Anti-Estrogen Withdrawal Effect With Raloxifene? A Case Report

Area of Science:

• Oncology
• Endocrinology

Background:

• A 66-year-old patient with metastatic estrogen and progesterone receptor-positive, Her-2/neu-negative breast cancer presented with advanced disease, including bone, pulmonary, and hepatic metastases.
• The patient had a history of raloxifene use for approximately 8 years.

Observation:

• Following raloxifene discontinuation, the patient experienced rapid improvement in clinical parameters and symptoms, including resolution of dyspepsia and diarrhea.
• Despite the treating oncologist initially deeming an anti-estrogen withdrawal effect (AEWE) implausible, the patient's condition continued to improve significantly.

Findings:

• The patient achieved lasting regression of hepatic metastases and remained asymptomatic with a good performance status for over 16 months without oncological therapy.
• This sustained remission following raloxifene withdrawal suggests a potential raloxifene rebound effect, also known as an anti-estrogen withdrawal effect (AEWE).

Implications:

• This case underscores the necessity of screening breast cancer patients, particularly those with advanced or recurrent disease using raloxifene or similar selective estrogen receptor modulators (SERMs) like tamoxifen, for the possibility of an AEWE.
• Further investigation into AEWE as a potential therapeutic mechanism in metastatic breast cancer is warranted.