Cancer Prevention Trials

The Clinical Trials Unit (CTU) at Cancer Care Manitoba has been actively involved in conducting cancer prevention trials since 1992. Women in Manitoba are playing a major role in finding ways to reduce the risk of developing breast cancer in high risk women. These women are paving the way for future generations and help to place CCMB at the forefront of research in breast cancer prevention. The three prevention trials we have participated in are outlined below:


Breast Cancer Prevention Trial (BCPT) in the 1990's looked at Tamoxifen for preventing breast cancer. Manitoba accrued 140 of the 13,388 women. Study results in April 1998 showed a 49 % reduction in breast cancer among the high risk women who took Tamoxifen.


STAR, a Study of Tamoxifen and Raloxifene. Manitoba accrued 139 of the 19,490 women. Results in April 2010 indicated that raloxifene retained 76% of the effectiveness in preventing invasive disease and grew closer to tamoxifen in preventing noninvasive disease, while remaining less toxic. Tamoxifen remains superior to raloxifene in reducing the risk of both invasive and non-invasive breast cancer among postmenopausal women at increased risk.


This trial was designed to determine if Exemestane can prevent breast cancer in healthy postmenopausal women at increased risk for developing breast cancer. Manitoba accrued 103 of the 4560 women. Trial results released in June2011 demonstrated a 65 % relative reduction in the incidence of invasive breast cancer compared to the placebo control with no serious toxicity and minimal quality of life differences. This is a significant improvement over Tamoxifen and raloxifene, which had been used for breast cancer prevention. Both reduced breast cancer incidence by about 50% but had significant side effects and therefore had been little used in this preventative role.


In May 2016, CCMB, in collaboration with MAYO Clinic Rochester, opened the GENRE breast cancer prevention study. The GENRE study is a pilot study to determine if a polygenic risk score influences the decision to accept breast cancer preventative medications (Tamoxifen, Raloxifene, or Exemestane) amongst non-BRCA women at risk. CCMB has now been involved with the first clinical trial of polygenic risk score (PRS) in the world. There was an overwhelming interest in the GENRE study. CCMB quickly met the accrual target of 75 patients in 18 months. Results of this study at not yet known.