New findings on cell therapy to treat leukemia bring more encouraging news of the promise that this experimental area of cancer treatment holds for patients for whom conventional approaches do not work.
In the journal Science Translational Medicine, researchers from Memorial Sloan Kettering Cancer Center, New York, NY, report the results of the largest clinical study yet conducted in patients with advanced leukemia.
These show that 14 of the 16 patients - that is 88% - treated with genetically modified versions of their own immune cells, achieved complete remission - at least in the short term; the long-term effects of the therapy are yet to be tested.
Co-senior author Dr. Michel Sadelain, director of the Center for Cell Engineering at Memorial Sloan Kettering, describes the results as "extraordinary," saying they show how cell therapy might offer hope where other treatments have failed.
"Our initial findings have held up in a larger cohort of patients," he notes, "and we are already looking at new clinical studies to advance this novel therapeutic approach in fighting cancer."
Cell therapy programs patients' immune cells to target cancer cells
The researchers tested the cell therapy approach in patients with a type of blood cancer called adult B cell acute lymphoblastic leukemia (B-ALL). According to the American Cancer Society, about 6,000 Americans will be diagnosed with ALL in 2014.
B-ALL is difficult to treat because most patients relapse after receiving conventional chemotherapy. Only 30% survive further chemotherapy, and without a bone marrow transplant, long-term prospects are very grim.
The cell therapy approach the researchers used, also called cancer immunotherapy, involves extracting immune T cells from the patient, genetically altering them to recognize and destroy cancer cells that contain the protein CD19, and then infusing them back into the patient.
In 2013, the team reported how their leukemia cell therapy led to complete remission in five of the 16 patients treated.
This latest study includes results for the other 11 patients and reports that overall, of the 16 patients, 88% showed a "complete response," which means there was no molecular evidence of the disease.
Long-term effects of cell therapy for leukemia yet to be tested
However, the long-term effect of the therapy is yet to be thoroughly tested, as some of the patients in the study became eligible for bone marrow transplants following treatment, offering a chance for prolonged survival. Bone marrow transplant is the standard of care and the only curative option for B-ALL patients.
The Wall Street Journal reports Dr. Sadelain as saying, "At that point, we weren't running an experiment, we were trying to keep people alive."
Seven of the 16 patients underwent bone marrow transplant - two of whom died of complications. Another patient is currently being evaluated for transplant.
The researchers point out that historically, only 5% of patients with relapsed B-ALL have been able to move forward to bone marrow transplantation.
Of the remaining eight patients, four died, and four remain in remission, including one who is still in remission more than 2 years after receiving cell therapy.
Study offers guidelines for managing side effects of cell therapy
The study also offers valuable guidelines for how to manage cell therapy side effects, which can include flu-like symptoms such as fever, low blood pressure, muscle pain and difficulty breathing, a condition known as cytokine release syndrome. The team developed a test that can identify which patients are at greater risk for this syndrome.
More research looking at applying cell therapy to other cancers is already under way, as are plans to study whether it might benefit B-ALL patients as a frontline treatment.
Funds from various research foundations and institutes, including the National Cancer Institute and the Terry Fox Foundation, helped finance the study.
Written by Catharine Paddock PhD