Risk factors for breast cancer in Egyptian postmenopausal females in Alexandria

Background: Obesity is a modifiable risk factor for breast cancer in postmenopausal females. Aim: This study was conducted to investigate the association between obesity and breast cancer risk among Egyptian postmenopausal females in Alexandria. Subjects: This study included 100 Egyptian postmenopausal females, 50 of them were breast cancer patients with mean age (54.6 years± 9.6) and the other 50 were controls with mean age (53.9 years± 2.5). Methods: Standardized questionnaires concerning age, anthropometric, menstrual and reproductive information, family history of breast cancer in first degree relatives and history of hypertension were completed by the same researcher. Fasting blood samples were withdrawn from all participating females to separate sera in which total estradiol, insulin and glucose levels were measured. Results: Univariate analysis showed that age at presentation ≥ 60 years, delayed menopause > 50 years, family history of breast cancer in first degree relatives, oral contraceptive use, body mass index (BMI), waist circumference (WC) and serum levels of total estradiol were found to be significantly associated with higher risk of breast cancer in postmenopausal females. Multivariate logistic regression analysis showed that old age at presentation ≥ 60 years and late menopause >50 years were the strongest risk factors, while oral contraceptive use and increased WC >100 cm showed border line significance. Conclusion: Based on the results obtained from this study, we advice Egyptian postmenopausal females of Alexandria to control weight by decreasing dietary caloric intake, maintain physical activity and breast self-examination continuously in order to decrease the risk of breast carcinoma.


INTRODUCTION
Breast cancer is one of the most important problems of public health.(1)   Postmenopausal obesity was found to be a breast cancer risk factor.One of the consequences of obesity, insulin resistance decreases sensitivity of target tissues to circulating insulin resulting in hyperinsulinemia. (2)Hyperinsulinemia leads to reduction in the level of circulating sex hormone binding globulin (SHBG) coupled Bull High Inst Public Health Vol.41 No. 1 [2011]   with increased rate of proliferation of breast epithelial cells due to the increased amounts of free estradiol. ( Epidemiological analysis of breast cancer by hormone receptor status (HRS) shows distinct patterns for estrogen receptor positive (ER+) and estrogen receptor negative (ER−) cancers.Risk factor distribution differs among patients based on HRS with reproductive factors that increase a woman's lifetime exposure to endogenous estrogens resulting in ER+ cancer. (4)Other risk factors such as genetic risks, radiation and smoking give rise to ER− cancers. (5)The importance of studying risk factors for breast cancer according to HRS originates from the fact that presence of hormone receptor positive (HR+) breast cancer implies the best response to antiestrogen therapy, whereas hormone receptor negative (HR−) breast cancer implies poor response to anti-estrogen therapy.(6)   Studies that investigated the association between HRS and obesity have yielded conflicting results. (7-10) Dey et al. (11)   conducted a study in Tanta, Egypt and observed that the incidence of ER+ breast cancers was 2-4 times higher in Urban than in rural areas.Based on the results of this study, the present study was conducted to shed light on the situation in Alexandria as an urban region in Egypt regarding the association between obesity, reproductive and menstrual factors and the risk of breast cancer according to estrogen and progesterone receptor.

Sample size calculation:
Sample size was calculated using NCSS  Personal history of hypertension.
Waist Circumference (WC) was measured with a tape measure mid-way between the lower rib margin and the iliac crest.that all questions had valid codes, whereas skip checking was done to ensure that the correct set of questions was answered by each respondent.

3-Laboratory tests
ii. Recoding of variables: The quantitative variables were recoded using different cut off points defined by ROC analysis to include them in the analysis and enable the estimation of risk.
iii.Computation of new variables like body mass index.

