Failure patterns and individualized treatment plans of reirradiation for inoperable locally recurrent nasopharyngeal carcinoma.

Re-irradiation with intensity-modulated radiotherapy (IMRT) remains the primary treatment modality for inoperable locally recurrent nasopharyngeal carcinoma (NPC). However, the rate of radiation-related late adverse effects is often substantially high. Therefore, we aimed to explore failure patterns and individualized treatment plans of re-irradiation for inoperable locally recurrent NPC. Ninety-seven patients who underwent IMRT were retrospectively analyzed. Sixty-two patients had clinical target volume of recurrence (rCTV) delineated, and thirty-five patients had only gross tumor volume of recurrence (rGTV) delineated. Twenty-nine patients developed second local failures after re-irradiation with IMRT (28 cases available). Among those patients, 64.3% (18/28) of patients and 35.7% (10/28) developed in-field or out-field, respectively. No statistical correlation was observed between target volume (rGTV or rCTV) and the local recurrence rate, local failure patterns, grade ≥ 3 toxicity, and survival. Multivariate analysis showed that recurrent T (rT) stage (HR 2.62, P = 0.019) and rGTV volume (HR 1.73, P = 0.037) were independent prognostic factors for overall survival (OS). Risk stratification based on rT stage and rGTV volume revealed that low risk group had a longer 3-year OS rate (66.7% vs. 23.4%), lower total grade ≥ 3 toxicity (P = 0.004), and lower re-radiation associated mortality rates (HR 0.45, P = 0.03) than high risk group. This study demonstrates that the delineation of rCTV may not be beneficial for re-irradiation using IMRT in locally recurrent NPC. Patients with low risk were most suitable for re-irradiation, with maximizing local salvage and minimizing radiation-related toxicities. More precise and individualized plans of re-irradiation are warranted.