Breast: Hormonal Therapy & Immunotherapy

Approach

• Prophylactic Hormonal Therapy
  • Indication: Age ≥ 35 Years with Life Expectancy ≥ 10-Years &:
    • ≥ 1.7% Five-Year Risk of Breast Cancer
    • Atypical Hyperplasia (ALH/ADH)
    • History of LCIS
    • History of Thoracic Radiation Exposure Before Age 30 Years
  • Duration: Generally Given for 5 Years
  • Choice of Agent: Tamoxifen Generally Preferred
    • Consider Aromatase Inhibitor Instead in Postmenopausal Women Based Largely on Side Effect Profile
• Adjuvant Hormonal Therapy
  • Indication: ER+ Breast Cancer
  • Choice of Agent:
    • Aromatase Inhibitor:
      • Postmenopausal
      • Age ≤ 35 Years
      • High-Risk Features
    • Selective Estrogen Receptor Modulator:
      • Male Sex
      • Aromatase Inhibitor Not Indicated (> 35 Years, Premenopausal with No High-Risk Features)

Selective Estrogen Receptor Modulator (Tamoxifen)

• Mechanism of Action: Selective Estrogen Receptor Modulator (SERM)
• Side Effects:
  • Venous Thromboembolism (VTE) (1%)
  • Endometrial Cancer (0.1%)
  • Cataract (Rare)
• Decreased Risk:
  • Osteoporosis
  • Bone Fracture

Aromatase Inhibitors (Anastrozole, Exemestane or Letrozole)

• Mechanism of Action: Aromatase Inhibitor (Blocks Peripheral Testosterone Conversion to Estrogen)
• Generally Preferred Over Tamoxifen – Better Tolerated
• Side Effects:
  • Osteoporosis Mn
  • Bone Fracture
• Decreased Risk:
  • Venous Thromboembolism (VTE)
  • Endometrial Cancer