Detection and Diagnosis of Skin Cancer in South-East Queensland

Introduction Skin cancer is the most common cancer diagnosed in Australia, and the burden is increasing primarily due to an ageing and increasing population. Historically in Australia the vast majority of skin cancers are diagnosed and managed within general practice. More recently primary care has witnessed the emergence of skin cancer clinics as an alternative to ‘mainstream’ general practice. This emergence has not been without controversy, primarily around issues such as diagnostic ability; skin cancer management strategies; and whether those at risk are more likely to attend skin cancer clinics over mainstream general practice. However to date, this debate has not been based on empirical evidence. Aims The aims of this thesis are firstly: to describe and compare the body site distribution of skin cancer, premalignant (actinic keratosis) and common benign pigmented skin lesions excised by doctors working in ‘mainstream’ general practice and skin cancer clinics; secondly, to describe and compare the accuracy of doctors working in ‘mainstream’ general practice and skin cancer clinics in diagnosing skin cancer; and finally to describe and compare the sociodemographics and skin cancer risk profiles, reasons for choice of service provider and perceived access to services of patients attending ‘mainstream’ general practice and primary care skin cancer clinics. Methods This prospective comparative study included 104 general practitioners (GPs) and 50 skin cancer clinic doctors and included 28,755 patient encounters. Additionally, 301 GP patients and 852 skin cancer clinic patients completed self-administered questionnaires following their skin examination. Descriptive statistics were used to examine the profiles of participating doctors, patients and the casemix of skin lesions. To examine the body site distribution of excised skin lesions, relative tumour densities (RTD) were calculated. Logistic regression models were used to estimate diagnostic accuracy using measures such as sensitivity; specificity; positive predictive value (PPV); and negative predictive value (NPV). The number of lesions needed to excise (NNE) for each malignant lesion was also calculated. A logistic regression model was used to examine factors associated with a patient’s choice of service provider (GP versus skin cancer clinics). All analyses were adjusted for clustering accounting for individual doctor and doctors within the same practice. Results Skin cancer clinic doctors excised significantly more BCCs than general practitioners who excised more SCCs. However, the overall proportion of all NMSCs excised was similar for the two groups. Compared to the whole body, the highest density for non-melanoma skin cancer and premalignant lesions was observed on chronically sun exposed areas of the body including the face in men and women, the scalp and ears in men, and the hands in women in both general practice and primary care skin cancer clinics. The density of basal cell carcinoma and melanoma was also high on intermittently exposed body sites. Women (p < 0.001), younger patients (p=0.01) and patients with benign naevi (