BBC News website age & disability correspondent
Drugs companies are being urged to do more to combat hearing loss among cancer patients having chemotherapy.
Platinum-based drugs can damage a patient's hearing
The Royal National Institute for Deaf people (RNID) says thousands are suffering "unnecessary" hearing damage caused by anti-tumour agent cisplatin.
It is urging the pharmaceutical industry to develop drugs that block chemotherapy's damaging side-effects.
Such drugs have already been identified but the RNID claims that more should be spent on research and development.
Inner ear damaged
The charity has the backing of Penelope Brock, a leading British oncologist based at London's Great Ormond Street Hospital, who says robust trials of the new drugs should be carried out as soon as possible.
The hearing damage is caused by cisplatin - a platinum-based chemotherapy which is one of the most effective anti-tumour agents.
But it also causes damage to the inner ear which can lead to hearing loss, balance problems and tinnitus - a buzzing or ringing in the ears.
Cisplatin is used to treat almost 70,000 cancer patients a year in the UK.
It has been available since the 1970s, and is used to treat 30% of cancers in children and about 25% of adult cancers.
"Thousands of survivors are being left with unnecessary hearing damage," said RNID commercial research manager, Munna Vio.
"Our research indicates that if a suitable drug was approved that effectively protected against hearing loss, but did not interfere with chemotherapy, oncologists would use it across the board for all cancers treated with cisplatin."
Ms Vio says the industry should seize the opportunity to deliver drugs to protect patients' hearing.
Anthony Khodayeki has survived cancer but has damaged hearing
Dr Brock says that the cure rate for childhood cancer has improved considerably and now exceeds 70%, and that cisplatin has played a large part in this.
"However, this cure is not without cost to the child," she said.
"Permanent side-effects are the most damaging, and hearing loss is one which affects everyday life and development," she said.
Dr Brock says that preventing hearing loss in children would transform their lives and futures.
The drugs that would help combat the hearing damage caused by cisplatin are known as otoprotectants.
Thorough clinical trials to determine the drug's effectiveness, correct dosage and the timing in the chemotherapy cycle are the vital next step, according to Dr Brock.
Without this, the otoprotectant might reduce hearing damage but lessen the effect of chemotherapy on a tumour.
Dr Brock thinks that with substantial investment in research and development, a proven otoprotectant could be used in hospitals within one to two years.
The RNID is sitting around the table with representatives of the pharmaceutical industry this week to persuade them of the business case for developing otoprotectants.
Its research suggests that there would be a £500m market for a successful otoprotectant.
When Anthony Khodayeki was just four days old, he was diagnosed with liver cancer.
He has been cured using platinum-based drugs and surgery, but he has substantial hearing loss.
Now aged five, Anthony has been fitted with hearing aids and has shown significant progress from the quiet, withdrawn toddler he once was.
"The last few years have been very difficult for us," said Anthony's father John Khodayeki.
"We are so relieved that Anthony has survived, but we would urge drug companies to develop something to protect hearing during treatment."
Some of the research conducted among very young cancer patients showed that after a certain level of hearing loss, children gave up speaking altogether.
The RNID hopes that the industry will respond to what it sees as a pressing clinical need.