Impact of Cochlear Radiotherapy Dose on Hearing Loss in Carcinoma Oropharynx Treated by Concurrent Chemoradiotherapy Using Simultaneous Integrated Boost Volumetric Modulated Arc Therapy (SIB -VMAT)

This study evaluates the impact of reduction of radiotherapy dose received by cochlea on hearing loss in oropharyngeal cancer patients treated by concurrent cisplatin chemoradiotherapy using simultaneous Integrated Boost Volumetric Modulated Arc Therapy (SIB-VMAT). Sixty ears were evaluated in this prospective non blinded randomized trial. The study group (n=30) was treated with concurrent chemoradiotherapy using Image Guided Radiotherapy with Simultaneous Integrated Boost-Volumetric Modulated Arc technique. The matched control group (n=30) received concurrent chemoradiotherapy using 3D conformal radiotherapy (3DCRT). Concurrent chemotherapy was given to all patients with injection Cisplatinum 100 mg/m2 on D1,22&43 along with radiotherapy. Baseline hearing evaluation was done using puretone, impedence and high frequency audiometry. The tests were repeated at 6 months follow up to evaluate hearing loss. The mean radiotherapy dose received by the right and left cochlea in the 3DCRT and SIB-VMAT techniques was 38.99±4.78 versus 6.97±6.09 Gy (mean±SD) (p=0.001) and 38.59±5.10 versus 6.79±5.76 Gy (p=0.001). At 6 months of follow up sensorineural hearing loss was observed in 66.7 versus 0% (p=0.001) and 86.7 versus 6.7% (p=0.001) in the right and left ear in the 3DCRT and SIB-VMAT groups.High risk PTV 66 volume more than 300 cc was associated with a higher risk of hearing loss with odds ratio of 6.05 (95% CI 0.54-67.53) and 4.41(95% CI 0.52-37.16) in right and left ear. Age more than fifty years was associated with significant hearing loss in the right ear with an odds ratio of 12.56 (95% CI 0.84-187.87) (p=0.02) and 7.38 (95% CI 0.74-73.59) for the left ear. The study shows that reduction in radiotherapy dose received by cochlea is an independent determinant in reducing ototoxicity in the setting of concurrent single agent cisplatin chemotherapy. High risk PTV volume more than 300 cc was associated with a significant increase in hearing loss and PTV 66 volume emerged as a predictive factor for treatment related hearing loss.