Trial of a deep laser technique to prevent skin cancers in people with a strong history of them.

Study participants aged 45 years or older with a history of more than 10 epidermal carcinomas will be considered. Patients will be excluded if they have used field therapy such as topical fluorouracil, photodynamic therapy, ingenol or imiquimod on the areas considered for treatment in the past 6 months; if they have had an organ transplantation or are on immunosuppressive therapy; if they have an active blood borne disease (e.g. HIV) or have a hereditary genetic condition favoring a skin cancer. Dorsal forearms are used as they are often severely sun-exposed areas. ND-YAG ablative laser resurfacing will be conducted on the identified area under local anesthesia in the department of dermatology at the Princess Alexandra Hospital, Brisbane, by a dermatological surgeon. This method is preferred to dermabrasion as it is easier to control the depth and has a greater safety profile. Laser parameters include: wavelength of 2940nm, frequency of 8hz, 4-6 passes at different depths (equivalent to a depth of ablation 400 microns and 600 microns), overlap of 50%, dose is 25J/cm2 per pass. There is no cooling. In consenting patients and using a marker pen, three areas of skin, each measuring 25mm x 25mm (about the size of a ten cent piece) will be selected. These regions will not have any skin cancers on them. Two of these areas will be resurfaced and one will act as a control area. Two of the areas will then be injected with local anaesthetic. When the skin is numb both areas will be lasered, one to a depth of 0.4mm and the other to 0.6mm. This compares to the thickness of 1-2 business cards. This ‘resurfacing’ will remove the sun-damaged skin layers. The third area will not be treated and will be used as a control area. After 3 months, 2mm (diameter) biopsies will be taken from the resurfaced and the control areas. A saliva specimen will be used for reference genomic DNA. Whole exome sequencing will be conducted at 500X depth.