Of the 20 cases reviewed by the RCP, 15 were judged “unsatisfactory overall”, meaning care was found to be well below expected standards.
Four were rated as requiring improvements in both clinical and organisational care, while one needed improvement in clinical care alone.
No cases were judged to represent good practice.
There was “scant evidence” of the understanding and documentation of the risks of taking the drug, the review team found.
Guidelines say TMZ should usually be taken post radiotherapy for six cycles, usually over six months.
But many patients have told the BBC they received it for many years – in one case 16 – and believe they suffered physical and emotional harm as a result.
There are a wide range of side effects associated with the drug, including muscle weakness, memory issues and, in rare cases, secondary cancers and liver damage.
According to the report, in one case, a patient received more than 100 cycles of TMZ before doctors identified that they had a different, less aggressive type of tumour than originally believed.
The patient later developed acute myeloid leukaemia, a serious blood cancer, after showing signs of bone marrow suppression.
The report said there was “insufficient clinical curiosity” in some cases and a lack of collaboration with multidisciplinary team colleagues, allowing potential diagnostic errors to persist.
The report was “damning” and showed “all levels of oversight failing” at the trust, said Becky Addison of law firm Brabners.
The interim report was sent to the chief medical officer of the NHS trust in April, and has only now been seen by patients, their legal representatives and the BBC.
It was “extremely disappointing” added solicitor apprentice Addison.
“Patients have had so much of their lives taken away from and they deserve answers, and there’s still so many more answers that they are yet to be given,” she added.
“Personally, I would like the two people at the centre of this report criminally prosecuted,” added Bown.