B-Data analysis included:
1-Chi squared test for the categorical variables 2-Fisher exact test when the expected cell count was less than 5.
3-Calculation of the crude Odds Ratios to estimate the risk using the category with low breast cancer risk as a reference group.
4-Calculation of the mean±SD for the quantitative variables.
The results of the present study showed that age at first full-term pregnancy and parity were non-significantly associated, while oral contraceptive use was significantly associated with the risk of breast cancer in postmenopausal females.The proliferative effects of endogenous hormones support observations that exogenous exposure to hormones, primarily estrogen and progestin, is associated with breast cancer risk.Oral contraceptives provide a steady low level of hormones, which may be higher and more consistent than those occurring naturally. (19)It was found that estradiol is a primary stimulant for breast cells proliferation. ( The simultaneous presence of progesterone may increase the rate of proliferation. (21)This conclusion is based on the fact that breast mitotic activity peaks during the luteal phase of the menstrual cycle. (22)Our results were in agreement with those of Phipps et al. (23)   For the effect of abortion, high glucose levels and hypertension, our results were in agreement with Veronesi et al. (24) , Kabat et al. (25) and Peeters et al. (26) , respectively.
The results of the current study showed that increased BMI, WC, and serum level of total estradiol were significantly associated with breast cancer risk in postmenopusal females which were in agreement with the results found by McTiernan et al. (27) and Friedenreich. ( Friedenreich. (28)postulated that obesity may increase levels of circulating endogenous sex hormones which, in turn, increase breast cancer risk.Also, he suggested that with obesity, there are increased levels of fat tissue that can store toxins and can serve as a continuous source of carcinogens. (28) Although, Kabat et al (25) suggested that elevated serum insulin levels may be a risk factor for postmenopausal breast cancer, Phosphosaline, 0.025M EDTA, 0.08% sodium azide) was added, mixed by vortex and incubated for 20 minutes at 4°C.The reaction mixture was centrifuged at 4°C for 20 minutes at 5,000 rpm.The supernatant was completely decanted and the pellet was counted in a gamma counter for 1 minute (perkin Elmer, Finland).A calibration curve was constructed using known different concentrations of recombinant human insulin to determine the serum levels of human insulin.The assay sensitivity was 0.2 µU/ml and the specificity was 100%.Insulin resistance (IR) was quantified using the homeostatic model assessment (HOMA) according to the following equation (14) : HOMA-IR = (Glucose (mg/dl) × Insulin (µU/ml))/405 Serum total estradiol (E2) levels were determined using a ready-for-use RIA kit (SIEMENS, USA) according to the manufacturer's protocol.Briefly, 100 µl of serum and 1.0 ml of 125 I-radiolabeled E2 tracer were added to a polypropylene tube coated with E2 antibody.The mixture was mixed by vortex and incubated for 3 hours at room temperature.After incubation, reaction mixture was decanted thoroughly and the tube was counted for 1.0 minute in a gamma counter (perkin Elmer, Finland).A calibration curve was constructed using known different concentrations of human E2 to determine the serum levels of human E2.The assay sensitivity was 8 pg/ml.Data about ER and PR status were collected from patrents' pathology records after surgery.Statistical analysis: Data analysis was carried out using SPSS version 17, it included the following: A-Data processing Data processing had two major objectives namely clean data by performing a series of comprehensive checks and producing analytic results which involved the recoding of variables.i. Range checking and skip checking: Range checking was performed to ensure Bull High Inst Public Health Vol.41 No.1 [2011]

2 ,
for breast cancer was the dependent variable and family history of breast cancer in first-degree relatives, age at presentation≥ 60 yaers, BMI > 40 kg/m history of oral contraceptive use before menopause, age at menopause > 50 years, WC > 100 cm and serum total estradiol levels ≥ 20 pg/ml were independent variables, showed that the variables including age at presentation≥ 60 years, age at menopause > 50 years and serum total estradiol levels ≥ 20 pg/ml were the strongest risk factors for breast cancer in postmenopausal females.This means that postmenopausal females should continuously do breast self-examination for their breast monthly and do their best to prevent themselves from getting obese by maintaining physical exercise and decrease calories intake in their diets in order to protect themselves from getting breast carcinoma.Regarding the absence of the association between the studied factors and the risk for ER-positive and PR-positive breast cancer, our results are in agreement with many studies.Rosenberg et al. (29) found nonsignificant association of age at menopause and oral contraceptive use before menopause with the risk of developing ER-positive and PR-positive breast tumors in postmenopausal