Benign breast disease as a breast cancer risk in Japanese women

Gene-Environment Interaction between Arg72Pro SNP and Selected Environmental Exposures among Brazilian Women Diagnosed with Benign Breast Disease

Background:

Benign breast disease (BBD) is a factor strongly associated with breast cancer worldwide. Arg72Pro SNP association with breast cancer is controversial due to the suggestion that environmental factors are required to modulate such risk. There are no studies evaluating these environmental interactions of the aforementioned SNP within BBD.

Aim:

To determine the frequency of SNP Arg72Pro in a cohort of women diagnosed with BBD; and to investigate gene-environmental interactions with environmental factors.

Results:

The genotype frequency was 44.6% for Arg/Pro, 39.3% for Arg/Arg genotype, and 16.3% for Pro/Pro homozygote. Gene-environment interaction analysis shows that when Arg/Arg is considered as reference, there is an ORinteraction with Arg/Pro and fabric exposure (OR=1.90;95%CI:1.04,3.48), solvents (OR=2.21;95%CI:1.01,4.83) and chlorine, bleaches, disinfectants, and liquid wax exposure (OR=2.52;95%CI:1.07,5.91). Analysis with Pro/Pro genotype as the reference showed an interaction between alcohol consumption and recessive model (OR=1.58;95%CI:1.00,2.51). Gene-environmental interactions were observed too between exposure to hair dyes, straighteners or relaxers and Arg/Arg (OR=3.26;95%CI:1.21,8.82).

Conclusion:

The Arg/Pro genotype was the most frequent in the BBD cohort. When compared with the Arg/Arg genotype, the presence of Arg/Pro genotype and solvents, fabric and cleaning products exposure increased the risk of BBD. When compared with Pro/Pro genotype, there were interactions between recessive model with alcohol consumption and exposure to hair products on the risk of BBD.

Breast cancer risk associated with benign breast disease: systematic review and meta-analysis

Benign breast disease (BBD) is a broad category of diagnoses reported to convey a variable degree of increased risk of developing breast cancer. A meta-analysis of the existing literature was performed to quantify the risk estimate associated with BBD. Pubmed, Google Scholar, and EMBASE databases were searched in January 2011. English retrospective and prospective observational studies published from 1972 to 2010 evaluating BBD and the risk of breast cancer were included with data acquisition reported from 1930 to 2007. Eligibility was performed independently following a standardized protocol for full-text publication review by a single reviewer and reviewed by a second author. Of the 3,409 articles retrieved from the literature search, 32 studies met the selection criteria. Reported risk estimates, including relative risk, odds ratio, standardized incidence ratios, rate ratio, hazards ratio, and incidence rate ratio, were the primary outcomes extracted. The most commonly reported pathologies were decided prior to extraction and organized into the following categories for analysis of the extracted risk estimate: non-proliferative disease (NPD), proliferative disease without atypia, benign breast disease not otherwise specified (BBD), and atypical hyperplasia not otherwise specified (AHNOS). The mean age at benign breast biopsy was 46.1 years and the mean age of developing breast cancer was 55.9 years. The mean follow-up length was 12.8 years (range 3.3-20.6). The summary risk estimate of developing breast cancer for NPD was 1.17 (N = 8; 95% CI 0.94-1.47). Proliferative disease without atypia was associated with significantly increased risk of future breast cancer, summary relative risk 1.76 (N = 15; 95% CI 1.58-1.95). The summary risk estimate for AHNOS was 3.93 (N = 13; 95% CI 3.24-4.76). This meta-analysis demonstrates that proliferative benign breast disease with or without atypia is associated with a significant increase in risk of developing breast cancer. These data support management strategies for women with benign breast disease such as additional screening methods or chemoprevention.

Risk of breast cancer in Japanese women with benign breast disease

To investigate the risk of breast cancer development in women with benign breast disease (BBD), 387 screen-detected BBD women and 1,489 normal women, taken from participants in the breast cancer screening program during 1978-1986, were followed through 1991. While 2,811 person-years in the BBD group and 11,018 person-years in the normal group were accumulated, 5 women in the BBD group and 6 women in the normal group developed breast cancer. Using the Mantel-Haenszel method, relative risks (RR) were estimated for all women with BBD and women in some BBD types. Significantly elevated risk of breast cancer was observed in all women with BBD (RR = 3.26, 95% confidence interval (CI) 1.08-9.83). Women with proliferative BBD were at high risk of breast cancer (RR = 8.48, 95% CI 2.99-24.10), but no increased risk was observed for women with non-proliferative BBD (RR = 0.93, 95% CI 0.11-7.66). These results are consistent with those in high-risk countries for breast cancer. In the management of women with BBD, histopathological diagnosis of the breast lesion is essential and women with proliferative BBD should be followed up carefully.

