Transtympanic Sodium Thiosulfate for Prevention of Cisplatin-Induced Ototoxicity: A Randomized Clinical Trial

To determine safety, feasibility, and preliminary activity of transtympanic injection of sodium thiosulfate (STS) against cisplatin-induced hearing loss (CIHL).DESIGN Randomized controlled trial.SETTING Tertiary cancer hospital.PATIENTS Adults to be treated with high-dose cisplatin (≥ 75 mg/m2).INTERVENTION Selected by randomization, 0.1 M STS gel on one side and placebo gel on the other side was transtympanically applied to the middle ear 3 hours before cisplatin administration. After amendment, the placebo ear was left untreated.

Primary outcome was safety and feasibility. Secondary outcomes included pharmacokinetic analysis of systemic cisplatin and preliminary activity of STS. Clinically relevant CIHL was defined as a ≥ 10 dB threshold shift at pure-tone average 8-10-12.5 kHz (PTA8-12.5). Response to STS was defined as a threshold shift at PTA8-12.5 in the STS-treated ear of ≥ 10 dB smaller than the untreated ear.

Twelve patients were treated. Average CIHL at PTA8-12.5 was 12.7 dB in untreated ears and 8.8 dB SPL in STS-treated ears (p = 0.403). Four patients did not develop CIHL. Four out of eight patients with CIHL responded to STS: CIHL at PTA8-12.5 in STS-treated ears was 18.4 dB less compared to untreated ears (p = 0.068). Grade 1 adverse events were reported. Pharmacokinetic results were available for 11 patients.

Transtympanic application of STS was safe and feasible. Based on our pharmacokinetic analysis, we postulate that transtympanic STS does not interfere with the systemically available cisplatin. Our results provide a preliminary proof of concept for transtympanic application of STS in preventing CIHL and warrants further evaluation on a larger scale.