Chemo-radiation to the inner ear may lead to sensorineural hearing loss (SNHL). However the relative contribution to SNHL from RT alone, chemo radiation, and the dose–effect relationship for radiation with or without cisplatin-based chemotherapy remain undefined in the literature, but the severity of damage increases with dose. Study was done to quantify the severity of SNHL produced after concurrent chemo irradiation in patients of head and neck cancer and assess the effect of dose reduction to cochlea with VMAT.
Pre-treatment and post-treatment audiograms for 31 patients who received combined modality therapy were analysed. Doses prescribed were 68.2 Gy at 2.2 Gy/fraction to gross tumour volume. Locally advanced disease patients received 2 cycles of three weekly cisplatin regimen. Radiation was delivered by VMAT technique. Hearing changes were assessed by comparing the mean threshold values of the baseline audiogram to the corresponding values of the most recent follow-up audiogram. SNHL was defined as ≥20 dB increase in bone conduction threshold at one frequency or ≥10 dB increase at two consecutive frequencies.
The mean audiogram follow-up time was 8 months (range 2-14 months). 2 patients required dose reduction due to altered renal parameters. The mean radiation dose to the cochlea was 1070 cGy (range 290-3947 cGy). Nine of 31 patients (30%) developed significant sensorineural hearing loss at 8000 Hz with a mean threshold increase of 22.6 dB (CI 10.6 - 37.6 dB) at months follow. The mean cochlea dose for these patients was 27Gy (range 15Gy - 34Gy). For patients only receiving RT, no significant hearing loss was found even at 40 Gy. About half (46%) of the patients who received cisplatin with mean cochlea dose of <8Gy had no documented audiogram abnormalities.
High frequency SNHL was observed in one third of patients who received both concomitant cisplatin and radiotherapy even at expected tolerable doses (mean cochlea dose was 27Gy). Hence optimization of radiation doses using VMAT could spare the inner ear from cumulative toxicities of chemotherapy and reducing dose to 1.8Gy/fraction to cochlea using SIB, late effects can be reduced.
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All authors have declared no conflicts of interest.