Too early to hail success of T-cell cancer therapy

Proclamations of “extraordinary” success by doctors or scientists should always set alarm bells ringing. And so claims yesterday of such success in efforts to engineer immune cells to target a specific type of blood cancer are, on the face of it, premature.

A small study presented to the annual meeting of the American Association for the Advancement of Science (AAAS) found that use of the patient’s own immune system T-cells resulted in over 90 per cent of participants, who had acute lymphoblastic leukaemia, becoming symptom free.

To administer the T-cell therapy, doctors remove immune cells from patients, tagging them with “receptor” molecules that target a specific cancer, as other T-cells target the flu or infections. They then infuse the cells back in the body.

Immune system

T-cells are an important component of the immune system’s response; they are especially helpful because of their ability to not only kill the target but also to persist in the body as a memory cell ready to challenge recurrence of illness.

Acknowledging the unexpected results in patients with advanced cancer, lead researcher Prof Stanley Riddell of the Fred Hutchinson Cancer Research Centre in Seattle, Washington, said: “This is unprecedented in medicine, to be honest, to get response rates in this range in these very advanced patients.” The 35 patients were estimated to have no more than five months to live.

In a separate Italian study, some 10 patients who had received a bone marrow transplant for leukaemia were given a T-cell infusion. The engineered T-cells were still present 14 years later.

Prof Chiara Bonini, a haematologist at San Raffaele University in Milan who carried out the trial, said she had not seen remission rates like this in over 15 years of work. She hopes the modified memory T-cells could eventually provide a long-term defence against cancer, using cells that “remember it from 10 years earlier, and kill it so quickly you don’t even know you’re infected”.

So why the note of caution? The number of participants in the trials are extremely small. The research was not blinded, nor was there a comparison with other standard treatments. There was no estimate of how long patients would remain in remission using the novel T-cell therapy. And we need to see how the therapy works in other cancer forms.

Side-effects were not insignificant: some patients experienced fever, low blood pressure and neurotoxicity due to cytokine release syndrome , with two deaths as a result. These need to be studied in more detail and, like the treatment, tested in thousands of patients before it could be placed in front of drug regulators for approval.

While immunotherapy looks promising it would be premature to expect it to replace chemotherapy or radiotherapy any time soon. (Additional reporting, Guardian Service)