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

Why gaps happen: toxicity, logistics, patient choice, comorbid events.
Goal: restart effectively without hormone flare or resistance.

Restart rules

Drug Class Restart note
GnRH agonists Re-induce slowly; use short anti-androgen cover for 2 weeks.
GnRH antagonists Immediate re-suppression — safe restart any time.
AIs/SERDs Restart same agent if pause < 8 weeks and no progression; otherwise switch class.
Tamoxifen Restart with anticoagulation review if prior VTE.

Bridging periods

  • Use short-acting LHRH analogs or low-dose steroids to maintain partial suppression.

  • Keep DEXA monitoring if gap > 6 months.

Communication tip: document “treatment holiday” reason and planned re-evaluation date in chart and discharge summary.