The key to a melanoma cure is early detection before the cancer has spread beyond the epidermal skin layer. Several novel, hand-held, automated optical scanning devices have been developed to aid care providers in early diagnosis. These technologies quickly and non-invasively permit visualization deeper into the skin to detect evidence of malignant change.
The reference standard is visual examination of skin lesions, followed by biopsy and histopathologic analysis, although inter-rater agreement among dermatopathologists varies. Dermoscopy provides additional visual information, increasing diagnostic accuracy, but is not widely used and is time-consuming.
Optical scanners have favourable sensitivity rates (i.e., they identify most melanomas) but show low specificity, meaning that many skin lesions are mislabelled as suspicious and proceed to unnecessary biopsy.
With the most deadly form of skin cancer, melanoma, a huge number of dangerous-looking moles are actually harmless, but has always been impossible to know for sure without an invasive surgical biopsy. Today dermatologists have new help in making the right call — a handheld tool approved by the FDA for multispectral analysis of tissue morphology. The MelaFind optical scanner is not for definitive diagnosis but rather to provide additional information a doctor can use in determining whether or not to order a biopsy. The goal is to reduce the number of patients left with unnecessary biopsy scars, with the added benefit of eliminating the cost of unnecessary procedures. The MelaFind technology (MELA Sciences, Irvington, NY) uses missile navigation technologies originally paid for the Department of Defense to optically scan the surface of a suspicious lesion at 10 electromagnetic wavelengths. The collected signals are processed using heavy-duty algorithms and matched against a registry of 10,000 digital images of melanoma and skin disease.
The Technology
Melanoma is a cancer that begins in melanocytes, which are deep epidermal cells that produce the pigment melanin. In Canada, melanoma is the seventh most common cancer, with about 6,000 new cases estimated in 2013 (3,300 men and 2,700 women) and an age-standardized incidence rate of 13.4 per 100,000 people (15.1 for men and 12.2 for women).
Based on 2007 estimates, the lifetime probability of dying from the disease is 1 in 287 men and 1 in 420 women.
If melanoma is detected at an early stage (less than 1 mm deep), the 5-year survival rate is 93 to 97%; however, the survival rate drops to 10% to 20% with advanced disease. To enable early detection while avoiding unnecessary biopsies, there is a need for accurate diagnostic devices that can differentiate benign skin lesions from malignant ones.
Several non-invasive, automated, hand-held optical scanners have been developed to help dermatologists determine whether a skin biopsy is indicated. Three devices that have been approved in Canada and the US are discussed here. Aura (Verisante Technology, Inc., Vancouver, British Columbia, Canada) uses near-infrared laser light (Raman spectroscopy) to measure vibrational modes of biomolecules and distinguish malignant from benign skin lesions. The hardware includes a diode laser, a fibre and fibre-bundle delivery system, a hand-held Raman probe, a spectrograph, a camera detector, and a computer. A 785 nm laser beam is delivered to the probe, and the signal from the skin is transmitted to the spectrometer for spectral analysis.
MelaFind (MELA Sciences, Inc., Irvington, New York, US) uses an illuminator that shines light of 10 wavelengths, a lens system that creates images of the light scattered back from the lesions, and a light sensor to assess tissue up to 2.5 mm beneath the skin's surface. Information from the device is transmitted into image analysis algorithms using a skin disorder database. A treatment suggestion is provided; i.e., MelaFind positive (high degree of morphological disorganization) or MelaFind negative (low degree of morphological disorganization).
SIMSYS-MoleMate Skin Imaging System (MedX Health, Inc., Hamilton, Ontario, Canada) uses a hand-held scanner and computer software to provide images that demonstrate a lesion's vascular composition and pigment network. The technology employs spectrophotometric intracutaneous analysis (SIAscopy) — a light-based imaging system capable of producing rapid images of melanin, blood, and collagen to a skin depth of 2mm. The MoleMate proprietary software provides dermatoscopic images; dermal and epidermal pathological characteristics; and the ability to catalogue, monitor, and compare lesions over time.
Patient Group
The most common form of melanoma, encompassing 65% of melanomas, is superficial spreading melanoma, which often arises in a pre-existing mole and grows horizontally before invading vertically; a further 25% are nodular melanomas that bypass the horizontal growth phase.
Melanoma risk factors include severe blistering sunburn, ultraviolet light exposure (sunlight and tanning lamps or beds), presence of numerous moles (> 50), positive family or personal history, and immune suppression. Risk is higher for people with light- versus dark-coloured skin.
Compared to other cancers, a younger population is affected by melanoma, accounting for 22 years of lost life due to invasive disease. Unlike many cancers, the age-standardized incidence rates of melanoma have increased annually from 1998 to 2007 (by 1.4% in men and 1.5% in women) and the lifetime risk of developing invasive melanoma has increased from 1 in 500 people in 1930 to 1 in 74 in 2000.
Current Practice
Tumour depth is the most important prognostic factor for melanoma. Early detection when lesions are more superficial may improve survival; however, early recognition can be a challenge. Trained dermatologists can recognize advanced melanoma by visual inspection using the ABCDE criteria (Asymmetry, Border irregularity, Colour variegation, Diameter > 6 mm, Evolution), but, in the early stages, melanomas often mimic benign lesions.4 Hence, most melanomas in North America are >6mm in diameter (the size of a pencil eraser) when diagnosed.
For those at increased risk, such as people with many nevi (sharply circumscribed lesions of the skin) or a tendency to develop atypical nevi, early detection relies on thorough yearly examinations by physicians, supplemented by monthly self-exams by patients. There is no evidence to support general population screening for melanoma.
The reference standard for melanoma diagnosis is visual examination of skin lesions by a dermatologist, followed by biopsy and histopathology analysis, although inter-rater agreement among dermatopathologists is not 100%. For example, a study testing dermatopathologist agreement across 1,250 samples revealed a kappa value of 0.8 for melanoma versus non-melanoma and 0.62 for malignant versus borderline versus benign melanocytic lesions.
About half of all melanomas are first identified by the patient. Clinical guidelines suggest that a mole exhibiting a significant change in shape or colour, or causing itching or burning, should undergo complete (not partial) excision. This is possible if the lesion is small. If not — for example, for cosmetic or functional reasons — then incisional or punch biopsies are indicated focusing on areas with pigmentation variation or nodular components. Further, if a patient expresses concern about a particular lesion, it is recommended that reassurance be provided only if a lesion is highly unlikely to be melanoma; otherwise, repeat observation after one to two months is considered essential. Photography (single lesion or total body) may be used to capture baseline images with repeat photography several months later.
A useful dermatologic tool is dermoscopy, which involves 10x microscopy and polarized light and/or a liquid medium to allow for a non-invasive, detailed examination of the structures of a pigmented lesion.
Sequential dermoscopy may be used to track changes in lesions over time and has been shown to decrease rates of excision of benign lesions.38 However, the utility of dermoscopy varies with experience, many dermatologists are not trained in its use, and it can be time-consuming, particularly when used for multiple lesions.
Adverse Effects
No adverse effects of device use are described aside from the potential harms which may follow false-negative and false-positive results. False-negatives can lead to delays in diagnosis and treatment, and possibly increased morbidity and mortality, whereas false-positives can lead to unnecessary invasive procedures.
Sources:
https://www.asme.org/engineering-topics/articles/bioengineering/top-5-medical-technology-innovations
https://www.cadth.ca/optical-scanners-melanoma-detection