Delayed lower cranial neuropathy after oropharyngeal intensity-modulated radiotherapy: A cohort analysis and literature review

Background: The purpose of this study was to examine swallowing-related lower cranial nerve palsy (LCNP) in oropharyngeal cancer (OPC) survivors after intensity-modulated radiotherapy (IMRT). Methods: Patients treated with definitive IMRT (66-72 Gy) were pooled from institutional trial databases. Prospective analyses on parent trials included videofluoroscopy, clinical LCNP examination, and questionnaires pre-IMRT, 6 months post-IMRT, 12 months post-IMRT, and 24 months post-IMRT. Time-to-event and incidence of LCNP was estimated with competing risk methods. Literature review (1977-2015) summarized published LCNP outcomes. Results: Three of 59 oropharyngeal cancer survivors with a minimum 2-year follow-up developed hypoglossal palsy ipsilateral to the index tumor (median latency 6.7 years; range 4.6-7.6 years). At a median of 5.7 years, cumulative incidence of LCNP was 5%. LCNP preceded progressive dysphagia in all cases. Published studies found median incidence of radiation-associated LCNP was 10.5% after NPC, but no OPC cancer-specific estimate. Conclusion: Although uncommon, the potential for late LCNP preceding swallowing deterioration highlights the importance of long-term functional surveillance in OPC survivorship.