concerning. However, we disagree with their main message of rising incidence. There was a steep decrease in incidence in the first 6 years of the study, followed by a slower rise. While Figure 1 shows total population rates, much of that rise is due to the rising proportion of older people in the population. The age-specific rates in Figure 3 show a less dramatic rise, still below the 1998 rates. We ask the authors to perform an age-standardised analysis, since we believe that would demonstrate the current incidence is lower than in 1998, and the mortality rise is less dramatic than crude rates show.
The authors miss much of the story by focussing only on the most recent 10 years without explaining that first drop. The change in 2003 is so abrupt that sun-exposure campaigns are an unlikely explanation. We wonder whether there was a change in diagnosis criteria, coding practice, or other practice change. It is unclear whether the authors included in-situ cancers or not. There are limited pathological characteristics differentiating between actinic keratosis and in-situ SCC and between in-situ and invasive SCC. A small change in diagnostic thresholds could well produce apparent rising incidence as described in this paper. (2)
The rising incidence among young women could herald greater increases in coming years. However, t...
Show MoreCompeting Interests: None declared.References
- Evan Tang, Kinwah Fung, An-Wen Chan. Incidence and mortality rates of keratinocyte carcinoma from 1998–2017: a population-based study of sex differences in Ontario, Canada. CMAJ 2021;193:E1516-E1524.
- Smoller BR. Squamous cell carcinoma: from precursor lesions to high-risk variants. Modern Pathology. 2006; 19, S88–S92
- de Berker D, McGregor JM, Mohd Mustapa MF, Exton LS, Hughes BR. British Association of Dermatologists' guidelines for the care of patients with actinic keratosis 2017. Br J Dermatol. 2017; 176(1): 20-43.