Abstract
Breast carcinoma is the most common malignancy among women and it has a major impact on mortality. Studies of primary chemoprevention with tamoxifen have generated high expectations and considerable success rates. The efficacy of lower doses of tamoxifen is similar to that seen with a standard dose of the drug, and there has been a reduction in healthcare costs and side effects.The immune reaction to monoclonal antibody Ki-67 (MIB-1) and the expression of estrogen receptors (1D5) and progesterone receptors (PgR 636) in breast carcinoma were studied in patients treated with 10 mg of tamoxifen for a period of 14 days.A prospective randomized clinical trial was conducted with 38 patients divided into two groups: Group A: N = 20 (control group-without medication) and Group B: N = 18 (tamoxifen/10 mg/day for 14 days). All patients signed an informed consent term previously approved by both institutions. Patients underwent incisional biopsy before treatment and 14 days later a tumor tissue sample was obtained during surgical treatment. Positivity was quantitatively assessed, counting at least 1.000 cells per slide. For statistical data analysis, a Wilcoxon non-parametric test was used, and α was set at 5%.Both groups (A and B) were considered homogeneous regarding control variables. In Group A (control), there was no statistically significant reduction in Ki-67 (MIB-1) (p = 0.627), estrogen receptor (1D5) (p = 0.296) and progesterone receptor positivity (PgR 636) (p = 0.381).In Group B (tamoxifen 10 mg/day), the mean percentage of nuclei stained by Ki-67 (MIB-1) was 24.69% before and 10.43% after tamoxifen treatment. Mean percentage of nuclei stained by estrogen receptor (1D5) was 59.53% before and 25.99% after tamoxifen treatment. Mean percentage of nuclei stained by progesterone receptor (PgR 636), was 59.34 before and 29.59% after tamoxifen treatment. A statistically significant reduction was found with the three markers (p < 0.001).Tamoxifen significantly reduced monoclonal antibody Ki-67 (MIB-1), estrogen receptor (1D5) and progesterone receptor positivity (PgR 636) in the breast epithelium of carcinoma patients treated with a 10 mg dose of tamoxifen for 14 days.
Highlights
Chemoprophylaxis of breast carcinoma with tamoxifen in women at increased risk for breast cancer has produced encouraging results
To evaluate the use of low-dose tamoxifen, we proposed this clinical trial administering tamoxifen at a dose of 10 mg/day for 14 days in the neoadjuvant treatment of invasive breast carcinoma
The mean percentage of nuclei stained by Ki-67 (MIB-1) in Group B (10 mg of tamoxifen) before and after tamoxifen treatment was 24.69% and 10.43%, respectively
Summary
Chemoprophylaxis of breast carcinoma with tamoxifen in women at increased risk for breast cancer has produced encouraging results. Studies of primary chemoprevention with tamoxifen in usual doses have generated high expectations with a 50% reduction in the relative risk for invasive carcinoma in high-risk patients [1]. Some evidence indicates that tamoxifen dose can be lowered to reduce its side-effects and retain drug efficacy [1,2,3]. Tamoxifen and similar drugs act in a complex manner as estrogen antagonists in tumor tissue, and as estrogen agonists in other body tissues, including the bones, uterus and cardiovascular system. Alfa estrogen receptor (ERα), located on chromosome 6 is a protein comprising 595 aminoacids, with a molecular weight of 66 kDa. similar to other hormone receptors, the estrogen receptor is a modulated protein that can be divided into six different domains (A-B-C-DE-F) with specific functions [7,14]
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