A cancer patient has spent more than 14 years receiving unnecessary chemotherapy, hospital bosses have admitted.

Lawyers representing the man claim they know of 12 more patients – all in Coventry – saying his case is the “tip of the iceberg”.

NHS Guidelines recommend the chemotherapy drug he was originally prescribed, temozolomide, should not be used for more than six months.

University Hospitals Coventry and Warwickshire NHS Trust (UHCW) said it was carrying out an internal review into what happened, and stressed it was committed to providing the best care for its patients.

Lawyers for the patient claim that long-term treatment with temozolomide risks secondary cancer, chronic liver problems and reinforces the fear of death.

The patient, who was originally treated for a cancerous brain tumour, said he had suffered fatigue, joint pain, gastrointestinal distress, recurrent mouth ulcers and nausea, because of the ongoing treatment.

His prolonged chemotherapy programme was only discovered when the consultant treating him, Prof Ian Brown, retired.

A consultant who took over his care then confirmed the four-week cycles of chemotherapy he was undertaking were not needed.

A letter from the trust’s chief executive, Ian Hardy, to the patient’s mother admitted the treatment her son had received “was not evidence-based”.

“I cannot imagine the impact that this has had on him. I wish to apologise on behalf of the trust for your son going through unnecessary treatment,” Mr Hardy wrote.

Prof Brown has since been referred to the General Medical Council by Brabners, the law firm representing the patient.

The GMC has also placed Prof Brown under interim restrictions, with conditions on his ability to practise. He cannot prescribe, administer, or have primary responsibility for any chemotherapy drugs pending a full investigation.

Fiona Tinsley, head of clinical negligence and serious injury at Brabners, said: “Enduring repeated waves of temozolomide chemotherapy for more than a decade has taken a significant toll on our client’s health, wellbeing, and quality of life.

“It has restricted their options in terms of their education and career and made starting a family incredibly stressful.”

Paralegal Becky Addison said the firm was aware of at least a dozen other affected patients.

“[They] have been through similar unnecessary long-term courses of this temozolomide chemotherapy, but this is likely to be the tip of the iceberg with many more lives impacted,” she said.

UHCW accepted that the National Institute for Health and Care Excellence (NICE) only recommends usage for six months and that the patient had received the drug for more than 15 years.

The trust has declined to answer any further questions, which it said would be dealt with as part of the internal review.

Chief executive officer at UHCW, Prof Andy Hardy, said: “We take very seriously any allegation that care provided by a member of staff, past or present, may have fallen below the standards we would expect for our patients.

“I can confirm we are undertaking an internal review of this matter and, once that has been completed, we will consider what further steps may be necessary.”

Temozolomide is used to treat an aggressive form of brain tumour called a glioblastoma.

Only 2% of patients with this type of tumour survive longer than 10 years.