Ovarian Ablation / Suppression (OAS)

Definition

Ovarian Ablation/Suppression (OAS) is a therapeutic strategy aimed at eliminating or reducing estrogen production from the ovaries in premenopausal women with hormone receptor–positive (HR⁺) breast cancer.

• Ablation = permanent loss of ovarian function
• Suppression = reversible temporary shutdown of ovarian function

Rationale in Breast Cancer

• In premenopausal women, estrogen is primarily produced by the ovaries and drives the growth of ER⁺ breast tumors.
• OAS reduces circulating estrogen to postmenopausal levels, improving the efficacy of endocrine therapy (e.g., tamoxifen, aromatase inhibitors).
• Shown to improve disease-free survival (DFS) and overall survival (OS) when combined with other hormonal treatments in certain high-risk patients.

Methods of OAS

1. Drug Choice
   • LHRH agonists (goserelin, leuprolide) are the mainstay for reversible suppression.
   • Dosing:
     • Goserelin: 3.6 mg SC monthly or 10.8 mg SC every 3 months
     • Leuprolide: 7.5 mg IM monthly or long-acting forms every 3 months
   • Use with tamoxifen or aromatase inhibitor (AI; only effective if ovarian function is fully suppressed).
2. Combination Strategies
   • Tamoxifen + OAS: Standard for high-risk premenopausal women.
   • AI + OAS: For very high-risk patients or recurrence prevention — AI alone is ineffective in premenopause without OAS.
3. Treatment Duration
   • Usually 5 years (can extend to 7–10 years in very high risk).
   • OAS itself may be given for 2–5 years depending on recurrence risk.
4. Monitoring
   • Confirm estradiol levels if using AI to ensure complete suppression.
   • Monitor bone mineral density — OAS accelerates bone loss.
   • Manage menopausal symptoms (hot flashes, vaginal dryness).
5. Side Effects
   • Menopausal symptoms (vasomotor, sexual dysfunction)
   • Bone loss → osteoporosis risk
   • Mood changes
   • Injection site reactions (for LHRH agonists)