Merkel cell carcinoma: a forty-year experience at the Peter MacCallum Cancer Centre
January 9, 2023
January 9, 2023
This study from Australia provides useful insight on the outcomes of more than 500 Merkel cell carcinoma patients in a place that relies heavily on radiation therapy. The risk of recurrence is very similar to what we see in the US and thus provides more confidence in current US-based data. This study also provides insigh into the highly controversial topic of radiation and “surgical margins”. The authors found that even if the surgical margins were positive, if patients received radiation to the primary site, outcomes were excellent. This suggests that taking large surgical margins is not required if radiation is to be given. Moreover, if extensive surgery delays radiation, this is likely not in the patient’s best interest.
Merkel cell carcinoma (MCC) is a rare but highly aggressive neuroendocrine skin malignancy, with Australia having the highest reported incidence in the world. There is currently a lack of consensus regarding optimal management of this disease.
This was a retrospective audit conducted by reviewing existing medical records of MCC patients presenting to the Peter MacCallum Cancer Centre (PMCC) between 1980 and 2018. The primary endpoint was locoregional recurrence. The secondary endpoints were distant recurrence, disease-free survival (DFS) and overall survival (OS).
A total of 533 patients were identified. Locoregional recurrence occurring at one, two and 5 years was 24, 31 and 32%, respectively. The estimated 5-year OS and DFS were 46% (95% Confidence Interval [CI] 41–51%) and 34% (95% CI 30–39%) respectively. Older age at diagnosis (hazard ratio [HR] per year = 1.07, 95% CI 1.06–1.07, p < 0.001), and larger primary tumour diameter (HR =1.16, 95% CI 1.03–1.31, p = 0.019) were associated with worse OS on multivariable analysis. Positive or negative histopathological margin status was not associated with OS or DFS differences in patients treated with post-operative radiotherapy.
In our study, about a third of patients developed locoregional recurrence, distal recurrence or both, and there appears to be no change over the last four decades. If treated with adjuvant radiotherapy, there is no difference in OS or DFS with positive surgical margins. Findings should influence future guidelines.