NIR and Skin Cancer Margins

Non-melanoma skin cancer (NMSC) is the most common cancer diagnosis in Canada, and its incidence is still increasing. Visual examination followed by biopsies of suspicious lesions are the gold standard for skin cancer diagnosis. The mainstays of treatment include photodynamic therapy, radiation therapy, and surgical excision. The margins of NMSC lesions are typically determined via visual inspection, and excised based on delineating normal from abnormal tissue. According to the National Comprehensive Cancer Network, low-risk basal cell cancers should be excised with a 4mm margin; squamous cell skin cancers and high-risk basal cell cancers should be excised with 4-6mm margins, as per the National Comprehensive Cancer Network. These lesions frequently occur on cosmetically sensitive areas of the head and neck, therefore accurate margins and excision can help to preserve the overall appearance. Accurate lesion delineation with proper margins can also reduce the need for further treatment if the margins are positive. In approximately 2-3% of cases at our centre, the margins are positive.

Near-infrared radiation (NIR) represents the light spectrum from 0.7 to 1.5 micrometers. At the shorter wavelengths, it merges with the red spectrum of visible light. These forms of light have the ability to heat the skin up to a 5 mm depth. Previous studies have examined the relationship between skin blood flow and temperature when heating skin, where dermal temperature can reach a certain peak in a defined time. Other studies have investigated the application of NIR when combined with photo immunotherapy, as a means of treating other cancers. More elaborate multispectral analysis devices have been studied for their effectiveness in diagnosing cutaneous malignancies. NIR application is well tolerated, in past studies.The objective of this study is to determine if the vasculature of normal skin and NMSC skin appears differently following heating with NIR light, and if this difference corresponds to better margin delineation.

The excisions and reconstructions are all within the standard of care. The only added testing will be application of near-infrared heat via a heating lamp to the lesional skin, for a total of ten minutes. Each patient will have their skin cancer lesion photographed, and traced onto acetate film. The NIR heating will then occur under a lamp for a total of ten minutes at a distance of 20cm. At the end of the ten minutes, the lesion and its borders will again be traced onto a separate acetate film. Using Excel for block randomization, patients will then be randomized to excision with the non-heated versus heated margins. The allocation will not be known until the moment of assignment. The excisions will then occur in the same fashion between the two groups, and all specimens will be submitted for pathology, as is standard of care.

Data will be recorded for various patient and lesions factors that may potentially influence the outcome of NIR heating therapy. These include age and gender, lesion size and location, and history of skin disorders. The lesion size and final pathology, with quantitative margin distances, will be recorded. Statistical analysis will be performed to determine if there is an overall difference in qualitative (negative or positive) and quantitative margin status between those lesions excised under standard procedure vs. NIR heating.