In the January issue of Blood, a study shows that in rare cases of chronic myelogenous leukemia (CML), treatment with Gleevec can be discontinued.
The researchers think that some patients treated with Gleevec (imatinib mesylate) that go into extended remissions can stop the drug. They add that patients continue strict monitoring for relapse.
Twelve patients were put into remission with Gleevec for over two years. Six of these patients experienced a relapse within five months after being taken off the drug. When Gleevec was restarted, residual disease again declined.
The other six patients remain in remission after nine to twenty four months follow up.
Despite these results the researchers say 'we do not widely recommend imatinib discontinuation at the present time".
I do have a few questions myself that the article did not address:
Does Gleevec have severe side effects that warrants stopping it at all?
Do they think that Gleevec can potentially cure the patient and some might be able to stop treatment all together?
1. I would ask that question too, and a few others. Some tumors are highly resistant to virtually all anti-cancer drugs, while other tumors are quite sensitive. Breast, prostate, and ovarian cancers represent malignancies in which the development of drug-resistant forms has prevented significant cures with current conventional chemotherapeutic agents. A high degree of drug resistance is also associated with cancers of the liver, colon, pancreas, kidney, and lung. Ninety percent of all drug cures occur in only ten percent of cancer types that are intrinsically drug-sensitive, e.g., leukemias, testicular cancer, and Hodgkin's disease. And with those, the dosages must be fairly high. You can test Gleevec at a sufficiently high concentration that it will kill virtually anthing. But at what price, the patient's life?
M.D. Anderson studies (published in the June 29, 2006 issue of the journal Circulation) have shown that Gleevec can cause heart failure. Possible solutions suggested by them include avoiding certain drugs, lowering drugs dosages, administering drugs slower and over a longer period of time, monitoring cardiac health more stringently, avoid giving some drugs simultaneously, treating cardiac risk factors, use of an echocardiogram during and after cancer treatment, and treating patients with heart failure drugs.
It is not known why Gleevec (and most other drugs) either works or doesn't work. There is so much about drug activity that is thought to be known but in reality, is not. Drug resistance/drug response is multifactorial. It matters not that a particular molecular target is present, if the drug can't even get into the cell to interact with that target, or if it gets in but is metabolized or actively extruded out of the cell (common mechanism of drug resistance). The good news is that we can measure the net result of everything (that it worked or didn't work), but the bad news is we don't know why it worked or why it didn't work.
Posted at 5:17PM on Feb 12th 2007 by Gregory D. Pawelski