A population-based case-control study was conducted in Sweden and Norway to analyse possible associations between breast cancer occurring before the age of 45 and several different characteristics of the women's reproductive life. A total of 422 (89.2%) of all eligible patients, and 527 (80.6%) of all eligible controls were interviewed. In univariate analyses, different characteristics of child-bearing (parity, age at first birth, years between last birth and diagnosis, duration of breast-feeding, and number of induced and spontaneous abortions), measures of the fertile or ovulating period (age at menarche, years between menarche and first pregnancy, and estimates of the menstruation span) and symptoms of anovulatory cycles or infertility were all seemingly unrelated to, or at most weakly associated with breast cancer. Adjustment for possible confounding factors in multivariate analyses resulted in largely unaltered risk estimates with odds ratios close to unity and without any significant trends when the exposure variables were studied in categorised or in continuous form. We conclude that reproductive factors did not explain the occurrence of breast cancer before the age of 45 in this population.
BACKGROUND: The risk of contralateral breast cancer is increased twofold to fivefold for breast cancer patients. A registry-based cohort study in Denmark suggested that radiation treatment of the first breast cancer might increase the risk for contralateral breast cancer among 10-year survivors. PURPOSE: Our goal was to assess the role of radiation in the development of contralateral breast cancer. METHODS: A nested case-control study was conducted in a cohort of 56,540 women in Denmark diagnosed with invasive breast cancer from 1943 through 1978. Case patients were 529 women who developed contralateral breast cancer 8 or more years after first diagnosis. Controls were women with breast cancer who did not develop contralateral breast cancer. One control was matched to each case patient on the basis of age, calendar year of initial breast cancer diagnosis, and survival time. Radiation dose to the contralateral breast was estimated for each patient on the basis of radiation measurements and abstracted treatment information. The anatomical position of each breast cancer was also abstracted from medical records. RESULTS: Radiotherapy had been administered to 82.4% of case patients and controls, and the mean radiation dose to the contralateral breast was estimated to be 2.51 Gy. Radiotherapy did not increase the overall risk of contralateral breast cancer (relative risk = 1.04; 95% confidence interval = 0.74-1.46), and there was no evidence that risk varied with radiation dose, time since exposure, or age at exposure. The second tumors in case patients were evenly distributed in the medial, lateral, and central portions of the breast, a finding that argues against a causal role of radiotherapy in tumorigenesis. CONCLUSIONS: The majority of women in our series were perimenopausal or postmenopausal (53% total versus 38% premenopausal and 9% of unknown status) and received radiotherapy at an age when the breast tissue appears least susceptible to the carcinogenic effects of radiation. Based on a dose of 2.51 Gy and estimates of radiation risk from other studies, a relative risk of only 1.18 would have been expected for a population of women exposed at an average age of 51 years. Thus, our data provide additional evidence that there is little if any risk of radiation-induced breast cancer associated with exposure of breast tissue to low-dose radiation (e.g., from mammographic x rays or adjuvant radiotherapy) in later life.
Age at first full-term pregnancy (FTP) has long been thought to be the major reproductive risk factor in breast cancer but a Norwegian study suggested that age at last FTP might be more important. In Norway "high parity" means 4 or more deliveries. Does this finding hold in an area with a much broader distribution of parity? Data from a case-control study done in 1980-82 in Fortaleza and Recife, two cities in Brazil's impoverished north-east, have been used to explore further the influence of age at last FTP. The cases were 509 women with histologically diagnosed breast cancer who were matched with hospital controls for age and area of residence. The analysis was based on case-control pairs interviewed by the same person. High breast cancer risk was associated with low parity; after adjustment for parity, breast cancer risk was related both to late age at first FTP (odds ratio [OR] 1.21 for each 5 year increase, p = 0.008) and to late age at last FTP (OR 1.24, p = 0.0007). However, multivariate analysis revealed that the effect of age at last FTP dominated that of age at first FTP: once age at last FTP was taken into account the effect of age at first FTP was no longer significant (OR 1.08, p = 0.38) while the association with parity became more striking. These results challenge the view that age at first FTP is the principal reproductive variable related to breast cancer risk. Moreover, they suggest that high parity is protective independent of ages at first and last FTP. Given recent worldwide reductions in fertility rates, breast cancer incidence may be expected to increase. Balancing that may be the willingness of some women to complete their families by, say, age 35 if they were to be told that this might reduce their risk of breast cancer.
