We reach out to physicians by sending monthly fax and email educational pieces. Our Audiologist Diana Holan, MS, wrote this section for a recent physician outreach. I wanted to pass it along in today’s post.
Incidence of hearing loss as a side effect of chemotherapy (i.e. cisplatin and carboplatin) is well documented, although it usually is reported only for patients in Grade 3 (needs intervention) and 4 (needs CI) levels. Clinical trials to reduce ototoxicity have only included these patients.
By contrast, patients with hearing loss at Grade 1 and 2 levels, which includes high frequency hearing loss, is underreported, even though it is common and has far reaching effects. So, it is critical for all who receive chemotherapy to have initial and ongoing audiologic evaluations.
Especially in children, hearing loss can be difficult to recognize without adequate testing. High frequency and minimal hearing loss results in developmental delays, (i.e. language, education and family/social relationships). Results of a study in 1998 of 1200 children with minimal hearing loss showed “37% failed at least one (school) grade, compared with the normal rate of 3%.” An OHSU study found hearing loss ranging from 55%-84% of young patients treated with the platin drugs, and that 36% of the audiograms fell within Grades 1-2.
This issue has become more important because new research looks at adding drugs and other considerations to the platin treatments to reduce the associated hearing loss. One experiment showed that treating patients with sodium thiosulfate (STS) four hours after receiving the carboplatin, “ (decreased) …ototoxicity from 84% (to) 29%.” A second “chemo-protectant” under study is N-acetylcysteine (NAC), which may be used with STS to further reduce ototoxicity. In addition, Canadian geneticists, evaluated two groups of children in Canada (54 and 112 patients), and found “…variants in two genes – (TPMT and COMT) – were significantly linked with cisplatin-induced hearing loss.” Further research studies should include all hearing loss levels, so that all patients have the potential for an improved quality of life.
Diana has been practicing audiology for over 20 years in Tucson and is committed to improving communication between patients and their families through the use of state-of-the-art hearing aid technology and various assistive techniques. She received a Bachelor’s of Science in Speech and Hearing and a Master’s of Science in Audiology from the University of Arizona.
Toxicity profile of delayed high dose sodium thiosulfate in children treated with carboplatin in conjunction with blood-brain-barrier disruption. Neuwelt EA, et al, Pediatr Blood Cancer 2006 Aug: 47(2): 174-82.
Delayed sodium thiosulfate as an otoprotectant against carboplatin-induced hearing loss in patients with malignant brain tumors. Doolittle ND, et al, Clin Can Research 2001 Mar;7 (3); 493-500.
TPMT and COMT genetic variants are predictive for severe hearing loss in children receiving cisplatin chemotherapy. Ros CJD, et al Nat Genet 2009.