A Single-Fraction Radiation Therapy Multi-Site Study
The MC3 Institute is planning to evaluate the efficacy of postoperative Single-Fraction Radiation Therapy (SFRT) compared to 5-week conventional Radiation Therapy (cRT) and observation groups for Stage I-II MCC patients at low-to-moderate risk of recurrence.
BACKGROUND
As a radiation-sensitive cancer, MCC is primarily treated with surgery and/or radiation therapy when locally confined. The current 2025 National Comprehensive Cancer Network (NCCN) guidelines recommend a 5-week cRT course (~50 Gray (Gy) in 25 fractions) for those who have risk factors. However, cRT can have significant side effects such as delayed would healing, lymphedema and less commonly, osteoradionecrosis, and radiotherapy-induced sarcoma. Furthermore, the need to travel every day during a 5-week course can mean that adjuvant radiation is not an option for older patients who live far from the treatment center.
In palliative settings, a single fraction of radiotherapy at 8 Gy has shown a high in-field control rate of 94% with minimal toxicity[1]. In the adjuvant setting, our preliminary single-center data indicate that 8 Gy SFRT achieved 100% local control (n=43), significantly better than observation (91.5%, n=111, p=0.028), in patients with local Stage I-II MCC[2]. This SFRT approach was not only more convenient but also led to markedly fewer side effects. Indeed, 82% of patients who received the 8 Gy SFRT noted no side effects. This one-time treatment has allowed a higher number of patients to benefit from adjuvant RT while lowering costs and minimizing toxicities.
PROPOSAL
Prior to potentially broader adoption, we believe it is essential to assess and validate the safety and efficacy of 8 Gy SFRT across multiple centers. MC3 will serve as the coordinating site of this multi-site study.
We want to identify other centers that are interested in contributing data such as baseline risk factors and long-term outcome data for MCC patients with local-only MCC who undergo adjuvant SFRT, cRT, or observation.
If you would like to join us as a participating center, please contact us at mc3institute@uw.edu. We will invite you to join our planning process.
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Iyer JG, Parvathaneni U, Gooley T et al. Single-fraction radiation therapy in patients with metastatic Merkel cell carcinoma. Cancer Medicine 2015; 4: 1161-70. https://onlinelibrary.wiley.com/doi/10.1002/cam4.458
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Huynh ET et al. A single postoperative dose of radiotherapy (8 Gy) has comparable efficacy to a standard 5-week course for localized Merkel cell carcinoma (MCC). Journal of Investigative Dermatology 2024,Volume 144, Issue 8, S160https://www.jidonline.org/article/S0022-202X(24)01543-4/fulltext
