Rivizor – A New Third-Generation Aromatase Inhibitor for the Treatment of Advanced Breast Cancer after Tamoxifen Failure

Abstract

Rivizor^TM (vorozole) is a new, highly potent and selective third-generation aromatase inhibitor for treatment of advanced breast cancer. In an open-label study, 30 postmenopausal women failing tamoxifen therapy received Rivizor 2.5 mg once daily until disease progression. Rivizor produced clinical benefit (partial response or no change) in 16 of 27 evaluable patients (59.3%). Five patients (18.5%) had a partial response (UICC criteria) which lasted for a median of 15 months (range 14–42.5 months), 11 patients had disease stabilization for a median of 14 months (7–24 months), and 11 patients had disease progression. Median time to first response was 3.9 months (3–27.5 months): estimated median survival time for all patients was 22.8 months (2–52.8 months) and estimated median time to disease progression was 10.8 months (1.4–42.4 months). Estradiol levels decreased to below limits of detection from 1st month of treatment until study end. Androstenedione, 17α-hydroxyprogesterone, dehydroepiandrosterone, and free-testosterone levels were unaffected by Rivizor. ACTH stimulation tests demonstrated that Rivizor does not interfere with adrenal mineralocorticoid and glucocorticoid steroid synthesis. Adverse events were mild-to-moderate. Rivizor might be an effective and well-tolerated alternative treatment for postmenopausal advanced breast cancer patients following tamoxifen failure.