Because most prostate cancer cells are androgen-dependent, these tumor cells need androgens for “nutrition” to grow.
Androgen deprivation therapy (ADT) is the surgical or pharmacological blockade of androgen nutrition to “starve” prostate cancer cells.
Normal people get 90% of their blood androgens from the testes and another 10% from the adrenal glands.
Surgical removal of the testes, also known as surgical debulking, eliminates most of the source of androgens and reduces serum testosterone to less than 5% to 10% of its original level, while dihydrotestosterone (DHT), the active androgen inside the prostate that maintains tumor cell growth, is reduced by only about half, leaving about 40% of DHT in the prostate. The DHT in the prostate remains about 40%.
The main source of these androgens is the adrenal glands, so patients still need to take oral anti-androgen drugs (e.g., bicalutamide, flutamide) to block the effects of androgens secreted by the adrenal glands and to maximize the “nutrition” of the tumor cells by androgens for optimal treatment.