6/28/23, 11:22 PM NSABP P-1 Pathway Feedback Search Clinical Topics Home Studies NSABP P 1 NSABP P 1 Trial question What is the role of tamoxifen in patients who were at increased risk for breast cancer? Study design Multi-center Double blinded RCT Population 13388 female patients Inclusion criteria: women who were at increased risk for breast cancer Key exclusion criteria: pregnancy, clinical evidence of breast cancer, receipt of estrogen or progesterone replacement therapy, oral contraceptives, or androgens within 3 months before randomization; and a history of deep vein thrombosis or PE Interventions N=6681 tamoxifen (20 mg/day for 5 years) N=6707 placebo (matching placebo daily for 5 years) Primary outcome Invasive breast cancer 43.4 43.4 32.5 21.7 22 10.8 Significant decrease 0.0 Tamoxifen Placebo Significant decrease in invasive breast cancer (22 vs. 43.4; RR 0.51, 95% CI 0.39 to 0.66) Secondary outcomes Significant decrease in noninvasive breast cancer (7.7 vs. 15.9; RR 0.5, 95% CI 0.33 to 0.77) https://web.pathway.md/studies/recap4ZINfl9MGXFf 1/2 6/28/23, 11:22 PM NSABP P-1 Pathway Safety outcomes Significant differences in endometrial cancer (2.30 vs. 0.91 per 1,000; RR 2.53, 95% CI 1.35-4.97), stroke (1.45 vs. 0.92 per 1,000 women), PE (0.69 vs. 0.23 per 1,000 women), and deep vein thrombosis (1.34 vs. 0.84 per 1,000 women). Conclusion In women who were at increased risk for breast cancer, tamoxifen was superior to placebo with respect to invasive breast cancer. Reference Fisher B, Costantino JP, Wickerham DL et al. Tamoxifen for prevention of breast cancer: report of the National Surgical Adjuvant Breast and Bowel Project P-1 Study. J Natl Cancer Inst. 1998 Sep 16;90(18):1371-88. Open reference URL https://web.pathway.md/studies/recap4ZINfl9MGXFf 2/2