CANTON,OhioOccult micrometastases may still be present after
the standard 5 years of tamoxifen adjuvant hormonal treatment for
patients with stage I or II breast cancer and receptor-positive
tumors. Some of those micrometastases may be estrogen- or
tamoxifen-sensitive, stated Terry Mamounas, MD, adding that this is a
major reason the National Surgical Adjuvant Breast and Bowel Project
(NSABP) has undertaken clinical trial NSABP B-33. The trial will
compare 2 years of exemestane (Aromasin) to 2 years of placebo in
postmenopausal, estrogen receptor-positive stage I-II breast cancer
patients who are disease free after being on tamoxifen (Nolvadex) for
Mamounas, Medical Director at Aultman Cancer Center in Canton, Ohio,
discussed the B-33 trial design (see Figure) at a clinical
investigators workshop sponsored by the University of Texas M.
D. Anderson Cancer Center and Pharmacia Oncology.
Study Aims and Design
The primary aim of this study is to determine whether adjuvant
exemestane after 5 years of tamoxifen prolongs disease-free survival
vs placebo, Dr. Mamounas said. Secondary aims are to
determine whether adjuvant exemestane prolongs overall survival vs
placebo and to evaluate the effect of exemestane and of tamoxifen
withdrawal on bone mineral density.
The protocol design calls for enrollment of 3,000 patients, which is
anticipated to require 40 months. The study is designed to have an
80% power to detect a 21% reduction in hazard rate and assumes that
50% of patients will be node-negative.