Abstract Background Rhabdomyosarcoma is the most common soft tissue sarcoma in children, but rare in adults. Para-meningeal rhabdomyosarcoma in head and neck (PM-HNRMS) is less applicable for surgery due to the anatomic reason. PM-HNRMS has a poor prognosis in children. However, its clinical outcomes remain unclear in adults due to the rarity. Further, there is almost no detailed data about salvage therapy. Methods We retrospectively examined the adult patients with PM-HNRMS treated at institutions belonging to the Kyushu Medical Oncology Group from 2009 to 2022. We evaluated the overall survival (OS) and progression-free survival (PFS) of the patients who received a first-line therapy. We also reviewed the clinical outcomes of patients who progressed against a first-line therapy and received salvage therapy. Results Total 11 patients of PM-HNRMS received a first-line therapy. The characteristics were as follows: median age: 38 years (range 25 – 63 years), histology (alveolar/spindle): 10/1, and risk group (intermediate/high): 7/4. As a first-line therapy, VAC and ARST0431-based regimen was performed in 10 and 1 patients, respectively. During a first-line therapy, definitive radiation for all lesions were performed in seven patients. The median PFS was 14.2 months (95%CI: 6.0 – 25.8 months): 17.1 months (95%CI: 6.0 – not reached (NR)) for patients with stage I-III and 8.5 months (95%CI: 5.2 – 25.8 months) for patients with stage IV. The 1-year and 3-year PFS rates were 54.5% and 11.3% for all patients. Median OS in all patients was 40.8 months (95%CI: 12.1 months–NR): 40.8 months (95%CI: 12.1 – NR) for patients with stage I-III and NR for patients with stage IV. The 5-year OS rate was 48.5% for all patients. Among seven patients who received salvage therapy, three are still alive, two of whom remain disease-free for over 4 years after completion of the last therapy. Those two patients received multi-modal therapy including local therapy for all detected lesions. Conclusion The cure rate of adult PM-HNRMS is low in spite of a first-line therapy in this study. Salvage therapy might prolong the survival in patients who received the multi-modal therapy including local therapy for all detected lesions.
