Course Content
Module 1 — Principles of Hormone Therapy in Oncology
Mechanism and Dosing Overview Aromatase Inhibitors (AIs): block the enzyme aromatase (CYP19A1), which converts androgens to estrogens in adipose and peripheral tissues. Examples: Anastrozole 1 mg orally daily, Letrozole 2.5 mg orally daily, Exemestane 25 mg orally daily. These are the preferred agents in postmenopausal women with estrogen receptor–positive breast cancer. Selective Estrogen Receptor Modulators (SERMs): such as Tamoxifen 20 mg orally daily — bind the estrogen receptor and act as antagonists in breast tissue but partial agonists in bone and endometrium. Selective Estrogen Receptor Degraders (SERDs): such as Fulvestrant 500 mg intramuscularly on days 0, 14, 28, then every 28 days thereafter — promote estrogen receptor degradation. CYP17 Inhibitors: Abiraterone acetate 1000 mg orally daily on an empty stomach plus Prednisone 5 mg orally twice daily — block the CYP17A1 enzyme, suppressing androgen synthesis in adrenal glands and tumors. Gonadotropin-Releasing Hormone (GnRH) Agonists and Antagonists: Leuprolide 7.5 mg subcutaneously every 4 weeks or depot every 3–6 months; Degarelix 240 mg subcutaneously loading dose, then 80 mg every 4 weeks; Relugolix 120 mg orally daily — suppress testosterone or estrogen production by downregulating or directly blocking pituitary gonadotropin release.
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Hormone Therapy for Cancer Patients: Mechanisms, Indications, and Clinical Practice

Biological synergy

  • Hormone therapy shrinks gland/tumor volume, reducing hypoxia and improving dose conformity.

  • Cell-cycle arrest in G1 enhances radiosensitivity.

  • Micro-environmental effect: decreased VEGF → better perfusion → higher O₂ → ↑ radiation kill.

Clinical evidence

Trial Population Key finding
RTOG 8610 / EORTC 22961 Locally advanced prostate ADT + RT ↑ OS ~20 % vs RT alone
TROG 96.01 Locally advanced prostate 3–6 mo neoadj ADT ↓ biochemical failure
EBCTCG Meta-analysis ER+ breast Endocrine therapy + RT ↓ local recurrence ~ 50 %

Practical integration

Cancer Sequence Duration
Prostate Start ADT 2–3 mo before RT → continue during + 18–36 mo after Long-term for high-risk
Breast RT usually after chemo; endocrine can start concurrently or ≤ 3 weeks post-RT 5–10 y total endocrine

(NCCN Prostate 2025; ESMO Breast 2024)