Leuprolide is a safe and effective treatment of estrogen receptor-positive premenopausal breast cancer. Data from the SOFT/TEXT trials solidified leuprolide in combination with an aromatase inhibitor as an effective hormonal treatment for premenopausal breast cancer. However, the efficacy of monthly leuprolide depot compared to leuprolide depot every 3 months in combination with an aromatase inhibitor in this patient population is unclear.

In this single center retrospective study, 201 patients were enrolled between January 1, 2015, and October 1, 2016; 100 were included in the 7.5 mg leuprolide monthly injection plus aromatase inhibitor group and 101 in the 22.5 mg leuprolide injection every 3 months plus aromatase inhibitor group. The primary end point was the proportion of patients who experienced ovarian ablation, defined as an estradiol concentration less than 40 pg/mL and a follicle-stimulating hormone concentration of 23 to 116 mU/mL after 3 months of treatment. Significance threshold was P < .05 (2 sided). Secondary end points included disease-free survival and overall survival at 1-year follow-up, as well as adverse events reported during treatment.

All patients in the monthly leuprolide arm experienced ovarian ablation compared to 100 (99%) of 101 patients in the arm treated every 3 months (P = 1). The disease-free survival rate at 1 year was 95% in the monthly leuprolide arm and 97% in the arm treated every 3 months (P = .75). The overall survival rate at 1 year was 100% in the monthly leuprolide arm and 99% in the arm treated every 3 months (P = 1). The most common treatment-related adverse events between the 2 groups were musculoskeletal pain, hot flashes, fatigue, and insomnia.

Leuprolide acetate depot administered every 3 months is as efficacious and tolerable as a monthly injection in combination with an aromatase inhibitor for premenopausal patients with hormone receptor-positive breast cancer.