Medications used for breast cancer risk reduction: A brief summary of clinical trials
| Trial | N | Eligibility | HRa | HRb | NNT |
|---|---|---|---|---|---|
| NSABP P-1 5-year trial Tamoxifen 20 mg vs placebo33 | 13, 388 | Pre- and post-menopausal; Gail model-estimated 5-year risk ≥ 1.66% | 0.51 | 0.14 for AH; 0.44 for LCIS | 22 |
| IBIS-1 5-year trial Tamoxifen 20 mg vs placebo48 | 7,154 | Pre- and post- menopausal; 50% on hormone-replacement therapy | 0.75; with long-term follow-up 0.71 | Not stated | Not stated |
| STAR P-2 5-year trial Tamoxifen 20 mg vs raloxifene 60 mg34,50 | 19,747 | Postmenopausal | Equal at 5 years; with long-term follow-up; raloxifene = 0.62 | Equal | Not stated (about 22) |
| MAP.3 3-year trial Exemestane 25 mg, exemestane 25 mg plus celecoxib, vs placebo46 | 4,560 | Postmenopausal | 0.35 | 0.36 (for AH/LCIS combined) | 26 at 5 years |
| IBIS II 5-year trial Anastrozole 1 mg vs placebo47 | 3,864 | Postmenopausal | 0.47 | 0.31 (for AH/LCIS combined) | 29c |
| Low-dose tamoxifen 3-year trial Tamoxifen 5 mg vs placebo49 | 500 | Pre- and post menopausal; included patients with ductal carcinoma in situ | 0.48 | Not stated | 22 |
↵a For reduction in invasive breast cancer.
↵b For reduction in invasive breast cancer in patients with AH and LCIS.
↵c To prevent 1 cancer in 7 years of follow-up, 36 women would need to be treated.
AH = atypical hyperplasia; HR = hazard ratio; IBIS = International Breast Cancer Intervention Study; LCIS = lobular carcinoma in situ; MAP = Mammary Prevention trial; NNT = number needed to treat; NSABP = National Surgical Adjuvant Breast and Bowel Project; STAR = Study of Tamoxifen and Raloxifene