Acta Demato-Venereologica 98-3CompleteContent | Page 24

382 SHORT COMMUNICATION Incidence of Actinic Keratosis and Risk of Skin Cancer in Subjects with Actinic Keratosis: A Population- based Cohort Study Ji Hyun LEE 1 , Yeong Ho KIM 1 , Kyung Do HAN 2 , Young Min PARK 1 , Jun Young LEE 1 , Yong Gyu PARK 2# * and Young Bok LEE 3# * Department of Dermatology Seoul St Mary’s Hospital, College of Medicine, The Catholic University of Korea, 2 Department of Biostatistics, College of Medicine, The Catholic University of Korea, 222, Banpo-daero, Seocho-gu, Seoul, 06591, and 3 Department of Dermatology, Uijeongbu St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea. *E-mail: ygpark@catholic. ac.kr, [email protected] # These authors contributed equally to this work. 1 Accepted Nov 24, 2017; Epub ahead of print Nov 28, 2017 Actinic keratosis (AK) is characterized by a prolifera- tion of atypical keratinocytes in the epidermis. AK occurs mainly in middle-aged and older, fair-skinned, subjects, and is related to chronic exposure to ultraviolet light (UV) (1). Non-melanoma skin cancers (NMSCs) (i.e. basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)) are the most common type of skin cancers. The rate of progression from AK to SCC is va- riably reported as 0.25–20% per year (2, 3). Few studies have examined the incidence of NMSCs and malignant melanoma (MM) among Asian patients with an initial diagnosis of AK, as assessed through long-term follow- up. This study analysed the incidence of AK and the risk of skin cancer in patients with AK based on data obtained from the National Health Insurance System (NHIS) in South Korea. MATERIALS AND METHODS This study utilized nationwide data from January 2006 through December 2015. Data were analysed from patients over 40 years of age who visited clinics or hospitals with a diagnostic code (International Classification of Diseases 10 th revision; ICD-10) of AK (L570) more than once in a given year. A detailed description of the data source and methodology of this retrospective study is given in Appendix SI 1 . RESULTS The total number of NHIS registrations involving indi- viduals > 40 years of age in the period 2006 to 2015 was 229 millions. The corresponding number of patients with AK was 77,975 (Table SI 1 ). The incidence rate increased from 17.94 to 53.99 per 100,000 person-years between 2006 and 2015. After adjusting for age, the incidence also increased strikingly, from 19.57 to 52.86 per 100,000 person-years, between 2006 and 2015. We also analysed AK patients aged 40 years or older in 2015 (Table SII 1 ). The incidence rates of AK per 10,000 person-years in- creased consistently with age (Table SII 1 and Fig. S1 1 ). It is notable that the incidence rate increased sharply for persons in their 70s (Fig. S1 1 ). In 2015, the prevalence of https://www.medicaljournals.se/acta/content/abstract/10.2340/00015555-2854 1 doi: 10.2340/00015555-2854 Acta Derm Venereol 2018; 98: 382–383 AK per 10,000 people was 1.95, 4.00, 9.43, 21.90, and 31.81, for persons aged in their 40s, 50s, 60s, 70s, and 80s, respectively. Patients diagnosed with AK between 2006 and 2014 were followed up until 2015. Our analysis included 63,935 subjects who were diagnosed with AK (Table I). Of these AK patients, follow-up revealed 464 cases that had developed in situ SCC (Bowens disease; BD) 983 cases with NMSC, and 71 cases with MM in their 80s. The hazard ratio (HR) for individuals developing skin cancer was evaluated in patients with AK, with the reference age range of 40–49 years. The HR for BD, NMSC, and MM was 9.25, 3.95, and 5.82, respectively, in patients with AK between the ages of 70 and 79 years. In patients with AK aged 80 years or older, the HR for BD, NMSC, and MM was 14.18, 5.69, and 7.47, respec- tively. In addition, the HR for subjects who develop skin cancer was higher in women than in men. DISCUSSION AK is a common potentially premalignant disease, and occurs mostly on areas of the skin with high levels of exposure to the sun. Age, male sex, skin type, and cumulative exposure to the sun are considered inde- pendent risk factors for AK (4). In this large study, the incidence of AK increased from 19.57 in 2006 to 52.86 per 100,000 person-years in 2015. The present study showed that the incidence of AK in South Koreans was much lower than that of the Western population (5, 6). This difference is thought to be due to differences in skin types, or geographical areas, ethnicity or lifestyle. Consistent with previous reports, this study showed that the incidence and prevalence of AK increased notably with age (7–9). AK, BD and SCC have been shown to share a com- mon pathomechanism, which includes a mutation in the p53 gene (10). Previous reports have shown that 65–72% of cutaneous SCCs arise from AKs in Cauca- sians (11, 12). In a recent systematic review, progres- sion rates of AK to SCC were shown to be 0~0.075% per lesion-year (3). BCC developed in 36% of lesions diagnosed clinically as AKs in the USA (12). Foote et al. (13) reported that the estimated incidence of BCC This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2018 Acta Dermato-Venereologica.