Early results of carbon-ion radiation therapy in the treatment of locally recurrent nasopharyngeal carcinoma

Objective: To compare the short-term outcomes with regards to efficacy and toxicity after reirradiation using intensity-modulated carbon-ion radiotherapy (IMCT) or intensity-modulated radiation therapy (re-IMXT) in nasopharyngeal cancer (NPC) patients who developed local recurrence (LRNPC) after their initial, definitive IMXT course. Methods: The short-term outcomes of 14 patients retreated for LRNPC between May of 2015 and September of 2015, who were followed-up for at least 3 months after salvage IMCT, were compared to those of 47 similar patients retreated with repeat IMXT between 2012 and 2014. Dose of salvage IMCT and re-IMXT were 50-60 GyE (2.0-2.5 GyE/d) and 54-66 Gy (2.0-2.1 Gy/d), respectively. Results: The characteristics of the patients and disease including:patients' gender, age, stage at initial diagnosis, time interval between the initial IMXT and local recurrence, dose of initial IMXT, and the use of chemotherapy during initial treatment, and N-classification at recurrence were similar between the 2 groups. Complete response rates at 3-month follow-up were 64.3% vs. 78.7% between the salvaging IMCT and re-IMXT groups, respectively (P > 0.05). No patients developed local disease progression in either group within 6-month follow-up, but 2 patients died after re-IMXT including 1 from massive nasopharyngeal hemorrhage. The probability of acute mucositis (31.9% vs. 0, P < 0.05) and mucosal necrosis/hemorrhage (29.8% vs. 0, P < 0.05) were significantly higher in patients who received re-IMXT as compared to those who received salvage IMCT. In addition, 2 patients developed symptomatic temporal lobe necrosis after re-IMXT, while none developed this in the IMCT group. No patients developed cranial nerve palsy. Conclusions: When locally recurrent NPC after primary definitive IMXT is retreated with either IMCT or IMXT, similar response rates and overall survival times within 6 months after re-irradiation are observed. However, no patient who received salvage IMCT developed acute or subacute toxicities of grade 2 or above, whereas 29.8% patients experienced life-threatening mucosal necrosis/hemorrhage after re-IMXT. The long-term outcome of salvage IMCT in LRNPC needs further follow-up. (authors)