Optimizing radiation therapy for merkel cell carcinoma: evaluating prognostic factors and treatment outcomes
July 25, 2025
Journal
International Journal of Clinical Oncology
Publication Date
July 25, 2025
Authors
Merkelcell.org Summary
Merkel cell carcinoma (MCC) is a rare but aggressive type of skin cancer. It is usually treated first with surgery and radiation therapy (RT), but the best way to use RT is still unclear. This study looked at 32 patients with MCC who were treated with RT to better understand which treatment factors might lead to better outcomes.
The average age of patients in this study was around 80 years old and they were followed for a little over two years after receiving RT. Many patients received both surgery and RT (23 patients). Among all the patients, 94% had their MCC controlled in the area where it started after two years. However, many people had recurrences outside of the RT area (~40%). 74% were still alive two years after RT.
The study found that among the patients that they analyzed, larger tumors (over 5 cm) were more difficult to treat effectively with radiation. Patients tended to have worse outcomes if they were male, didn’t have surgery along with radiation, were in poor overall health, or received radiation to a smaller area. Interestingly, the specific type or dose of radiation didn’t seem to make a big difference in results. However, it’s important to keep in mind that doctors may have chosen different treatment plans based on each patient’s other health problems, which could have affected the results.
In conclusion, RT works well to control MCC at the original site, but the cancer often still spreads beyond that. Using a larger RT treatment area and combining RT with surgery may help patients do better, although similar studies with more patients need to be done.
Full Publication
Background: Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine skin cancer. Surgery and radiation therapy (RT) are common treatment options; however, an optimal RT strategy has yet to be established. Therefore, the present study examined the outcomes of MCC patients treated with RT, with the aim of elucidating current RT practices and identifying prognostic factors for RT optimization.
Methods: This was a retrospective analysis of 32 non-metastatic MCC patients treated with RT. Local control (LC), progression-free survival (PFS), and overall survival (OS) rates were calculated using the Kaplan-Meier method. The Log-rank test was used to examine the effect of each factor on outcomes.
Results: Median age was 80 years, with a median follow-up period of 26 months. The median dose was 52 Gy in 26 fractions and combined with surgery in 23 patients. Two-year LC, PFS, and OS rates were 94, 61, and 74%, respectively. The Log-rank test showed that tumor size ≥ 5 cm was associated with worse LC (p = 0.03). Male sex and the absence of surgery correlated with worse PFS (p = 0.047 and 0.023, respectively). Performance status ≥ 2, the absence of surgery, and RT margin < 3 cm correlated with worse OS (p = 0.006, 0.02, and 0.02, respectively). RT dose, intensity-modulated RT, and elective nodal irradiation were not associated with any outcomes in this population.
Conclusion: RT achieved high local control; however, the metastasis rates were high. A wide RT margin and the combination of RT with surgery may improve the outcomes of MCC patients.
Keywords: Merkel cell carcinoma; prognostic factors; radiation therapy.