Impact of adjuvant radiation therapy on survival and recurrence in patients with stage I-III Merkel cell carcinoma: a retrospective study of 312 patients

Merkelcell.org Summary

This study performed in France examined how adding radiation treatment may affect the chance of MCC recurrence. The study focused on patients whose cancer was limited to a local site or had spread to nearby areas like lymph nodes, but not distant parts of the body. Some patients only had surgery, while others had surgery and then radiation therapy (“adjuvant radiation”). The results showed that patients who received the additional radiation after surgery stayed disease-free for longer, with 48% less risk of the cancer returning in the same place or near the surgery site. However, it must be noted that the radiation did not seem to reduce the risk of recurrence in other parts of the body outside of radiation treated area. This study suggests that getting additional radiation after surgery (adjuvant radiation) for MCC may be beneficial in preventing recurrences, which supports prior studies.

Abstract

The therapeutic recommendations for American Joint Committee on Cancer I-III stage Merkel cell carcinoma (MCC) include surgery and adjuvant radiation therapy (aRT) on the tumoral bed, along with lymph node (LN) dissection and/or aRT of LN area in case of regional disease. However, the impact of aRT on outcomes remains controversial. In a previously reported cohort of French patients with MCC, we retrospectively compared outcomes in 86 patients who had undergone only surgery versus those in 226 patients who had undergone surgery and aRT . Detailed procedures (type of surgery and site of aRT) are described in Supplementary Table I (available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). The median time between surgery and aRT was 8.5 weeks. Patients who had received aRT were significantly younger (P = .001) and had more frequently undergone sentinel lymph node biopsy (SLNB) (P = .002) than those from the surgery-only group (Table I). When taking into account all types of recurrences, patients who had received aRT had significantly longer recurrence-free survival (RFS) (P < .0001) than those from the surgery-only group (Supplementary Fig 1, A, available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). On multivariate analysis, aRT was independently associated with a reduced risk of disease recurrence (hazard ratio [HR], 0.48; 95% CI, 0.00-0.78) (Supplementary Table II, available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). When focusing on the pattern of recurrence, patients who had received aRT had significantly increased local RFS (P < .0001) and regional LN RFS (P < .0001) than those from the surgery-only group, but there was no impact of aRT on in-transit RFS (P = .11) and distant metastasis–free survival (P = .15) (Supplementary Fig 1, available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). On multivariate analysis, aRT remained significantly associated with a reduced risk of local (HR, 0.01; 95% CI, 0.00-0.10) and regional LN recurrence (HR, 0.46; 95% CI, 0.00-0.82) (Supplementary Table III, available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). Patients who had received aRT had significantly longer disease-specific survival (DSS) (P = .01) (Fig 1). On multivariate analysis, aRT was independently associated with a reduced risk of death due to MCC (HR, 0.47; 95% CI, 0.00-0.89) (Supplementary Table II, available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1). The pattern of recurrence according to the site of aRT and nodal status at baseline are provided in Supplementary Tables IV and V (available via Mendeley at https://doi.org/10.17632/mgfk4npkr6.1).