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Single Fraction & Hypofractionated Radiation Cause Cochlear Damage, Hearing Loss

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donjehle:
https://pubmed.ncbi.nlm.nih.gov/37345155/

skier:
 Single Fraction and Hypofractionated Radiation Cause Cochlear Damage, Hearing Loss, and Reduced Viability of Merlin-Deficient Schwann Cells
Christine T Dinh  1   et al

    PMID: 37345155 PMCID: PMC10216287 DOI: 10.3390/cancers15102818

Abstract

Background: Vestibular schwannomas (VS) are benign intracranial tumors caused by loss of function of the merlin tumor suppressor. We tested three hypotheses related to radiation, hearing loss (HL), and VS cell survival: (1) radiation causes HL by injuring auditory hair cells (AHC), (2) fractionation reduces radiation-induced HL, and (3) single fraction and equivalent appropriately dosed multi-fractions are equally effective at controlling VS growth. We investigated the effects of single fraction and hypofractionated radiation on hearing thresholds in rats, cell death pathways in rat cochleae, and viability of human merlin-deficient Schwann cells (MD-SC).

Methods: Adult rats received cochlear irradiation with single fraction (0 to 18 Gray [Gy]) or hypofractionated radiation. Auditory brainstem response (ABR) testing was performed for 24 weeks. AHC viabilities were determined using immunohistochemistry. Neonatal rat cochleae were harvested after irradiation, and gene- and cell-based assays were conducted. MD-SCs were irradiated, and viability assays and immunofluorescence for DNA damage and cell cycle markers were performed.

Results: Radiation caused dose-dependent and progressive HL in rats and AHC losses by promoting expression of apoptosis-associated genes and proteins. When compared to 12 Gy single fraction, hypofractionation caused smaller ABR threshold and pure tone average shifts and was more effective at reducing MD-SC viability.

Conclusions: Investigations into the mechanisms of radiation ototoxicity and VS radiobiology will help determine optimal radiation regimens and identify potential therapies to mitigate radiation-induced HL and improve VS tumor control.

skier:
In above comment, I simply cut and pasted the summary of the study as published at the link in Don's post.

I edited ONLY the author names, signifying that by adding "et al", meaning "and others".

Here are a few of my comments, as a lay reader:

1- This study was on rats.
2- Hypo-fractionated radiation may have benefits compared to single dose radiation re: hearing loss.
3- Hypo-fractionated radiation may have benefits compare to single dose radiation re: control of Schwann cell growth.

And, importantly, the conclusion states that studies like this one "will help determine optimal radiation regimens and identify potential therapies to mitigate radiation-induced HL [hearing loss] and improve VS [vestibular schwannoma" tumor control."

I think, as a patient, that medical consensus about the best treatment choice is something I hope for.

Good to learn of this study, and hope that AN-treating medical doctors will find it informative.

Thanks for the link, Don.

donjehle:
Thank you, skier, for listing the abstract and for your great comments!

mwatto:
I had three CK radiotherapy and tbh I am not aware of any hearing loss- 5 years out. I have audiograms every year and still around 85- 90% in that ear. Am 63 years old in Jan. Update- audiology test this year shows no hearing loss difference from previous years. Am 85% in AN ear still (same at diagnosis).

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