Increased risk of recurrence and disease-specific death following delayed post-operative radiation for Merkel cell carcinoma
October 18, 2023
Journal of the American Academy of Dermatology
October 18, 2023
For MCC patients who have local disease, the standard treatment course is surgery followed by radiation therapy. However, it is not known how quickly surgery should be followed by radiation, and there are often delays in radiation treatment due to surgical wound healing and logistics. The authors analyzed the time interval between surgery and radiation therapy among 125 MCC patients with local disease. They found that patients whose radiation was delayed more than 8 weeks after surgery had a significantly increased risk of having a recurrence and dying from MCC. They hypothesized that delaying radiation after surgery could allow MCC cells near the surgical site to spread and lead to recurrences. This study supports the importance of patients receiving radiation within 8 weeks from their surgery date.
Background: Merkel cell carcinoma (MCC) is often treated with surgery and post-operative radiation therapy (PORT). The optimal time to initiate PORT (ttPORT) is unknown.
Purpose: We assessed if delays in ttPORT were associated with inferior outcomes.
Methods: Competing risk regression was used to evaluate associations between ttPORT and locoregional recurrence (LRR) for patients with stage I/II MCC in a prospective registry and adjust for covariates. Distant metastasis and death were competing risks.
Results: The cohort included 124 patients with median ttPORT of 41 days [range: 8-125 days]. Median follow-up was 55 months. 17 (14%) patients experienced a LRR, 14 (82%) of which arose outside the radiation field. LRR at 5 years was increased for ttPORT >8 weeks vs <= 8 weeks, 28.0% vs 9.2%, p=0.006. There was an increase in the cumulative incidence of MCC-specific death with increasing ttPORT (HR=1.14 per 1-week increase, p=0.016).
Limitations: The relatively low number of LRRs limited the extent of our multivariable analyses.
Conclusions: Delay of PORT was associated with increased LRR, usually beyond the radiation field. This is consistent with the tendency of MCC to spread quickly via lymphatics. Initiation of PORT within 8 weeks was associated with improved locoregional control and MCC-specific survival.