Hypofractionated versus standard fractionation radiotherapy for Merkel cell carcinoma

Merkelcell.org Summary

Radiation therapy is a common treatment for Merkel cell carcinoma (MCC) because this type of cancer responds well to radiation. Typically, patients get daily doses of about 2 Gray (a Gray, Gy, is a measure of how much energy is used) each day. Over daily treatments during 4-6 weeks, a total of 50-60 Gy is given. This study looks at a different type of radiation treatment called hypofractionated radiation, which uses higher doses (4 or 8 Gy) in only 1-3 treatments, for a total of 8-24Gy, making it more convenient for patients. The study compared radiation treatments for MCC given to 29 patients—13 got standard radiation, and 16 got hypofractionated radiation. They found that none of the patients who received standard radiation had their cancer return in the treated area within 10 months, compared to one patient in the hypofractionated group. This suggests that both methods are similarly effective in preventing MCC from coming back in the treated area. They also found no major differences in survival between the two groups. It is also important to note that radiation therapy can often cause side effects, including severe burn-like skin injuries, chronic wounds, or bone damage. In this study, none of the patients who got hypofractionated radiation had severe side effects, while 30% of those who got standard radiation did. Although this study had a small number of patients, it suggests that hypofractionated radiation might work as well as standard radiation for MCC, with fewer side effects and more convenience.

Abstract

Purpose/Objective(s)
Merkel cell carcinoma (MCC) radiation treatment has historically consisted of standard 1.8–2 Gy fractions treated daily over 4–6 weeks. Hypofractionated treatment regimens have demonstrated tumor control and toxicity equivalence to standard fractionation regimens for common cutaneous malignancies such as basal cell and squamous cell carcinomas. Herein we report the outcomes of hypofractionated versus standard fractionation radiotherapy for MCC at our institution.

Materials/Methods
The study involved a retrospective review of MCC patients treated with radiotherapy. Treatment characteristics and patient outcomes, including acute toxicities, disease recurrence and survival data were collected. The cumulative incidence of local and distant failures was estimated, with death as a competing risk.

Results
A total of 29 treatment courses for 24 patients were included, of which 13 involved standard fractionation with curative intent, 10 involved hypofractionated radiotherapy with curative intent, and 6 involved single fraction (8 Gy) palliative radiation. Half the patients were treated to a head/neck site. A subset of patients treated adjuvantly with curative intent included 8 standard fractionation and 8 hypofractionated radiotherapy patients. No statistically significant differences in local and/or distant failure or overall survival was observed between the patient groups.

Conclusion
Hypofractionated radiotherapy for MCC was associated with similar treatment outcomes relative to standard fractionation. In our limited patient sample, hypofractionated radiation treatment achieved similar results with similar toxicity and fewer treatments. Further analysis of a larger patient population with longer follow up is needed to confirm treatment tolerability and efficacy.

Keywords: Merkel cell carcinoma, Hypofractionation, Radiation Therapy