Potentially, melanoma is almost totally preventable. Exposure to excess ultraviolet (UV) radiation is the major environmental factor in its development and one which is amenable to behavioural intervention. While melanoma can in the majority of cases be prevented through appropriate sun protection, discussion continues on the feasibility of population screening for melanoma.
Screening tests for melanoma
The screening tests proposed for the early detection of melanoma include total body skin examination by a health care professional or skin self-examination. The use of dermoscopy by experienced health professionals has been found to provide increased diagnostic accuracy. Detection of a suspicious lesion constitutes a positive screening test for which further investigation is required. Melanoma is confirmed by biopsy.
Accuracy of skin examination by a general practitioner or specialist
Due to a lack of research, particularly in the Australian setting, it is difficult to assess differences in levels of accuracy for detecting melanoma between general practitioners (GPs) and specialists. A systematic review published in 2001 concluded there was insufficient data to detect any differences in levels of accuracy in detecting melanoma between dermatologists and GPs.
Accuracy of diagnosing melanoma has been reported in a number of studies, primarily within screening programs. In the majority of screening programs, clinical skin examination has been conducted by specialists with only one study to date assessing outcomes of whole-body skin examinations conducted by GPs. In that study 2.5% of all suspicious skin lesions detected by the GPs that were excised or biopsied were confirmed to be melanoma with a specificity of 86%. Of lesions suspected of being melanoma, 20.5% were confirmed as melanoma on histology. Most other studies have reported positive predictive values (the probability an individual has melanoma given they test positive on the screening exam) values between 0-12.5%, with levels of accuracy increasing when analyses were restricted to those over the age of 50 years. The majority of studies examining clinical accuracy in diagnosing melanoma are not able to report on the sensitivity of the screening program as individuals with negative screens are not followed-up. Fritschi et al. have conducted one of the few studies to follow-up screening participants and reported a sensitivity of 69.7% in the first year after the screening examination.
Aids to clinical diagnosis of melanoma
The use of aids to improve diagnostic accuracy of melanoma is increasing in both specialist and general practice settings. Dermoscopy (surface microscopy, dermatoscopy) uses a hand-held magnifying device to improve visualisation of pigmented skin lesions. Meta-analyses of studies have consistently shown that the use of dermoscopy improves the accuracy of melanoma diagnosis. Other studies within the specialist setting have shown a reduction in rates of excisions of benign lesions. In the general practice setting, studies have shown improvements in sensitivity for melanoma diagnosis for clinicians who have experience in the use of dermoscopy. In a recent study in Western Australia involving 63 GPs who were trained in the use of dermoscopy and short-term sequential digital dermoscopy, significant improvements in the benign to malignant ratio and a 63% reduction in the number of lesions requiring referral or excision was observed. It is recommended that clinicians who routinely examine pigmented skin lesions be trained in the use of dermoscopy.
Total body photography is an additional aid used particularly for individuals at high risk of melanoma such as those with dysplastic naevi. While no randomised-controlled trials have been undertaken, a number of studies have concluded that the use of total body photography has assisted in the detection of early stage melanoma.
Skin self-examination has been suggested as one method to detect melanoma early. More commonly the patient is the first person to detect melanoma. Patients tend to find melanomas when they occur on exposed or visible sites but only a small proportion are found when the patient conducts a deliberate skin examination. The efficacy of skin self-examination in detecting melanoma is not well understood due in part to the variety of definitions of skin self-examination used in studies, and in the difficulty in accurately detailing skin examination practices. Further research into the value of skin self-examination is needed.
Death from melanoma is strongly inversely related to thickness at diagnosis, thus earlier diagnosis might be expected to provide the patient with the best possible chance of long-term survival. There is some evidence to suggest melanomas that are detected during a screening examination are thinner than when detected incidentally. In a large Queensland study melanoma detected during a deliberate skin examination by a doctor was more likely to be thinner than if detected incidentally. Similarly in the American Academy of Dermatology Screening Program, a significantly higher proportion of melanomas detected during screening were thinner compared to that seen in the population-based cancer registries. Recent results from a Queensland case-control study of melanoma provide the strongest evidence to date for the effectiveness of clinical skin examination. In that study involving over 3,700 patients with melanoma, whole-body skin examination by a doctor in the three years prior to melanoma diagnosis was significantly associated with a lower risk of being diagnosed with thicker melanoma.
Skin examination whether by self or by a doctor appears to be increasing in the community. While trends in melanoma in recent years have shown an increase in the incidence of thin melanoma, there has been no corresponding decrease in incidence of thicker lesions. As there are a number of histological types of melanoma, and their growth patterns vary significantly, melanomas that grow more aggressively may not be detected until they are quite advanced. Research is necessary to further our understanding of the impact skin screening has on melanoma incidence and survival.
As there is currently no conclusive evidence that routine skin examination results in a reduction in mortality from melanoma, the NHMRC Clinical Practice Guidelines for Melanoma and the U.S Preventive Services Task Force clinical guidelines currently do not recommend routine screening for the general population.
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