Local Heat-Stress as a Mechanism of Hearing Preservation in Adults Treated With Cisplatin: A Pilot Study

Evidence from the laboratory over the past 10-15 years has demonstrated that heat stress to the ear is otoprotectant against a variety of insults. The strongest evidence supports heat-shock protein 70 (Hsp70) as a key facilitator in this protection. Hsp70 is well established as a cell stabilizer, especially for cells undergoing significant stress. Hsp70 has been shown to protect against cisplatin-induced ototoxicity. Induction of Hsp70 may be accomplished pharmacologically, by whole-body heat stress, or by local heat stress. A form of local heat-stress is already employed in the common clinical setting of the warm caloric. This vestibular test has been in place since the early 20th century with a variety of studies evaluating the patient vestibular response to a variety of times and temperatures. Current clinical practice recommends either water or air calorics of 45°C or 50°C (respectively) at 45-60 seconds.

Several studies have described administering prolonged caloric stimulation to individual subjects without ill effect. Patients are able to tolerate stimulation up to 60 minutes without intolerable nystagmus or vertiginous symptoms or significant injury. Thus, it is feasible to provide warm stimulus to the ear for the recommended time of 30 minutes at the recommended temperature of 50°C (air) without significant risk to the patient.

The purpose of this study is to evaluate the impact of heat stress to the inner ear as an otoprotectant intervention against cisplatin-induced hearing loss. Patients that meet inclusion criteria will be offered audiometric evaluation before each cisplatin treatment and at 1, 3, 6, and 12 months following their chemotherapy. Patients will undergo their heat-stress 5-7 hours prior to their cisplatin treatment. Patients will serve as their own controls with one ear randomly receiving treatment and the other not. The primary outcome will be audiometric testing. Blood samples will be collected for serum levels of Hsp70 as a secondary outcome. A sample size of 12 achieves 80% power to detect a 0.9 standard deviation difference between ears using a two-sided paired t-test at 0.05 significance level.