Risk factors for benign breast disease according to histopathological type: comparisons with risk factors for breast cancer

We evaluated risk factors for benign breast disease by using a case-control study method. The series was taken from participants in breast cancer screening programs during 1978-1986 in Miyagi Prefecture, Japan. All benign breast lesions diagnosed during this period were reviewed and reclassified into proliferative and non-proliferative types based on the Dupont and Page classification. Data on 382 benign breast disease cases (130 proliferative-type cases and 252 non-proliferative-type cases) and 1,489 screening year-, age- and screening area-matched normal controls were used for analysis. Nulliparity or low parity and family history of breast cancer in mother or sisters were significantly associated with an increased risk of proliferative type. Premenopausal status was significantly associated with an increased risk of non-proliferative type. No significant association with history of lactation for the last child was observed in either type, but the risk of proliferative type increased with increasing duration of lactation (P=0.08). A comparison between the present findings and the risk factors for breast cancer indicated epidemiologic similarities between proliferative benign and malignant breast lesions in general. The associations of these two lesions with lactation patterns were, however, dissimilar.

Breast cancer: aetiological factors and associations (a possible protective role of phytoestrogens)

BACKGROUND

In spite of many known and suspected factors associated with the risk of breast cancer there has until recently been no explanation for its continuing increase in women of Western societies over recent decades or why there has not been an equivalent increase in women of most Asian and other less Westernized societies. It has long been suspected that a significant factor has been an increasing change of diet in Western societies from one predominantly vegetarian to one with a high content of meat and dairy products as well as 'refined' foods. Although diet has long been suspected there has otherwise been no real explanation as to the mechanism of the change in incidence of breast cancer.

METHODS

A comprehensive literature review has been made of aetiological factors and associations concerning breast cancer to determine whether any consistent trend can explain the rising incidence in Western societies.

RESULTS

There are a number of likely contributory factors but there is now accumulating evidence that the single most important difference is that people having a vegetarian diet have a high intake of legumes and other plant foods containing a variety of lignans and isoflavonoids. These appear to have an important role as nature's sex hormone modulators. These agents appear to be biologically active in a number of ways not yet completely understood but they do have both a weak oestrogenic effect and an anti-oestrogenic competitive effect, thus reducing the potential carcinogenic action of prolonged oestrogen activity. A probable additional benefit of such diets could be the role of dietary fibre.

CONCLUSIONS

A major problem of Western diets may not be the presence of meat or dairy products in the diet but the absence of desirable ingredients of vegetarian diets, namely dietary fibre and certain plant lignans and isoflavonoids. A modification of diet to include a greater proportion of fibre and soy or other leguminous plant food should be studied. Alternatively addition of more fibre and lignans and especially isoflavonoids to traditional Western diets would seem worthy of serious investigation. Such influences appear to have their greatest impact early in life and therefore could be especially important for girls and young women in Western societies.

Dietary Fat, Fatty Acids and Breast Cancer

Results from some, but not all, epidemiological studies, and experimental investigations using animal models indicate that the level of fat in the diet, and more importantly the nature of the constituent fatty acids, influence both breast cancer risk and the progression of the established disease. High-fat diets rich in polyunsaturated omega-6 fatty acids stimulate mammary carcinogenesis and tumor progression; the long-chain omega-3 fatty acids present at high concentration in some fish oils exert inhibitory effects. Prominent among the biochemical mechanisms involved is the regulation of eicosanoid biosynthesis from dietary linoleic acid; both prostaglandins resulting from cyclooxygenase activity, and the leukotrienes and hydroxy-fatty acids produced under the influence of the lipoxygenases are involved in mammary carcinogenesis, tumor cell growth and apoptosis, angiogenesis, invasion and metastasis. A shift towards the typical high-fat Western diet, rich in omega-6 and poor in omega-3 fatty acids, may be a major factor in the increasing breast cancer incidence and mortality rates in Japanese women. Moreover, the results of the preclinical studies, together with supporting epidemiological data, suggest that a nutritional intervention comprising dietary omega-3 fatty acid supplementation and, in populations consuming a high fat diet a reduction in total fat and omega-6 fatty acid intake, may have a place not only in breast caner prevention, but as an adjunct to the surgical treatment of the breast cancer patient.