The National Surgical Adjuvant Breast and Bowel Project (NSABP) has launched a new phase III clinical trial that will evaluate exemestane(Drug information on exemestane) (Aromasin) in 3,000 postmenopausal women diagnosed with estrogen receptor-positive breast cancer who have completed 5 years of tamoxifen(Drug information on tamoxifen) (Nolvadex) therapy. The trial, protocol B-33, will determine whether exemestane will prolong disease-free and overall survival in women previously treated for breast cancer. Over 100 sites in the United States, Canada, and Puerto Rico are expected to take part in the trial.
Exemestane is an oral aromatase inactivator currently approved for the treatment of advanced breast cancer in postmenopausal women whose tumors have stopped responding to tamoxifen. This group of drugs selectively targets and inactivates the aromatase enzyme, reducing the supply of estrogen to cancerous cells, and thus preventing the cells from continuing to grow.
"This study could potentially ease women’s concerns regarding breast cancer recurrence and what treatment options are available after tamoxifen therapy is complete," said Dr. Roy Smith, director of medical affairs and oversight at NSABP, and protocol officer for the trial.
A majority of patients treated with tamoxifen are disease-free after 5 years of therapy. However, even after several years of tamoxifen therapy, some of these patients harbor small tumor cells that could spread to another part of the body and cause a recurrence of cancer.
"This trial is unique in that it offers a therapy for women who have not had a recurrence of cancer and who have completed standard antiestrogen therapy with tamoxifen," said Dr. Terry Mamounas, trial protocol chair. "Sequential treatment with exemestane immediately following tamoxifen therapy may continue to treat hormone-sensitive tumors. Tamoxifen is the standard adjuvant hormonal therapy for women with breast cancer. However, studies have shown that tamoxifen offers the greatest benefit when taken for only 5 years."
In the trial, women who have completed 5 years of tamoxifen therapy will be randomly assigned to receive either 25 mg of exemestane daily for 2 years or placebo. The most commonly reported side effects associated with exemestane include mild to moderate hot flashes, nausea, and fatigue.