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

General principle:
Begin endocrine therapy only when its biologic trigger appears — biochemical recurrence, measurable receptor-positive disease, or symptom-producing tumor burden. Overtreatment wastes QoL; late treatment costs control.

Breast cancer

  • Adjuvant (after surgery): start within 12 weeks post-operation.

  • Neoadjuvant: start after biopsy confirmation ER/PR +, for 3–6 months to shrink the tumor.

  • Metastatic: start promptly at diagnosis unless there’s visceral crisis (then use chemotherapy first).

  • Switch or combine (AI → SERD ± CDK4/6) on progression or ESR1 mutation.

Prostate cancer

Setting Trigger Start rule
Localized high-risk + RT Before RT 2–3 months prior → continue during and after
Locally advanced/metastatic At diagnosis Immediate ADT ± AR antagonist
Biochemical recurrence PSA > 0.4 after prostatectomy or doubling time < 6 mo Early ADT improves MFS; may delay for slow PSA rise & asymptomatic

Clinical caution: confirm true biochemical failure (exclude lab noise or infection).
Quality of life: weigh bone, libido, and metabolic impact before early initiation.

(NCCN Breast 2025; ESMO Prostate 2024)