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Two-Year Z-FAST Trial Shows Zoledronic Acid Prevents Bone Loss in Breast Cancer Patients Taking Letrozole: Presented at SABCS

By Charlene Laino

SAN ANTONIO, TX -- December 18, 2006 -- Concurrent administration of the third-generation bisphosphonate zoledronic acid (Zometa) appears to prevent the bone loss often seen among early stage breast cancer patients on aromatase inhibitor therapy, researchers reported here at the 29^th Annual San Antonio Breast Cancer Symposium (SABCS).

Two-year interim results from the Zometa-Femara Adjuvant Synergy Trial (Z-FAST) indicate that patients who were assigned to intravenous treatment with zoledronic acid 4 mg every 6 months along with 2.5 mg letrozole daily had improvements in bone density measures at key sites.

"At 24 months, upfront zoledronic acid increased lumbar spin bone mineral density 5.9% and total hip bone mineral density by 4.7% compared with patients who were on a delayed start of bisphosphonate therapy," said presenter Adam Brufsky, MD, assistant professor of medicine, Magee-Women's Hospital, University of Pittsburgh Medical Center/University of Pittsburgh Cancer Institute Breast Cancer Program, Pittsburgh, Pennsylvania.

In the Z-FAST study, 301 patients with early stage breast cancer were randomly assigned to receive zoledronic acid at the same time as they initiated treatment with letrozole. A second group of 301 patients were assigned to initiate letrozole alone, and were given zoledronic acid only if they had a marked decreased in bone mineral density as detected in imaging studies, if they had a symptomatic fracture or if they had an asymptomatic fracture by 36 months.

During the first 2 years of therapy, 12.7% of patients in the delayed cohort initiated zoledronic acid, Dr. Brufsky reported in a poster presentation on December 16^th.

At 24 months, the bone mineral density in the lumbar spine had increased by 3% among patients who initiated zoledronic acid at the same time as letrozole; those in the delayed treatment cohort experienced a 2.9% loss in bone mineral density at time point. That 5.9% overall difference reached statistical significance at the P < .0001, he said.

Bone mineral density in the total hip increased by 1.5% at 24 months among patients who initiated therapy with zoledronic acid at the same time as letrozole, while those in the delayed treatment cohort experienced a 3.2% loss at this time point. That 4.7% overall difference reached statistical significance at the P < .001, Dr. Brufsky said.

Clinical fractures occurred in 4.3% of the upfront bisphosphonate treatment group compared with 4% of the patients receiving delayed treatment, a nonsignificant difference, Dr. Brufsky said. "An analysis of fracture rates at 36 months is planned," he said.


[Presentation title: Twenty-Four Month Follow-Up of the Effect Of Zoledronic Acid (ZA) on Aromatase Inhibitor Associated Bone Loss (AIBL) in Postmenopausal Women (PMW) With Early Breast Cancer (BCa) Receiving Adjuvant Letrozole (LET). Abstract 5060]

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