New Clinical Trial to Investigate Treatment Options After Tamoxifen

The National Surgical AdjuvantBreast and Bowel Project(NSABP) has launched a new phase III clinical trial that will evaluateexemestane (Aromasin) in 3,000 postmenopausal women diagnosed with estrogenreceptor-positive breast cancer who have completed 5 years of tamoxifen(Nolvadex) therapy. The trial, protocol B-33, will determine whether exemestanewill prolong disease-free and overall survival in women previously treated forbreast cancer. Over 100 sites in the United States, Canada, and Puerto Rico areexpected to take part in the trial.

Aromatase Inactivator

Exemestane is an oral aromatase inactivator currently approvedfor the treatment of advanced breast cancer in postmenopausal women whose tumorshave stopped responding to tamoxifen. This group of drugs selectively targetsand inactivates the aromatase enzyme, reducing the supply of estrogen tocancerous cells, and thus preventing the cells from continuing to grow.

"This study could potentially ease women’s concernsregarding breast cancer recurrence and what treatment options are availableafter tamoxifen therapy is complete," said Dr. Roy Smith, director ofmedical affairs and oversight at NSABP, and protocol officer for the trial.

A majority of patients treated with tamoxifen are disease-freeafter 5 years of therapy. However, even after several years of tamoxifentherapy, some of these patients harbor small tumor cells that could spread toanother part of the body and cause a recurrence of cancer.

"This trial is unique in that it offers a therapy for womenwho have not had a recurrence of cancer and who have completed standardantiestrogen therapy with tamoxifen," said Dr. Terry Mamounas, trialprotocol chair. "Sequential treatment with exemestane immediately followingtamoxifen therapy may continue to treat hormone-sensitive tumors. Tamoxifen isthe standard adjuvant hormonal therapy for women with breast cancer. However,studies have shown that tamoxifen offers the greatest benefit when taken foronly 5 years."

In the trial, women who have completed 5 years of tamoxifentherapy will be randomly assigned to receive either 25 mg of exemestane dailyfor 2 years or placebo. The most commonly reported side effects associatedwith exemestane include mild to moderate hot flashes, nausea, and fatigue.