Non-melanoma keratinocyte skin cancer (NMSC) is a significant health risk globally, including in New Zealand, but critical gaps in knowledge of the true prevalence exist due to the absence of data in the New Zealand Cancer Registry. To address this, we conducted a comprehensive study on population prevalence and epidemiological trends of NMSC in New Zealand between 2008 and 2022. Our first analysis provides essential insights into NMSC in the New Zealand context but provides insight for other similar populations.
The main goal of this study was to examine how common skin cancer is in New Zealand, considering the age, gender, and types of tumours found in patients. Our findings show that the prevalence of basal cell carcinoma (BCC) tends to increase with age, especially after 30 years old, and then stabilizes after 50. Compared to squamous cell carcinoma (SCC), BCC is three times more prevalent in the age group of 31–50 years. On the other hand, SCC becomes more common after age 30 and starts approaching BCC’s prevalence after 50. After 80, SCC is even more prevalent than BCC. Overall, we found that the prevalence of BCC has not significantly changed from 2008 to 2022, but we have observed a significant increase in the prevalence of SCC. This trend may be due to the ageing population, which could lead to a stabilization of BCC and an increase in SCC but could also be related to climate change. It has been estimated by others that a 2°C (3.6°F) increase in ambient temperature could potentially increase skin cancer incidence 11% by 2050 [17].
According to our study, males are more likely to develop NMSC than females. This founding can be explained by various factors, including the higher levels of occupational sun exposure experienced by men in jobs such as construction. Additionally, males tend to have lower adherence to sun protection practices than females, contributing to the higher incidence of NMSC among men. However, it is essential to note that the total number of patients diagnosed with BCC was 3,355 in males, compared to 2,422 for SCC. Similarly, the total number of BCC cases in females was 2,300 compared to 2,078 for SCC. These figures indicate that males have a higher incidence of BCC than females. Specifically, BCC’s prevalence in males is 1.5 times greater than in females, while SCC in males is only 1.2 times higher than in females. Promoting awareness and proactive measures can reduce BCC’s burden and improve male health outcomes.
Our study reveals that actinic keratosis, representing a precancerous lesion that leads to SCC, exhibits the highest prevalence among the studied subtypes. It has been reported previously that of NMSC subtypes, BCC is the most prevalent, followed by SCC [18]. Notably, nodular BCC is the most common subtype within the BCC category. It is worth highlighting that NMSC is closely associated with cumulative sun exposure over an individual’s lifetime, often resulting from both prolonged and repeated intermittent exposure to sunlight. Early in-situ SCC are the most frequently observed subtype within the SCC category.
The second objective of this analysis was to investigate the variations in tumour types across different body sites. The study of various body sites revealed variations in the prevalence of BCC and SCC. Considering that prolonged exposure to UV light is a significant risk factor for SCC [19], that typically manifests in sun-exposed areas, our study revealed a higher likelihood of SCC occurrence in the face and limbs compared to the back. Conversely, for BCC, intermittent sun exposure assumes greater importance as a risk factor than sustained sun exposure [20]. Consequently, our findings also indicated a higher probability of BCC occurrence in the face and back than in the limbs. Specifically, BCC’s prevalence was approximately 2 to 3 times higher than SCCs for the back, eyes, neck, and nose. On the other hand, for the lower limbs, upper limbs, and scalp, the prevalence of SCC was found to be 2 to 3 times higher than that of BCC. Similar prevalence of SCC and BCC were observed in the ear, lips, and face.
Our analysis, consistent with previous studies, shows significant differences in the distribution of NMSC among body sites according to gender. Males have a higher prevalence of NMSC overall compared to females. However, we found that female patients have a higher incidence of BCC on their lips, while SCC is more common in the nose and extremities. These differences may be due to factors such as increased cosmetics such as lipstick use on the lips by women.
Our analysis aimed to explore the prevalence of NMSC in various economic regions. The study conducted by [21] discovered a positive correlation between the prevalence of NMSC and the region's socioeconomic status, which is consistent with our findings. A few factors may explain this connection. For example, as communities experience economic growth, people tend to have more leisure time for outdoor activities that involve sun exposure, like beach activities, outdoor sports, or gardening. Regions with higher economic levels may have an ageing population due to greater longevity, and income may correlate with fairer skin in New Zealand, further contributing to the observed association.
In conclusion, international evidence describes distinct geographic and ethnic variations in non-melanoma skin cancer prevalence and incidence. Yet, many skin cancer registries, including in places like New Zealand with known high skin cancer rates, do not record such data, leading to a dearth of knowledge. Therefore, there are few epidemiological studies that detail clinical, disease and socioeconomic indicators within a cohorts’ demographic assessments of NMSC prevalence in different socioeconomic groups has not been reported previously.
This study represents the first ever comprehensive assessment of NMSC prevalence in New Zealand that considers across various demographic factors, including age group, gender, economic status, and tumour subtype. Based on detailed pathological data obtained from patients, the study showed that the prevalence of NMSC was clearly age-related, but also had gender-specific preferences. Additionally, the research underscores disparities in the prevalence rates BCC and SCC across body sites and genders. The study was done over a 15-year period and also offers insights into changes in prevalence that could occur due to the changing climate
Therefore, awareness of this data in the public domain may encourage people take appropriate measures to prevent skin cancer, such as using sunscreen, wearing protective clothing, seeking shade, and reporting suspicious skin lesions to healthcare professionals. It also helps clinical practice and health services planning and offers insights into future trends due to the changing climate. Identification of the population groups most at risk of diagnosis with, and poor outcomes from skin cancer offers health authorities the data needed to implement clinical practice and health system changes to target those who could benefit most from early disease detection and treatment. Healthcare providers can also optimise disease management strategies and improve overall patient outcomes by targeting these specific at-risk groups.
Contributors
S.P conceptualised the study and research project, curated the data, led the formal supervision of analysis and methodology and wrote the final draft.
Y.C was involved in the analysis, methodology, visualisation, and writing of the original draft.
M.M was involved with methodology and supervision of the research study.
All authors reviewed and edited the final manuscript.
Data sharing statement
The data for this study were provided by the Skin Surgery Clinic and may be available to other researchers who meet data access and other research requirements. Please contact the corresponding author via email [email protected] for further details on eligibility and data provision.