Carbon-ion radiotherapy in the treatment of radiation-induced second primary malignancies

BACKGROUND: Treatment of radiation-induced second primary malignancy (RI-SPM) is challenging and usually associated with poor outcomes. For patients with unresectable or incompletely resected diseases, carbon-ion radiotherapy (CIRT) offers physical and biologic advantages over photon-based re-irradiation. We report the results of salvage CIRT in 15 patients with RI-SPM. METHODS: Fifteen consecutive and non-selected patients with RI-SPM who underwent salvage CIRT at the Shanghai Proton and Heavy Ion Center between November 2015 and May 2019 were included in this retrospective study. CIRT doses were 57.5–69 Gy (RBE) [at 2.5–3.0 Gy (RBE)/daily fraction]. The actuarial 1-year overall survival (OS), locoregional progression-free survival (LPFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS) rates as well as acute/late toxicities were analyzed. RESULTS: Among the 15 patients included, 10 were soft tissue sarcomas, 2 were chondrosarcomas, 1 was osteosarcoma, 1 was squamous cell carcinoma and 1 was esthesioneuroblastoma. With a median follow-up of 13.0 (range, 2.73–29.63) months, the actuarial 1-year OS, LPFS, DMFS, and PFS rates were 69.3%, 53.0%, 92.9%, and 48.2%, respectively. No grade 2 and grade 3 acute adverse effect was observed. One patient experienced grade 4 hemorrhage which required embolization during CIRT, and lately died from hemorrhage (grade 5) at 3.4 months after the completion of CIRT. No other late adverse effects of ≥ grade 2 was observed. CONCLUSIONS: Salvage CIRT provided relatively safe and effective short-term outcome for patients with unresectable or in-completely resected RI-SPM, as compared to historical data on re-irradiation using the conventional photon beam technology. However, further improvement in both disease control and toxicity prevention is needed.