Detection and Diagnosis of Skin Cancer in South-East Queensland

Philippa Youl (2011). Detection and Diagnosis of Skin Cancer in South-East Queensland PhD Thesis, School of Population Health, The University of Queensland.

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Author Philippa Youl
Thesis Title Detection and Diagnosis of Skin Cancer in South-East Queensland
School, Centre or Institute School of Population Health
Institution The University of Queensland
Publication date 2011-06
Thesis type PhD Thesis
Supervisor Prof Peter O'Rourke
Prof David Whiteman
Prof Joanne Aitken
Total pages 235
Total colour pages 41
Total black and white pages 194
Language eng
Subjects 11 Medical and Health Sciences
Abstract/Summary 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 (p <0.001) were significantly more likely to exert high levels of pressure to excise a benign pigmented lesion. The casemix of skin lesions excised or biopsied in both settings was relatively similar. Overall, sensitivity for diagnosing any type of skin cancer was not significantly different for GPs (0.91, [95%CI=0.89-0.93]) and skin cancer clinic doctors (0.94, [95%CI=0.92-0.95]) (p=0.78). GPs recorded significantly lower sensitivity for diagnosing melanoma compared to skin cancer clinic doctors (0.29, [95%CI=0.12-0.45]); and 0.60, [95%CI=0.52-0.69], respectively) (p <0.01). There was no significant difference in the number of lesions excised for every skin cancer diagnosed (1.9 [95%CI=1.8-2.1] for GPs and 2.1 [95%CI=1.9-2.3] for skin cancer clinic doctors) (p= 0.50). The sociodemographic and skin cancer risk profile of patients attending a GP and a skin cancer clinic for a skin examination was quite similar, with the exception that GP patients tended to be older (p=0.008). Additional factors associated with an increased likelihood of attending a GP included high annual household income and having a high density of moles. A higher proportion of patients attending a GP did so because they wanted a check of a specific mole or spot compared to skin cancer clinic patients (66.0% versus 43.1%, p < 0.001). Discussion and conclusions Skin cancer is the most common cancer in Australia and represents an enormous burden on the health system. Results showed that while the density of excised skin cancer and premalignant lesions were very high on more chronically exposed body sites, these lesions were also frequently excised from intermittently exposed body sites. This finding highlights the importance of examining the whole of the body, a procedure that was significantly less likely to be conducted in general practice compared to skin cancer clinics. GPs and skin cancer clinic doctors diagnose skin cancer with equally high levels of accuracy. For the most part the demographic and skin cancer risk profiles of patients attending both settings were similar. Providing services to manage skin cancer is a growing challenge in a country with the highest rates of skin cancer in the world. Currently, the relatively low ratio of dermatologists to a population at high risk, coupled with an increasing demand on general practice, means additional avenues to diagnose and manage skin cancer are required. The presence of an established general practice service, and now a newer form of service provision in primary care skin cancer clinics, may help to meet this challenge.
Keyword skin cancer
Skin screening
Primary care
Diagnostic accuracy
Early Detection
Additional Notes Colour pages: 29,32,35,55,67,75,84,87,90,93,105,107,118-123,133,134,173-181,183,184,186-194,209 Landscape: 47,48,52,53,81,101,102,103

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Created: Tue, 29 Nov 2011, 17:58:05 EST by Ms Philippa Youl on behalf of Library - Information Access Service