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

Liver toxicity

  • Tamoxifen, Abiraterone, Fulvestrant may elevate transaminases.

    • Monitor LFT baseline + q 3 mo.

    • Hold if AST/ALT > 5× ULN or bilirubin > 3× ULN.

    • Re-challenge at 50 % dose once normalized.

Endocrine cross-effects

  • AI → ↓ estrogen → ↑ LDL, hot flushes.

  • Abiraterone → ↑ mineralocorticoids → HTN, hypokalemia.

  • Long ADT → ↑ insulin resistance + ↑ fat mass + ↓ Hb → check Hb annually.

  • Consider intermittent ADT to limit metabolic drift.

Rare events

Agent Rare effect Action
Tamoxifen Endometrial carcinoma Report post-menopausal bleeding; pelvic US q year if symptomatic
SERD Injection-site necrosis (rare) Rotate gluteal sites
GnRH antagonist Injection reaction Ice pack ± NSAID pre-dose
Abiraterone Adrenal insufficiency if prednisone stopped Re-start prednisone, monitor cortisol