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Background:Breast cancer is one of the most common cancers in women worldwide and one of its most desirable treatments is tamoxifen. The reported side effect associated with tamoxifen is endometrial thickness and increased risk of endometrial cancer. The aim of this study was to assess the influence of tamoxifen on the endometrial thickness in amenorrhea breast cancer patients treated with tamoxifen. Materials and Methods: This descriptive-analytic, cross-sectional study was conducted in Radiotherapy Departments of Mashhad University of Medical Sciences over a period of seven years.162 patients treated with tamoxifen whose bleeding cycle had been disrupted were selected and the relationship between tamoxifen usage and endometrial thickness was investigated in them. In addition, the relationship between abnormal vaginal bleeding and the ultra sonographic findings was assessed. Data analysis was done by using t-test and Chi-square test. Results: There was a significant relationship between tamoxifen usage and abnormal endometrial thickness while the greatest relationship was observed in the first year of treatment. The relationship between abnormal vaginal bleeding and abnormal endometrial sonographic findings was significant (P=0.001). The incidence of endometrial cancer in tamoxifen users was more than general population (0.61% vs. 0.1%). Conclusion: Considering the findings of this study, in the presence of abnormal sonographic and clinical observations indicating abnormal vaginal bleeding, pathological evaluation of the endometrial biopsy should be carried out for patients who use tamoxifen.

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Background and Aim: Tamoxifen is a group of drugs of selective estrogen receptor modulators, and is one of the drugs effective in the prevention and treatment of some cancers (such as breast cancer). In this study, the interaction of tamoxifen with DNA is investigated experimentally. Also, the electronic structure (at atomic scale) of the molecular system of tamoxifen was theoretically investigated, using atom in molecule (AIM) theory.
Methods & Materials: First, in the experimental section of this study, the interaction of Tamoxifen with DNA were investigated by UV-ViS technique and hydrodynamic method (Viscometry). In addition, the analysis of the experimental results shows the obvious effect of concentration on the mechanism of how the tamoxifen molecule binds to DNA. Then, in the theoretical part of this research, using computational biophysical chemistry methods, some properties of tamoxifen molecular system, such as electronic Density of States (DOS), boundary orbital’s energy (HOMO/LUMO), Electrostatic Potential Energy (EPS) and electronic contour maps of the electron density and its Laplacian, will be calculated.
Ethical Considerations: This article is a meta-analysis with animal sample.
Results: Result of the UV-ViS spectroscopy technique and viscometry indicated hyperchromism and hypochromism effect. In addition, the result were depend on the concentration of the drug and affected the kind of binding of Tamoxifen to DNA. the analysis of computational studies on the drug tamoxifen suggests that the mechanism of the local charge/energy distribution in the molecular system of tamoxifen plays an important role in how this drug binds to DNA.
Conclusion: Based on the experimental results of UV-ViS technique and viscometry, as well as the electronic/vibrational properties of the tamoxifen molecular system, it was defined that the Tamoxifen interacts significantly with all the binding sites of DNA.