Evolution of postirradiated sudden deafness in nasopharyngeal carcinoma survivors during the past two decades.

OBJECTIVE/HYPOTHESIS: The beneficial effect of intensity-modulated radiotherapy (IMRT) on reducing the prevalence of postirradiated sudden deafness (PISD) in nasopharyngeal carcinoma (NPC) survivors has never been mentioned. This study investigated the evolution of PISD in NPC survivors during the past two decades.

STUDY DESIGN: Retrospective study.

METHODS: Of the 3,206 NPC patients who underwent radiotherapy during the past two decades, 32 patients (34 ears) had PISD. Twenty-nine patients (30 ears) received two-dimensional radiotherapy (2DRT) and were assigned to group A, whereas three patients (4 ears) undergoing IMRT were assigned to group B. An inner ear test battery including audiometry, vestibular-evoked myogenic potential (VEMP) test, and caloric test was performed for comparison between the two groups.

RESULTS: Group B (0.2%) showed significantly lower prevalence of PISD than group A (2%). Percentages of abnormal pursuit, saccade, and optokinetic nystagmus test results revealed nonsignificant difference between groups A and B. Likewise, both groups did not differ significantly in the percentages of abnormal pure tone average, cervical VEMP test, and caloric test. However, significant hearing improvement after treatment was identified in group B (P < 0.01) but not in group A (P > 0.05), probably because mean radiation dosage to the cochela of group B (35.0 ± 0.4 gray units [Gy]) was less than group A (50 ± 3 Gy).

CONCLUSION: Compared to 2DRT, both radiation dosages to the cochlea and radiation damage to tissues surrounding the inner ear are lessened by IMRT. Therefore, NPC survivors who received IMRT have a low prevalence of PISD, with significant hearing improvement after treatment.

LEVEL OF EVIDENCE: 4. Laryngoscope, 126:2016-2021, 2016.