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CAR-T immunotherapy remains a viable option for patients who have lymphoma -- a group of blood and lymph tumours -- that goes into remission before the cell therapy begins, according to a study.

Most patients receiving cell therapy, a form of immunotherapy that uses immune cells engineered to recognise and attack the patient’s cancer, desperately need it. For some, it comes after many other treatments have failed.

But researchers noticed an odd phenomenon in the past few years when treating lymphoma patients with this form of therapy: Some of the patients went into complete remission before the cells ever touched their bodies.

This uncommon scenario occurs during the process of getting to cell therapy, which in the case of the study uses a kind of engineered immune cell known as CAR-T cells.

While the study doesn’t answer the question of whether cell therapy in remission is the right choice, it does say that it’s not the wrong choice.

“I don’t think it answers the question of: Should we give these patients cell therapy? But I think it answers the question that we can -- that it’s safe and that it’s a reasonable strategy when you’re in that spot,” said Trent Wang, a haematologist and cellular therapy specialist at Sylvester Comprehensive Cancer Centre at the University of Miami Miller School of Medicine.

The study findings will be presented in an oral presentation at the 65th ASH Annual Meeting and Exposition, the American Society of Hematology’s conference taking place in San Diego, California.

When a patient starts the process, there’s a waiting period of three to five weeks before they get the treatment. Insurance approval is needed, and the cells themselves need to be manufactured from the patient’s own cells. But many of these patients are very sick with their cancer, so physicians will often treat them with a short course of chemotherapy or other drugs to tamp down the symptoms.

A small handful of these patients end up in remission during this waiting period treatment, the clinicians have found.

Wang and his colleagues noticed that their patients who received the cells while in remission tended to fare well after their infusion. But they didn’t know if those results would hold up in an analysis of a larger group.

To explore, they proposed a research study on 134 patients from a nationwide registry who had gone into complete remission in the waiting period before receiving their cell therapy. To find that group, the scientists screened the records for more than 5,000 cell therapy patients.

They found that this group of patients had a 43 per cent probability of progression-free survival over the two years following their treatment, about the same percentage as patients in the registry who were not in remission when they received CAR-T.

However, the patients in remission had very low levels of toxicities related to their cell therapies, namely an immune overreaction known as cytokine release syndrome and neurotoxicity, two side effects that can sometimes accompany CAR-T cell therapy.