Editor's note: This story was first published in Dec. 2016, when the results of this study were presented at the American Society of Hematology's annual meeting. It has been updated to reflect the researchers' publication on Monday of their results in the Journal of Clinical Oncology.
The published paper shows that about 70 percent of patients with the most common adult leukemia had their tumors shrink or disappear following an experimental immunotherapy based on chimeric antigen receptor (CAR) T cells. The researchers also found that measuring genetic traces of cancer cells taken from bone marrow biopsies might be a better indicator of prognosis than the standard lymph node scan.
The 24 patients had undergone most standard therapies available to them and yet their chronic lymphocytic leukemia had come back strong. Almost all of them had been treated with a newly approved, targeted drug called ibrutinib; data from other studies show that most patients whose disease progresses after ibrutinib treatment do not survive long. The majority of the 24 had chromosomal markers in their leukemia cells serve as “predictors of a bad response to most standard therapies,” said Dr. Cameron Turtle of Fred Hutchinson Cancer Research Center.
But most of these patients, who were enrolled in a small, early-phase trial, saw their advanced tumors shrink or even disappear after an infusion of genetically engineered immune cells. Turtle, one of the study’s leaders, first presented these results in December at the annual meeting of the American Society of Hematology in San Diego.
In the trial, participants’ disease-fighting T cells were removed from their blood and genetically engineered in a lab at Fred Hutch to produce an artificial receptor, called a CAR, or chimeric antigen receptor, that empowered them to recognize and destroy cancer cells bearing a target molecule called CD19. After patients received chemotherapy, the CAR T cells were infused back into their bloodstream to kill their CD19-positive cancers.
While all 24 patients with chronic lymphocytic leukemia, or CLL, received the experimental therapy, the study authors focused on the results in a subgroup of 19 patients who received particular chemotherapy regimens and doses of CAR T cells the researchers now prefer, based on recent data in other groups of patients on the trial.
Fourteen of 19 experienced a partial or complete regression of their disease in their lymph nodes. And of the 17 who had leukemia in their bone marrow when they enrolled on the trial, the marrow became cancer-free in 15 after they received CAR T cells.
“It’s very pleasing to see patients with refractory disease respond like this,” Turtle said. The research team “had seen very good responses [to the same CAR T-cell therapy] in acute lymphoblastic leukemia and non-Hodgkin lymphoma, so we hoped responses would be good in CLL too.”