Preliminary studies show a vaccine made with leukemia cells may be able to prevent a relapse in some chronic myeloid leukemia (CML) patients taking the drug Gleevec.
“Should this vaccine approach prove to be successful, the ability to get patients off lifelong Gleevec therapy would be a significant advance,”says Hyam Levitsky, M.D., professor of oncology, medicine and urology at the Johns Hopkins Kimmel Cancer Center in Baltimore, MD.
Gleevec is one of the first targeted cancer therapies with wide success in CML patients. It destroys most leukemic cells in the body, but some residual cancerous cells are left behind and have been a source of relapse in some patients, especially if Gleevec therapy is stopped.
The study vaccine is made from cancer cells exposed to radiation to stop them from being cancerous and then genetically altered to produce an immune system stimulator called GM-CSF, the researchers said. It was given to 19 CML patients with measurable cancer cells, who were also taking Gleevec therapy for at least one year. After 72 months, the number of remaining cancer cells declined in 13 patients, and vanished in seven patients. The study drug produced relatively few side effects.
There is a caveat. Researchers can’t be sure the results were actually caused by the study vaccine because of the few number of patients participating and there was no alternative treatment used for comparison.
“We want to get rid of every last cancer cell in the body, and using cancer vaccines may be a good way to mop up residual disease,” Dr. Levitsky said.
The challenge is most CML patients face lifelong Gleevec therapy. More than 90 percent achieve remission, but 10 to 15 percent can’t tolerate the drug long term, and secondary drugs produce significant side effects which affect quality of life, the researchers said.
Additionally, Gleevec cannot be taken during pregnancy. Since one-third of CML patients are in their 20s and 30s, many patients hoping to start families would like to stop taking it.
The study, funded by the National Institutes of Health, was published in the January 1, 2010 issue of Clinical Cancer Research.