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Radiation Oncology/Toxicity/Inner Ear

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Inner Ear RT Tolerance


  • Gardner Robertson scale is used for hearing evaluation. Non-serviceable hearing is typically >50 dB audiogram and <50% speech discrimination
  • Sensorineural hearing loss begins to occur around 45 Gy, and is significantly increased at ~60 Gy
  • Patients treated with curative doses for H&N can experience damage to all parts of the auditory system, at rate ~30%
  • For single fraction, cochlea/modiolus dose should be kept <5.3 Gy and possibly <4.2 Gy (else increased chance of high frequency hearing loss), ventral cochlear nucleus <= 9 Gy (else increased chance of low frequency loss)


Gardner Robertson Scale

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  • Grade I (good-excellent)
    • pure tone audiogram (dB) : 0-30
    • speech discrimination (%) : 70-100
  • Grade II (serviceable)
    • pure tone audiogram (dB) : 31-50
    • speech discrimination (%) : 50-69
  • Grade III (non-serviceable)
    • pure tone audiogram (dB) : 51-90
    • speech discrimination (%) : 5-49
  • Grade IV (poor)
    • pure tone audiogram (dB) : 91-max
    • speech discrimination (%) : 1-4
  • Grade V (none)
    • pure tone audiogram (dB) : not testable
    • speech discrimination (%) : 0
  • If PTA and speech do not correlate, use lower class.

Adults

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Fractionated

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  • Utah; 2009 PMID 18707819 -- "Relative contributions of radiation and cisplatin-based chemotherapy to sensorineural hearing loss in head-and-neck cancer patients." (Hitchcock YJ, Int J Radiat Oncol Biol Phys. 2009 Mar 1;73(3):779-88. Epub 2008 Aug 15.)
    • Retrospective. 62 H&N patients. RT alone 34%, concurrent cisplatin 40 mg/m2 QW 44%, concurrent cisplatin 100 mg/m2 Q3W 21%, concurrent Erbitux 1%
    • Outcome: RT only: No significant hearing loss <40 Gy. If cisplatin, high frequency SNLH at 10 Gy, significant hearing loss by 40 Gy
    • Conclusion: High-frequency SNHL profoundly damaged in patients with concomitant cisplatin
  • University of Florida; 2007 (1964-2000) PMID 17236969 -- "Ototoxicity after radiotherapy for head and neck tumors." (Bhandare N, Int J Radiat Oncol Biol Phys. 2007 Feb 1;67(2):469-79.)
    • Retrospective. 325 patients treated for H&N tumors. Median F/U 5.4 years
    • Toxicity: overall 42%; external ear 33%, middle ear 29%, inner ear 27%. Sensorineural hearing loss (SNHL) in 15%
    • Predictors for SNHL: age, cochlear dose, chemo-RT. 10-year risk dose <60 Gy 3% vs. >60 Gy 37% (SS). Chemo-RT 30% vs. RT alone 18% (SS). Threshold for SNHL not determined
    • Conclusion: RT toxicity in all parts of auditory system. Median dose for incidence 60-66 Gy
    • Comment (PMID 17674992): 60 Gy probably too high, as prospective studies suggest 32-50 Gy
  • Michigan; 2005 - PMID 15817342 — "Prospective study of inner ear radiation dose and hearing loss in head-and-neck cancer patients." (Pan CC et al. Int J Radiat Oncol Biol Phys. 2005 Apr 1;61(5):1393-402.)
    • Prospective. 35 patients, curative RT for H&N cancers. Baseline auditometry, then 1, 6, 12, 24, and 36 months after RT. Median dose ipsilateral ear 47.4 Gy (14.1-68.8), contralateral ear 4.2 Gy (0.5-31.3 Gy). Follow up 2 years
    • Outcome: Dose >=45 Gy had hearing loss of ~210 dB, mostly in higher frequencies. Model predicts ~19 dB hearing loss at 45 Gy, but depends on age and other factors.
    • Conclusion: High-frequency (>= 2000 Hz) worsens significantly after RT in dose-dependent fashion

Single fraction

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  • Pittsburgh; 2009 (2004-2007) PMID 19284227 -- "Predictors of hearing preservation after stereotactic radiosurgery for acoustic neuroma." (Kano H, J Neurosurg. 2009 Mar 13. [Epub ahead of print])
    • Retrospective. 77 patients, serviceable hearing (Gardner-Robertson Class I-II), treated with SRS. Margin dose 12-13 Gy. Median F/U 20 months
    • Outcome: Serviceable hearing preserved in 71% of all patients, in 89% of GR Class I patients
    • Prognostice factors for maintaining hearing: GR Class I, speech discrimination score >= 80%, pure tone average <20 dB, age <60. Significantly better hearing preservation of GR Class if central cochlea dose <4.2 Gy
    • Conclusion: GKS preserves serviceable hearing in majority of patients; a low dose to cochlea enhances hearing preservation
  • UC Irvine; 2008 PMID 19123899 -- "Hearing preservation in vestibular schwannoma stereotactic radiosurgery: what really matters?" (Linskey ME, J Neurosurg. 2008 Dec;109 Suppl:129-36.)
    • Review. Tumor margin delineation to exclude cochlear nerve, dura mater of anterior border of internal auditory canal
    • Tumor dose <= 12 Gy
    • Ventral cochlear nucleus <= 9 Gy; toxicity can lead to loss of low hearing frequencies
    • Modiolus and basal turn of cochlea <5.3 Gy, toxicity can lead to loss of high hearing frequencies
    • Serous otitis media, ossicular or temporal bone osteonecrosis, and chondromalacia not likely to be relevant


Pediatric

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  • St. Jude; 2008 (1997-2001) PMID 18395355 -- "Hearing Loss After Radiotherapy for Pediatric Brain Tumors: Effect of Cochlear Dose." (Hua C, Int J Radiat Oncol Biol Phys. 2008 Apr 3. [Epub ahead of print])
    • Prospective. 78 patients (155 ears) with brain tumors. No platinum-based chemo. Prospective audiograms and/or auditory brainstem response at baseline, and then q6 months
    • Outcome: Hearing loss 14% patients, 11% cochlea. Onset at 3-5 years after RT. Incidence low at 30 Gy, increased at 40-45 Gy. risk greater at high frequencies (6-8 kHz)
    • Conclusion: SNHL is a late effect of conformal RT, and shows dose-response. Cumulative cochlear dose <35 Gy is recommended
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