Carcinoma in situ outcomes in National Surgical Adjuvant Breast and Bowel Project Breast Cancer Chemoprevention Trials

Abstract

Background: In the National Surgical Adjuvant Breast and Bowel Project (NSABP) Breast Cancer Prevention Trial (BCPT), the reduction in risk of noninvasive breast cancer was 50%. There were 93 cases in women receiving placebo and 60 in those receiving tamoxifen (P = .008). Through 7 years of follow-up, the cumulative incidence of noninvasive breast cancer among the placebo group was 15.8 per 1000 women vs 10.2 per 1000 women in the tamoxifen group. In the initial report of the Study of Tamoxifen and Raloxifene (STAR trial), the rate for noninvasive breast cancer was 1.51 per 1000 women assigned to tamoxifen and 2.11 per 1000 women assigned to raloxifene (risk ratio, 1.40; 95% confidence interval = 0.98 to 2.00).

Methods: Additional follow-up of the NSABP STAR trial through March 31, 2009 is reported with a focus on noninvasive breast cancer events.

Results: Through 81 months of median follow-up in the NSABP STAR trial, there are 137 cases of noninvasive breast cancer in the raloxifene group compared with 111 cases in the tamoxifen group (risk ratio = 1.02, 95% confidence interval = 0.61 to 1.70). The occurrence of ductal carcinoma in situ with raloxifene was seen more frequently among women with lower baseline Gail scores and no atypical hyperplasia than in women taking tamoxifen therapy. Raloxifene retained 76% of the effectiveness of tamoxifen in preventing invasive breast cancer.

Conclusions: Although these data indicate that raloxifene offers less protection than tamoxifen for postmenopausal women who are at increased risk for both invasive and noninvasive breast cancer, the favorable risk-benefit profile for raloxifene affords acceptable clinical reduction in the risk of in situ cancers among postmenopausal women.

Figure 1

Cumulative incidence of non-invasive breast cancer in the NSABP Study of Tamoxifen and Raloxifene trial through 81 months of median follow-up, NSABP STAR (P-1).