Obesity has been linked to an increased risk of developing a number of malignancies, including postmenopausal breast cancer. One of the established risk factors for breast cancer development in post-menopausal women is obesity which has further been linked to breast cancer recurrence and poorer survival in pre- and post-menopausal breast cancer.

The biological mechanisms underlying the association between obesity and breast cancer could involve interacting mediators of hormones, adipocytokines, and inflammatory cytokines which link to cell survival or apoptosis, migration and proliferation. Higher level of oestradiol produced in postmenopausal women through aromatization of androgens in the adipose tissues and higher level of insulin, a condition common in obese women, are linked to poorer prognosis in breast cancer. A possible interaction between leptin, insulin and obesity-related markers of inflammation have also been linked to breast cancer outcomes. Non-biological mechanisms could include chemotherapy under-dosing in obese women, suboptimal treatment, and obesity-related complications.

The impact of body mass index on treatment outcome in patients receiving endocrine therapy, there have been consistent results indicating that the efficacy of aromatase inhibitors vary with body mass index; however, the efficacy of tamoxifen is not body mass index-dependent. In the Arimidex, Tamoxifen, Alone or in Combination trial, which compared the efficacy of anastrozole against tamoxifen as an adjuvant treatment for hormone receptor-positive post-menopausal breast cancer patients, anastrozole, a non-steroidal aromatase inhibitor, was significantly less effective in post-menopausal breast cancer patients with a high body mass index, whereas an equal efficacy of tamoxifen was shown across all body mass index levels.

Observational study. Retrospective analysis of data that will be collected from breast cancer patients medical records as body mass index and their response to treatment, progression free survival and overall survival.

Inclusion Criteria:

• Medical records of female Patients with breast cancer at clinical oncology and nuclear medicine department, Assiut University Hospital between (1st Jan 2012 and 31st Dec 2016), their recorded body mass index and their follow up will be included in the study.

Exclusion Criteria:

• Patients' medical records that had no documented weight and height.
• Patients' medical records that had no documented follow up.

Patients with breast cancer that was admitted at clinical oncology and nuclear medicine department, Assiut University Hospital, Egypt