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Shakes -
There is also a learning curve with newly approved drugs. I work with a fairly new type of cancer therapy - immunotherapy. Immune response modifiers were tested in humans using the same methods that traditional pharmaceuticals are tested in order to receive FDA approval: Phase I trials were done to determine Maximum Tolerated Dose(MTD); then Phase II trials to determine response in different tumour types;and finally Phase III randomized trials, comparing the new agent with established therapies.
What they have found with immunotherapy is the concept of Maximum Dose doesn't work - that much lower doses than the MTD's get job done with out all the life-threatening toxicities.
When Il-2 was approved by the FDA - the approved dose put 80% of all patients into the ICU and there was a 4% death rate along with the 4% complete response rate. A really tough sell to the average community oncologist who doesn't practice near a Comprhensive Cancer Center.
Now - five years later - the drug is widely used but no one is using the approved dosage (outside of Boston). Instead, most are using greatly modified doses which allow safe outpatient therapy and increased response rates.
My point is, we found this out in *human* patients - using an approved drug. Our mistake was in thinking that the drug would have the same characteristics as chemotherapy drugs (The higher the dose administered - the better - thats how it worked in animal trials). It doesn't work that way in humans, but the experience had to be gained before the lesson could be learned.
Perhaps this is one of the risks we have to take when we are dealing with life threatening illnesses like cancer and HIV. Physicians have a lot of leeway to use approved drugs as they see fit - the best use usually comes with widespread experience.
Bonnie
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