Skin cancers

Dermatologists defend traditional methods for melanoma detection

Photographic technologies are increasingly being used in melanoma surveillance despite a lack of evidence of benefit on outcomes such as mortality, a group of clinicians in Queensland say.

Total body photography (TBP) and serial digital dermoscopic imaging (SDDI) are now recommended in guidelines for detection of melanoma but have yet to be evaluated in studies that compare them with traditional screening methods, according to doctors from South East Dermatology, Brisbane.

In a paper (link here) published in the Australasian Journal of Dermatology they says studies of TBP and SDDI have used registry data as a comparator rather than a more appropriate control group of people who have undergone full skin examination using loupe magnification and dermoscopy and targeted biopsy of suspect lesions.

None of the studies of photographic aides have demonstrated improved survival and they argue that there is a possibility that photographic monitoring and observation of lesions may lead to delayed excision and the risk of melanoma progressing from a lower to a higher risk category.

“When dermoscopy was first introduced its utility was demonstrated in studies comparing it with naked-eye examination. It is unclear why this same rigour was not applied in studies of TBP and SDDI,” they write.

The authors, led by Dr Hilary Brown and Dr James Muir note that studies using photographic surveillance have shown lower ratios of in-situ to invasive melanoma, whereas the traditional surveillance methods used with immediate biopsy of suspect lesions  – as used in their practice – resulted in high in situ to invasive ratios.

Photographic surveillance using TBP and/or SDDI reported in-situ was associated with invasive ratios of 0.59:1 to 2.17:1, a review of 11 studies showed.

By comparison, their analysis of data for 492 patients managed by three specialist dermatologists using only traditional surveillance methods showed an in-situ to invasive melanoma ratio of 4.6:1, based on 505 of 615 melanomas diagnosed (82%) being in situ.

Of the in situ melanomas, 43.3% were lentiginous or lentigo maligna and 41.6% were superficial spreading melanomas (SSM), whereas for invasive melanomas, 24.3% were lentigo maligna melanoma and 59.5% were SSM.

Of the invasive melanomas diagnosed in their practice, 85.5% had a Breslow thickness <0.8 mm, 9.1% were 0.8–1 mm and 5.5% were >1 mm.

The authors noted that 48.4% of melanomas were diagnosed by shave procedures.

Reviewing risk factors for a random sample of 14% of the patients they noted that 25% were very-high-risk and 43% had a history of melanoma. Keratinocyte carcinoma was diagnosed by biopsy at 26.1% of visits.

The study authors acknowledged that it was not possible to calculate the number needed to biopsy (NNB) from their retrospective data because it was collected for patients with a confirmed rather than suspected melanoma diagnosis.

And while direct comparisons of the in-situ to invasive ratios were not possible due to differences in patient and clinician characteristics, they said the disparity must “raise the concern that monitoring rather than removing lesions suspicious for melanoma risks patient safety,”

“Whether this is a significant risk and whether patient outcomes would be better under traditional surveillance or TBP and/or SDDI is unknown. This concern should be addressed by prospective, controlled studies comparing traditional surveillance with immediate surgery to photographic surveillance,” they suggested.

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