Incidence, Pattern And Predictive Factors For Hypoglossal Nerve Palsy After Definitive Intensity-Modulated Radiation Therapy (Imrt) For Nasopharyngeal Carcinoma (Npc)

Hypoglossal nerve palsy is the most common cranial nerve dysfunction after definitive radiotherapy for nasopharyngeal cancer (NPC), which risk is poorly characterized in the contemporary intensity-modulated radiotherapy (IMRT) era. This study aimed to evaluate its incidence, pattern and predictive factors in a large single-institutional cohort. Case records of 836 consecutive non-metastatic NPC patients who underwent definitive IMRT between February 2003 and December 2011 were reviewed. Cumulative incidence, etiologies and time to dysfunction of post-treatment hypoglossal nerve palsies were evaluated. Predictive factors for the development of nerve palsies were analyzed using the Cox proportional hazard model. The association with aspiration pneumonia was analyzed using Pearson's Chi-square test. The median follow-up was 7.9 years. After excluding 27 patients with <6 months follow-up and 1 patient with history of tongue resection, 808 patients were eligible for analysis. Eighty-seven patients developed hypoglossal nerve palsies (10.8%), 61 were unilateral and 26 were bilateral. The 3-year, 5-year and 8-year cumulative incidences were 0.8%, 2.8% and 8.2% respectively. Eighty-four percent (73/87) of the palsies were radiation-induced, 16% (14/87) were due to tumor recurrence. Median time to nerve palsy was significantly longer among radiation-induced versus recurrence group (6.1 years vs 3.5 years, p=0.025). Use of chemotherapy, history of re-irradiation, co-existing diabetes and connective tissue diseases were independent risk factors for radiation-induced nerve palsies. Patients with hypoglossal nerve palsies had higher risk of aspiration pneumonia which required hospitalization (27.3% vs 9.2%, p<0.001). High incidence of hypoglossal nerve palsy was observed after definitive IMRT for NPC, most of which were as a result of radiation toxicity. Further dosimetric and quality-of-life analyses are warranted for this late debilitating complication.