Natural history of high-risk cutaneous primary melanoma and risk factors for disease progression

Abstract

Background: Melanoma is a potentially fatal cancer of the skin that is associated with high disease burden in Australia. Exposure to ultraviolet radiation is the most important environmental risk factor. When diagnosed early, primary melanoma is curable, however melanomas greater than 1mm in thickness and those with ulceration have a high risk of recurrence and metastases, and little is known about factors influencing their progression.Aims: The primary aim was to describe the natural history of localised high-risk primary melanomas after treatment, for up to 2 years post-diagnosis and to identify risk factors for disease progression. My two secondary aims were to investigate patients' use of health services, and explore sun protection behaviours and risk of subsequent primary melanoma.Methods: This project was conducted among a cohort of patients who had newly-diagnosed primary melanoma (tumour stage T1b-T4b) treated in Queensland, 2010 to 2014. Melanomas were histologically confirmed, and patients completed questionnaires at baseline and at regular intervals thereafter. Statistical techniques, including survival analyses, regression models and latent class analyses were used to answer the research questions.Results: Amongst 700 patients with high-risk primary melanoma, 94 (13%) developed a recurrence within 2 years. Most first recurrences occurred at local or regional sites, whereas subsequent recurrences were more common at distant sites. Higher risk of melanoma recurrence was observed with increasing tumour thickness, tumour ulceration, mitotic rate >3/mm 2 and head or neck location of primary. Ulcerated tumours occurred more commonly in patients with diabetes, whereas patients regularly taking statins had a lower likelihood of an ulcerated tumour. Long-term statin users, especially male users, also had a lower risk of melanoma recurrence. Secondary outcomes demonstrated that patients with inadequate sun protection behaviour after melanoma diagnosis were at higher risk of developing a subsequent