1) Protocol version 3.0 dated 03 May 2021: We decided to modify our exclusion criteria as they excluded to many patients and were not consistent with our clinical practice. Indeed, N-acetylcystein (NAC) has demonstrated protective effects against cisplatin induced ototoxicity in previous clinical trials (ref 14,15 of the protocol). In these trials, only one ear was injected with N-acetylcystein while the other was control or receiving another drug. In these studies, authors excluded patients with middle ear disease or eardrum perforation. We have begun our trial with 2 of our exclusion criteria: - Pathological findings on otoscopy that do not allow safe intratympanic drug delivery and reliable distortion product otoacoustic emissions (DPOAEs) testing. - Conductive hearing loss > 10dBHL. The problem of those criteria is that we had to exclude patients with serous media otitis. However, patients with rhinopharynx carcinoma often suffer from this condition and need transtympanic drainage to restore their hearing. The primary objective of our trial is to evaluate the protecting effect of NAC 10% against Cisplatin-induced ototoxicity. In this case, we will evaluate its effect through the transtympanic administration in both ears. If the treatment is contributive, we aim to implement it as the future gold standard to prevent cisplatin induced ototoxicity. In order to do it, we need to show that the treatment is effective in clinical practice. In clinical practice, the first line of treatment of patient with rhinopharynx treatment is radiotherapy and radiochemotherapy with cisplatin. Therefore, we deleted the exclusion by the impossibility to allow reliable DPOAEs testing as with a transtympanic drainage, DPOAEs will often be impossible to test. We decided to extend to conductive hearing loss up to 20 dBHL as patients with tympanic drainage will often have a small conductive hearing loss less than 20 dBHL. 2) The reference safety information was updated for NAC.