Chemotherapy compliance in high-risk Merkel cell carcinoma treated with chemoradiotherapy

To evaluate chemotherapy (CT) compliance in patients treated with chemoradiotherapy (CRT) for high-risk Merkel cell cancer (MCC).

Data from three prospective clinical trials in high-risk MCC performed by the Trans-Tasman Radiation Oncology Group were included in this analysis. Patients were treated with one of two carboplatin-based CT schedules and standardised radiotherapy (RT) to the primary site and nodes to a dose of 50-60 Gy in 25-30 fractions. Patients' baseline characteristics were analysed using χ² tests to determine compliance factors for completing CT. A Cox univariate analysis was performed to assess the impact of CT compliance on time to locoregional failure, time-to-distant failure, time-to-recurrence and time-to-death.

A total of 88 patients were identified, with a median follow up of 38.5 months. Of these, 75 (85%) completed CT (median age 64.2 years, range 62.0-66.4), while 13 did not (median age 72 years, range 68.1-75.9), P = 0.006. Women comprised 18/75 patients who completed CT and 7/13 patients who did not complete it (P = 0.03). Performance status, site, stage, surgical margins, RT dose and toxicity did not impact on their CT compliance. At 5 years, 26% of patients had locoregional relapse, 26% had distant failure and 34% had died.

In this small cohort of patients treated with CRT for high-risk MCC, older age and female sex were associated with failure to complete CT. Severe acute skin and haematological toxicity did not correlate with failure to complete CT.