The epidemiology of multiple primary melanomas in Australia

Abstract

Melanoma is a serious form of skin cancer and Australia (with New Zealand) has the highest incidence of melanoma in the world, and increasing rates among older generations. Overall survival rates after a diagnosis of melanoma are relatively high, which leads to many people living with a previous melanoma diagnosis. Compared to the general population, melanoma survivors are at a much higher risk of developing a subsequent primary melanoma and require ongoing skin surveillance. However, most epidemiological research has focused on the first melanoma diagnosis. The objective of my PhD was to contribute new insights to the understanding of the epidemiology of multiple primary melanomas in Australia. We aspire for these findings to be applicable to broader melanoma populations through replication and validation in further research.

This thesis comprises four quantitative studies that focused on investigating the survival rates, risk factors for occurrence, and incidence trends of multiple primary melanomas. Chapter 2 evaluated absolute risk and potential risk factors of developing a second primary melanoma. The results indicated that male sex, older age, high naevus count and body site are risk factors associated with higher risk of second primary melanoma. Chapter 3 investigated risk factors of developing a second primary melanoma or other types of cancers after the initial melanoma diagnosis, indicating the most common second cancers were melanoma, followed by prostate cancer, breast cancer and colon cancer. Chapter 4 evaluated the trends in the incidence rate of second primary melanomas in Australia, finding out the incidence rates increased by 3 to 5-fold over three decades. Chapter 5 investigated whether there are survival variations between people diagnosed with single and multiple primary melanomas, and the result draws a conclusion that the number of melanomas is not an independent risk factor for prognosis.