Cancer patients who receive radiotherapy in and around the acoustic structures are at extremely high risk of suffering hearing loss. Yet, radiotherapy-induced ear injuries remain under-evaluated and under-reported.
Up to 40 percent of patients suffer acute middle ear side effects from radical irradiation with acoustic structure involvement, and about one third of patients develop late sensorineural hearing loss (SNHL), according to a report written by researchers at Ist Europeo Oncology, Department of Radiation Oncology in Milan, Italy. These reactions may have acute or late character, may affect all structures of the hearing organ, and may result in conductive, sensorineural, or mixed hearing loss.
"Total radiotherapy dose and tumour site seem to be among the most important factors associated with the risk of hearing impairment," wrote B.A. Jereczek-Fossa and colleagues in the report. "Thus, reduction in radiation dose to the auditary structures should be attempted whenever possible."
The Italian researchers point out that new radiotherapy techniques (3-dimensional conformal irradiation, intensity-modulated radiotherapy, proton therapy) allow better dose distribution with lower dose to non-target organs.
The treatment of acute and late external otitis includes topically and systematically applied anti-inflammatory agents, according to the researchers. Post-radiation chronic otitis media and the Eustachian tube pathology may be managed with tympanic membrane incision with insertion of a tympanostomy (grommet), although the benefit of this approach is controversial and some authors advocate a more conservative approach.
To alleviate the functional deficit, bone conduction hearing aids may be applied. Corticosteroid therapy, rheologic medications, hyperbaric oxygen or carbogen therapy are usually employed for post-irradiation sudden or progressive SNHL, although the authors note that no standard therapy exists, and that the published data on the various treatment modalities are controversial. In some cases with profound bilateral hearing loss or deafness, cochlear implants may prove effective. But the researchers add, that better prevention and management of radiation-related acoustic injury depends on further improvements in radiotherapy techniques and progress in otologic diagnostics and therapy.
Sources: Cancer Treatment Reviews, 2003; 29(5): 417-430, Jereczek-Fosse and colleagues: Radiotherapy-induced Ear Toxicity. Biotech Week, November 26, 2003.
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