Aims: Queensland has the highest incidence of Merkel cell carcinoma (MCC) in Australia with a rate of 2.2 per 100,000. MCC is a rare, highly aggressive skin cancer with a high risk of spreading if not diagnosed early. This analysis aims to describe the epidemiology of MCC in Queensland and examine variations in diagnosis, treatment, recurrence and survival.
Methods: This retrospective population-based analysis used data from the Queensland Oncology Repository (QOR). A comprehensive review was undertaken, and specific pathological information was collected for people diagnosed with MCC from 2012 to 2021. Follow up time was up to 31st December 2022. Kaplan-Meier method was used to calculate survival and recurrence.
Results: Of the 1064 people diagnosed with MCC over the ten years, 68% were male, 1% were First Nations peoples, and the median age at diagnosis was 78 years (range 26-105). The most common primary locations were the face, ears and neck accounting for 42% of cases. Approximately 30% with a known stage at diagnosis had an advanced tumour stage. Radiation therapy (RT) treatment utilisation for all MCC cases was 58%. The median time for MCC-specific survival was 40 months; and the 5-year survival rate improved from 39% (95% CI, 35–44%) to 46% (95% CI, 41–52%) between 2012-2016 and 2017-2021. Factors associated with death included increasing age, higher comorbidity burden and advanced stage (all p <0.001). Approximately one-third of the cases experienced a recurrence, with the median time to recurrence being 16 months.
Conclusion: While MCC is a rare skin cancer, incidence in Queensland is high. Encouragingly, survival is improving due to advances in histological diagnostic techniques and treatments. Age, comorbidity burden and advanced stage were all predictors of poorer survival. Further analysis will be conducted to examine influences of overall stage and the use of immunotherapy therapies.