Comment In: Lancet. 1993 Feb 20;341(8843):502-38094531
Comment In: Lancet. 1993 Jan 2;341(8836):24-58093271
Alcohol intake has consistently been associated with increased breast cancer incidence in epidemiological studies. However, the relation between alcohol and survival after breast cancer diagnosis is less clear.
We investigated whether alcohol intake was associated with survival among 3146 women diagnosed with invasive breast cancer in the Swedish Mammography Cohort. Alcohol consumption was estimated using a food frequency questionnaire. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (95% CIs).
From 1987 to 2008 there were 385 breast cancer-specific deaths and 860 total deaths. No significant association was observed between alcohol intake and breast cancer-specific survival. Women who consumed 10 g per day (corresponding to approximately 0.75 to 1 drinks) or more of alcohol had an adjusted HR (95% CI) of breast cancer-specific death of 1.36 (0.82-2.26;p(trend)=0.47) compared with non-drinkers. A significant inverse association was observed between alcohol and non-breast cancer deaths. Those who consumed 3.4-9.9 g per day of alcohol had a 33% lower risk of death compared with non-drinkers (95% CI 0.50-0.90;p(trend)=0.04).
Our findings suggest that alcohol intake up to approximately one small drink per day does not negatively impact breast cancer-specific survival and a half drink per day is associated with a decreased risk of mortality from other causes.
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With the help of mathematical methods of pattern recognition the analysis of complex cancer risk factors was conducted aiming at estimation the role of chronic radiation exposure in development of lung and breast cancer in dwellers of an industrial city exposed to irregular radioactive contamination as a result of an accident at PO "Mayak". It was shown, that chronic radiation exposure is an important factor, influenced the development of malignant neoplasms in city population.
Large childhood body size has been consistently shown to be associated with decreased breast cancer risk. However, it is important to consider the effects of a large childhood body size on other adult diseases. It is not clear if the associations between childhood body size and adult diseases will persist if they later attain healthy weight. The associations between body size at age 7 and 17 adverse outcomes in adulthood were examined using Cox models in a Swedish study of 65,057 women. Large body size at age 7, when compared to small body size, was associated with decreased risk for breast cancer (HR [95% CI]: 0.81 [0.70-0.93]) and increased risks for anorexia (2.13 [1.63-2.77]) and bulimia (1.91 [1.35-2.70]). Neither adjusting for adult BMI nor restricting the dataset to lean adults (BMI?
Breast cancer may be related to oxidative stress. Breast cancer patients have been reported to have lower antioxidant enzyme activity than healthy controls and the polymorphism GPX1 Pro198Leu has been associated with risk of lung and breast cancer. The purpose of the present nested case-control study was to determine whether GPX1 Pro198Leu and glutathione peroxidase (GPX) activity in prospectively collected blood samples are associated with breast cancer risk among postmenopausal women and whether GPX activity levels are associated with other known breast cancer risk factors. We matched 377 female breast cancer cases with 377 controls all nested within the prospective 'Diet, Cancer and Health' study of 57 000 Danes. Carriers of the variant T-allele of GPX1 Pro198Leu were at 1.43-fold higher risk of breast cancer compared with non-carriers (95% CI=1.07-1.92). Pre-diagnostic GPX activity tended to be lower in cases compared with controls. GPX activity was positively correlated with intake of alcohol (P
The hypothesis that birth weight is positively associated with adult risk of breast cancer implies that factors related to intrauterine growth may be important for the development of this malignancy. Using stored birth records from the two main hospitals in Trondheim and Bergen, Norway, we collected information on birth weight, birth length and placenta weight among 373 women who developed breast cancer. From the same archives, we selected as controls 1150 women of identical age as the cases without a history of breast cancer. Information on age at first birth and parity were collected from the Central Person Registry in Norway. Based on conditional logistic regression analysis, breast cancer risk was positively associated with birth weight and with birth length (P for trend=0.02). Birth weights in the highest quartile (3730 g or more) were associated with 40% higher risk (odds ratio, 1.4, 95% confidence interval, 1.1-1.9) of breast cancer compared to birth weights in the lowest quartile (less than 3090 g). For birth length, the odds ratio for women who were 51.5 cm or more (highest quartile) was 1.3 (95% confidence interval, 1.0-1.8) compared to being less than 50 cm (lowest quartile) at birth. Adjustment for age at first birth and parity did not change these estimates. Placenta weight was not associated with breast cancer risk. This study provides strong evidence that intrauterine factors may influence future risk of breast cancer. A common feature of such factors would be their ability to stimulate foetal growth and, simultaneously, to influence intrauterine development of the mammary gland.