A patient developed a rare and fatal form of blood cancer just one month after receiving chimeric antigen receptor (CAR) T-cell therapy, according to a recent case study published in the New England Journal of Medicine. The authors wrote that CAR T-cell therapy, which treats cancer by modifying the genes of a patient’s immune cells, did not cause the T-cell lymphoma. CAR T-cell therapy has improved the prognosis for several blood-related cancers by utilizing patients’ own immune cells to fight cancer more effectively.

However, as the treatment becomes more widespread, concerns are growing over rare but serious adverse effects, including the development of secondary cancers. The patient had clonal hematopoiesis, a condition where some blood stem cells acquire changes to their DNA and multiply more than usual. The condition tends to occur alongside aging and, though it is not cancerous, can increase cancer risk.

These abnormal cells were present before the patient received treatment, which led some of his cancer-fighting CAR T-cells to contain such mutations. Kobbe said that cells used in CAR T-cell production are now being more frequently screened for clonal hematopoiesis. “This was one of our patients whom we had been treating for many years.

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We were pleased to have successfully treated him with CAR T-cells,” Kobbe shared in an email. Kobbe’s team was surprised when, two months after the CAR T-cell infusion, the patient’s condition suddenly worsened, and he di.