PROSTATE CANCER TREATMENT: DRUGS THAT BLOCK THE EFFECTS OF HORMONES AT THE PROSTATE
Antiandrogens
These drugs don’t care how much LHRH, LH, FSH, testosterone, or DHT you make; it doesn’t matter to them. (Actually, antiandrogens cause testosterone levels to go up because of an increase in LH.) All they do is make sure testosterone and DHT don’t reach their targets—the receptors. In other words, antiandrogens act as dummy keys in the “locks,” or receptors. When testosterone and DHT reach the receptors, there’s already a key sitting in the lock—so they can’t enter the lock and activate the receptors. Therefore, the tumor doesn’t get the hormones it needs to nourish its androgen-dependent cells.
Flutamide is the most widely used anti-androgen. Casodex, a new, not-yet-approved drug, is another; so is cyproterone acetate, an antiandrogen that’s used in Europe but is not yet approved in this country.
Their potential advantage is that, because testosterone is not suppressed, they preserve potency. In men taking flutamide, for example, 87 percent remain potent. (This is not true, however, for cyproterone acetate. This drug, like estrogen, also suppresses the hypothalamus-pituitary connection—so it lowers LH, which affects testosterone production. Thus, it does produce impotence.)
But do antiandrogens work? The answer, for now, is probably not enough when they’re used by themselves. They also produce breast enlargement in 74 percent of the men who take them.
In total androgen blockade (see below), flutamide is given along with an LHRH agonist. In new research, scientists are looking into combining flutamide with something else—perhaps finasteride (discussed later in this chapter) to increase its effectiveness.
Side effects: Flutamide’s major side effect is diarrhea. Also, it can cause significant liver damage in some men; therefore, it’s a good idea for men taking flutamide to have their liver function checked after the first few months of treatment.
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