Can letrozole increase the rates of breast conserving surgery?

This paper studies the ideal length of time needed for patients to receive letrozole (Femara) treatment to allow for breast conserving surgery.

Neoadjuvant chemotherapy (chemotherapy treatment given before primary treatment) compared with adjuvant chemotherapy (treatment given alongside primary treatment) gives similar survival rates. However, neoadjuvant therapy is associated with increased rates of breast conservation surgery, where only part of the breast tissue is removed, compared to adjuvant therapy. Neoadjuvant endocrine therapy (hormone therapy) has been less well investigated.  

For post-menopausal women with estrogen-receptor positive tumors (when receptors that respond to the female hormone estrogen are present), endocrine therapy is more beneficial. Letrozole (a drug that blocks estrogen activity) is an endocrine therapy that is used to treat breast cancer, typically over a 4 month period. The authors studied the optimal length of letrozole neoadjuvant therapy, such that patients become suitable for breast conservation surgery. 

Postmenopausal women with primary and invasive breast cancer (cancer that has not spread beyond the breast but has the potentially to do so) were eligible. Patients were estrogen receptor and/or progesterone receptor positive (when receptors that respond to the female hormone progesterone are present). They had large tumors and were not initially eligible for breast conserving surgery. Patients were given 2.5 mg letrozole daily for the duration of treatment.

139 patients were included in the final analysis. The percentage of patients who became suitable for breast conserving surgery increased over time, and 66% of patients were eligible by 12 months. At the end of the study, 69% of patients became eligible for breast conserving surgery.

The minimum time to tumor shrinkage sufficient for breast conserving surgery was 7.5 months. Overall, there was an average 75.3% reduction in tumor volume. Nine patients had progressive disease (tumor growth). 101 patients had a partial response/stable disease (tumor shrinkage). Four patients had a complete response (no more cancer cells).

After an average of 3 years of follow up there were a total of 4 cancer-related and 1 non-cancer-related deaths.  In those undergoing mastectomy, 69.2% of patients survived without disease compared to 96.1% of those undergoing breast conserving surgery.

The average treatment duration was 201 days. Letrozole was well tolerated. 61.6% of patients experienced an adverse event (undesired effect from medication including fatigue, headache, dizziness) during the study. 

The authors concluded that extending the duration of letrozole use in neoadjuvant treatment to reduce tumor volume for breast conserving surgery is effective and safe.