An trust is probing whether its poor record keeping was responsible for 25 patient deaths.
Imperial College Healthcare came under fire after it failed to properly maintain files on more than 1,000 patients who were referred to them for treatment.
Files on some patients were opened but not closed, while others were duplicated.
The blunder has seen the trust, which runs five hospitals in London, have to contact GPs about 1,023 patient files to check whether their records are correct.
When the trust contacted GPs, it was discovered that 74 cancer patients had died.
It commissioned a clinical review group to assess whether the deaths were associated with the data error.
While 49 of the deaths have been ruled out, 25 are still under scrutiny to see whether the deaths could have been prevented had the records been properly kept.
But the trust - which runs Charing Cross Hospital, Hammersmith Hospital, Queen Charlotte’s and Chelsea Hospital, St Mary’s Hospital and the Western Eye Hospital - said it did not believe any patient had come to serious harm.
It said that of the 1,023 patients, 15 patients who were suspected to have cancer were invited back for further testing.
Ten of them were found to be cancer-free and five additional patients have been invited back to be tested “as a matter of urgency”, a trust spokeswoman said.
She said: “Our patients’ safety has been our absolute priority while we have addressed issues in the way we record our data.
“We have carried out a thorough clinical review of records of patients that were referred to us for suspected cancer where we had not recorded that the patients had been seen and, where appropriate, treated.
“To date, we have found no evidence that these patients have come to clinical harm as a result of our poor record keeping.
“Fifteen patients have been re-referred and to date none have been found to have cancer.
“Seventy-four patients have been found to have died before we had checked their records and again, to date, an independent clinical review group has found that there is no correlation between the reason for death and this data reporting issue.
“We are extremely sorry that this situation was not identified and resolved earlier however, we would like to reassure our patients that this was an issue of poor record keeping not clinical care.”