Tamoxifen and Breast Cancer Incidence Among Women With Inherited Mutations in BRCA1 and BRCA2: National Surgical Adjuvant Breast and Bowel Project (NSABP-P1) Breast Cancer Prevention Trial
2001
ContextAmong cancer-free women aged 35 years or older, tamoxifen reduced the
incidence of estrogen receptor (ER)–positive but not ER-negative breast
cancer. The effect of tamoxifen on breast cancer incidence among women at
extremely high risk due to
inheritedBRCA1 or BRCA2mutations is unknown.ObjectiveTo evaluate the effect of tamoxifen on incidence of breast cancer among
cancer-free women with
inherited BRCA1 or BRCA2 mutations.Design, Setting, and ParticipantsGenomic analysis of BRCA1 and BRCA2
for 288 women who developed breast cancer after entry into the
randomized, double-blind Breast Cancer Prevention Trial of the National Surgical
Adjuvant Breast and Bowel Project (between April 1, 1992, and September 30,
1999).Main Outcome MeasureAmong women with BRCA1 or BRCA2 mutations, incidence of breast cancer among those who were receiving
tamoxifen vs incidence of breast cancer among those receiving placebo.ResultsOf the 288 breast cancer cases, 19 (6.6%) inherited disease-predisposing BRCA1 or BRCA2 mutations. Of 8
patients with BRCA1 mutations, 5 received tamoxifen
and 3 received placebo (risk ratio, 1.67; 95% confidence interval, 0.32-10.70).
Of 11 patients with BRCA2 mutations, 3 received tamoxifen
and 8 received placebo (risk ratio, 0.38; 95% confidence interval, 0.06-1.56).
From 10 studies, including this one, 83% of BRCA1
breast tumors were ER-negative, whereas 76% of BRCA2
breast tumors were ER-positive.ConclusionTamoxifen reduced breast cancer incidence among healthy BRCA2 carriers by 62%, similar to the reduction in incidence of ER-positive
breast cancer among all women in the Breast Cancer Prevention Trial. In contrast,
tamoxifen use beginning at age 35 years or older did not reduce breast cancer
incidence among healthy women with inherited BRCA1
mutations. Whether tamoxifen use at a younger age would reduce breast cancer
incidence among healthy women with BRCA1 mutations
remains unknown.
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