Chronic Lymphocytic Leukemia

Peripheral blood film from a 70-year-old woman with an absolute lymphocyte count of 41,000/uL / Ed Uthman

Engineering immune cells to hunt and destroy cancer cells might be able to help acute lymphoblastic leukaemia (ALL) patients live much longer than standard therapies, according to new research. The work was presented at the American Association for Cancer Research’s annual meeting on Monday by Jae Park, M.D., from the Memorial Sloan Kettering Cancer Centre in New York.

In the USA, 5,970 people are predicted to develop ALL in 2017 alone, and there are an expected 1,440 deaths as a result of the condition. ALL affects B cells, a component of the immune system produced in the bone marrow, causing them to grow out of control and spread to other tissues in the body. The condition has a five year survival rate of 71%, but less than 10% of patients survive for five years after a relapse.

To try to combat this, Park and his team used genetic engineering to modify T cells from 51 patients who had either failed to respond to initial treatment or who had relapsed. The CAR-T cells they produced (Chimeric Antigen Receptor T-cells) were able to target a patient’s rogue B cells and destroy them.

Of the 51 patients, 20 displayed leukaemia cells that took up less than 5% of their overall bone marrow. Upon treatment, 95% of this subset showed a complete response to the treatment and no longer have any signs of leukaemia. One patient in particular remains healthy five years after treatment was completed.

The remaining 31 patients however, who had more than 5% of their bone marrow taken up by leukaemia cells, displayed less positive results. The initial responses were promising, but after a median of 6.3 months, the cancer came back and the patients relapsed. The median survival rate for this subgroup was 17 months, although some patients are still alive after 3 years.

The second group also suffered from more pronounced side effects than the first, including cytokine release syndrome, a type of immune reaction, and nerve problems.

Park has said that his team are still uncertain about why the two groups demonstrated such different responses to the treatment but they hope to investigate further. He also pointed out that while there were some downsides to their technique, it still displays a better survival rate than more traditional treatment plans.

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