Effects of tamoxifen on benign breast disease in women at high risk for breast cancer.
BACKGROUND
In 1998 the National Surgical Adjuvant Breast and Bowel Project (NSABP) demonstrated that tamoxifen treatment reduced the incidence of both invasive and noninvasive breast cancer in women at high risk for the disease. We examined the effect of tamoxifen treatment on the incidence of benign breast disease and the number of breast biopsies in the same group of women.


METHODS
We examined the medical records of 13 203 women with follow-up who participated in the NSABP Breast Cancer Prevention Trial. Included in this analysis were women who had undergone a breast biopsy and who had histologic diagnoses of adenosis, cyst, duct ectasia, fibrocystic disease, fibroadenoma, fibrosis, hyperplasia, or metaplasia. The relative risk (RR) for each histologic diagnosis was estimated for women who received tamoxifen and for women who received placebo. We also tallied the number of biopsies that women in the placebo and tamoxifen groups underwent.


RESULTS
Overall, tamoxifen treatment reduced the risk of benign breast disease by 28% (RR = 0.72, 95% confidence interval [CI] = 0.65 to 0.79). Tamoxifen therapy resulted in statistically significant reductions in the risk of adenosis (RR = 0.59, 95% CI = 0.47 to 0.73), cyst (RR = 0.66, 95% CI = 0.58 to 0.75), duct ectasia (RR = 0.72, 95% CI = 0.53 to 0.97), fibrocystic disease (RR = 0.67, 95% CI = 0.58 to 0.77), hyperplasia (RR = 0.60, 95% CI = 0.50 to 0.71), and metaplasia (RR = 0.51, 95% CI = 0.41 to 0.62). Tamoxifen therapy also reduced the risk for fibroadenoma (RR = 0.77, 95% CI = 0.56 to 1.04) and fibrosis (RR = 0.86, 95% CI = 0.72 to 1.03). Compared with the placebo group, the tamoxifen group had 29% (95% CI = 23% to 34%) fewer biopsies (1048 versus 1469) and 19% fewer women who underwent a biopsy (811 versus 1019). This resulted in a 29% reduction in the risk of biopsy in women treated with tamoxifen (RR = 0.71, 95% CI = 0.66 to 0.77). This risk reduction occurred predominantly in women younger than 50 years.


CONCLUSIONS
Women in this study who received tamoxifen, especially younger women (i.e., <50 years), had a reduced incidence of clinically detected benign breast disease and underwent fewer breast biopsies.
Tan-Chiu
Elizabeth
E
Cancer Research Network, 350 84th Avenue, Suite 305, Plantation, FL 33324, USA. tan-chiu@att.net
Wang
Jiping
J
Costantino
Joseph P
JP
Paik
Soonmyung
S
Butch
Cheryl
C
Wickerham
D Lawrence
DL
Fisher
Bernard
B
Wolmark
Norman
N
D000328:Adult; D000367:Age Factors; D016588:Anticarcinogenic Agents / Q000627:therapeutic use*; D001706:Biopsy / Q000706:statistics & numerical data*; D001941:Breast Diseases / Q000188:drug therapy* / Q000473:pathology; D001943:Breast Neoplasms / Q000473:pathology / Q000517:prevention & control*; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D020847:Estrogen Receptor Modulators / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008875:Middle Aged; D018570:Risk Assessment; D012307:Risk Factors; D013629:Tamoxifen / Q000627:therapeutic use*
D016588:Anticarcinogenic Agents; D020847:Estrogen Receptor Modulators; D013629:Tamoxifen