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. Key words: Nasopharyngeal cancer; Recurrence; Re-irradiation; Carbon-ion radiation therapy; Intensity-modulated radiation therapy