DELAYS in beginning post-operative radiation therapy (PORT) can increase the risk of recurrence of Merkel cell carcinoma (MCC), the second most deadly form of skin cancer, according to a recent study from the University of Washington, Seattle, USA. Researchers found that locoregional recurrence of MCC after 5 years significantly increased if it took longer than 8 weeks for PORT to begin.
This retrospective study evaluated the association between the time to initiate PORT and locoregional recurrence of MCC, using competing risk regression in patients with early stage MCC. Metastasis and death were used as competing risks.
The study found that the median time to start PORT was 41 days (range: 8–125 days), with a median follow-up time of 55 months. Of the 124 patients included in the study, 17 (14%) developed locoregional recurrence of MCC. Of those patients, 14 (82%) had locoregional recurrence occur outside of the radiation field. Locoregional recurrence at 5 years increased when time to initiate PORT was over 8 weeks versus under 8 weeks (28% and 9.2%, respectively; p=0.06). Risk for locoregional recurrence increased by up to 20% for every additional week that it took to begin PORT (p=0.002). Lastly, the cumulative incidence of MCC-related deaths was also associated with the delay in initiating PORT, with a hazard ratio of 1.14 per extra week (p=0.16).
Although this research needs to be repeated on a larger scale to improve multivariable analyses, it shows promise in establishing the optimum time to begin radiation therapy following MCC surgery, which was previously unknown. Authors of the study say the data suggests that “PORT should be initiated as early as feasible, ideally within 8 weeks of definitive surgery.”
