I am still trying to reconcile the doctor's reccommended "vacation" with the compliance issue as described in the article and some earlier posts. I looked up the FDA approved inserts for the most common AI's, Femara (Letrozole) and Arimidex (Anastrazole). Here is what it says about how long the drug is active in the body when you cease taking it:
Letrozole’s terminal elimination half-life is about 2 days and steady-state plasma concentration after daily 2.5 mg dosing is reached in 2-6 weeks.
The reccomended daily dose, ARIMIDEX 1 mg, reduced estradiol by approximately 70% within 24 hours and by approximately 80% after 14 days of daily dosing. Suppression of serum estradiol was maintained for up to 6 days after cessation of daily dosing with ARIMIDEX 1 mg.
So, if you are on a month's "vacation," you are unprotected for rougly 24 days out of 30. If you take enough "vacations," how does that impact the statistical results you will see?
The fact of the matter is, no one knows what the truly optimum duration of therapy with these agents is. My onc said to me that 5 years of treatment is an arbitrary number based on the arbitrary number of 5 years used in trials. When issues arose about the potential for exended therapy, he said to me, the drug manufacturers were probably saying to themselves, "Dang, we should have gone for 10 years from the start!"
These are pills, not magic bullets. They are efficacious and toxic in about half the patients who take them, and just toxic in the other half. It is not unreasonable to balance QOL against the particular risk you are managing in deciding how long to take them.
Hopeful
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