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

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.

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.

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.

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.