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Original Investigation
October 7, 2020

Assessment of Incidence Rate and Risk Factors for Keratoacanthoma Among Residents of Queensland, Australia

Author Affiliations
  • 1Department of Population Health, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
  • 2Dermatology Research Centre, University of Queensland Diamantina Institute, Brisbane, Queensland, Australia
  • 3Department of Dermatology and Venereology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
  • 4Faculty of Medicine, University of Queensland, Brisbane, Queensland, Australia
  • 5Cancer Research UK Manchester Institute and University of Manchester, Manchester Academic Health Science Centre, Manchester, United Kingdom
JAMA Dermatol. Published online October 7, 2020. doi:10.1001/jamadermatol.2020.4097
Key Points

Question  What are the incidence rate and risk factors for keratoacanthoma?

Findings  In this cohort study of 40 438 residents of Queensland, Australia, the person-based incidence rate for keratoacanthoma was 409 individuals per 100 000 person-years. Older age, male sex, UV radiation exposure–sensitive phenotypes, indications of high sun exposure (such as previous keratinocyte cancer excisions), smoking, and high alcohol use were independently associated with the development of keratoacanthoma.

Meaning  This analysis is, to date, the first large prospective cohort study to quantify the incidence rate and risk factors for keratoacanthoma, many of which are shared with other keratinocyte cancers.

Abstract

Importance  Keratoacanthoma (KA) is a common and generally benign keratinocyte skin tumor. Reports of the incidence rates of KA are scant. In addition, the risk factors for KA are not well understood, although associations with UV radiation exposure and older age have been described.

Objective  To investigate the incidence rate of KA and the risk factors for developing KA.

Design, Setting, and Participants  The study included data from 40 438 of 193 344 randomly selected residents of Queensland, Australia, who participated in the QSkin Sun and Health (QSkin) prospective population-based cohort study. All participants completed a baseline survey between 2010 and 2011 and were ages 40 to 69 years at baseline. Histopathologic reports of KA were prospectively collected until June 30, 2014, through data linkage with pathologic records. Cox proportional hazards models were used to identify risk factors associated with KA while controlling for potential confounding variables. Data were analyzed from January 2 to April 8, 2020.

Exposures  Demographic characteristics, phenotypes, UV radiation exposure, medical history, and lifestyle.

Results  Among 40 438 participants (mean [SD] age, 56 [8] years; 18 240 men [45.1%]), 596 individuals (mean [SD] age, 62 [6] years; 349 men [58.6%]) developed 776 KA tumors during a median follow-up period of 3.0 years (interquartile range, 2.8-3.3 years). The person-based age-standardized incidence rate for KA in the age-restricted cohort was 409 individuals per 100 000 person-years (based on the 2001 Australian population). Risk factors after adjustment for potential confounders were older age (age ≥60 years vs age <50 years; hazard ratio [HR], 6.38; 95% CI, 4.65-8.75), male sex (HR, 1.56; 95% CI, 1.33-1.84), fair skin (vs olive, dark, or black skin; HR, 3.42; 95% CI, 1.66-7.04), inability to tan (vs ability to tan deeply; HR, 1.69; 95% CI, 1.19-2.40), previous excisions of keratinocyte cancers (ever had an excision vs never had an excision; HR, 6.28; 95% CI, 5.03-7.83), current smoking (vs never smoking, HR, 2.02; 95% CI, 1.59-2.57), and high alcohol use (≥14 alcoholic drinks per week vs no alcoholic drinks per week; HR, 1.42; 95% CI, 1.09-1.86).

Conclusions and Relevance  This is, to date, the first large prospective population-based study to report the incidence rate and risk factors for KA. The high person-based incidence rate (409 individuals per 100 000 person-years) highlights the substantial burden of KA in Queensland, Australia. Furthermore, the study’s findings suggest that older age (≥60 years), male sex, UV radiation–sensitive phenotypes, indications of high sun exposure (eg, previous keratinocyte cancer excisions), smoking, and high alcohol use are independent risk factors for the development of KA.

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