Synergistic Effect Between Full-Term Pregnancy/Breastfeeding And Familial Susceptibility On Breast Cancer Risk

Association between breastfeeding, mammographic density, and breast cancer risk: a review

BACKGROUND

Mammographic density has been associated with breast cancer risk, and is modulated by established breast cancer risk factors, such as reproductive and hormonal history, as well as lifestyle. Recent epidemiological and biological findings underscore the recognized benefits of breastfeeding in reducing breast cancer risk, especially for aggressive subtypes. Current research exploring the association among mammographic density, breastfeeding, and breast cancer is sparse.

MAIN FINDINGS

Changes occur in the breasts during pregnancy in preparation for lactation, characterized by the proliferation of mammary gland tissues and the development of mammary alveoli. During lactation, the alveoli fill with milk, and subsequent weaning triggers the involution and remodeling of these tissues. Breastfeeding influences the breast microenvironment, potentially altering mammographic density. When breastfeeding is not initiated after birth, or is abruptly discontinued shortly after, the breast tissue undergoes forced and abrupt involution. Conversely, when breastfeeding is sustained over an extended period and concludes gradually, the breast tissue undergoes slow remodeling process known as gradual involution. Breast tissue undergoing abrupt involution displays denser stroma, altered collagen composition, heightened inflammation and proliferation, along with increased expression of estrogen receptor α (ERα) and progesterone receptor. Furthermore, elevated levels of pregnancy-associated plasma protein-A (PAPP-A) surpass those of its inhibitors during abrupt involution, enhancing insulin-like growth factor (IGF) signaling and collagen deposition. Prolactin and small molecules in breast milk may also modulate DNA methylation levels. Drawing insights from contemporary epidemiological and molecular biology studies, our review sheds light on how breastfeeding impacts mammographic density and explores its role in influencing breast cancer.

CONCLUSION

This review highlights a clear protective link between breastfeeding and reduced breast cancer risk via changes in mammographic density. Future research should investigate the effects of breastfeeding on mammographic density and breast cancer risk among various ethnic groups and elucidate the molecular mechanisms underlying these associations. Such comprehensive research will enhance our understanding and facilitate the development of targeted breast cancer prevention and treatment strategies.

Breastfeeding and its Association with Breast Cancer: a Systematic Review of the Literature

Objective:Breast cancer is a global public health issue. The disease can be diagnosed in both older and younger women, with the latter facing several dilemmas. Breastfeeding is of general concern to the scientific community as well as its connection with the prevention of breast cancer is being sought. The purpose of this review is to search for studies investigating the relationship between breast cancer and breastfeeding. Material and methods: The articles included in the present paper were searched in PubMed and Scopus databases according to PRISMA guidelines for systematic reviews. This systematic review sought primary studies investigating the relationship between breastfeeding and breast cancer and that were published in English between 2017-2022. Results:Seventeen articles that investigated the relationship of breast cancer with lactation duration, women's age, family history and lifestyle were included in the present review. Conclusion:It was found that, in most studies, breastfeeding could be evaluated as a protective factor of the disease. From all studied articles, the need for the design of additional studies investigating the relationship between breastfeeding and breast cancer emerges.

Temporal Trends in the Incidence and Mortality of Major Reproductive-Related Cancers in Women in Guangzhou From 2010 to 2020: A Joinpoint and Age-Period-Cohort Study

Objective: To understand the temporal trends of cancer incidence and mortality in women in Guangzhou during the past 11 years and provide clues for future research. Methods: Data were obtained from the Guangzhou Cancer and Death Registry. Average annual percentage changes (AAPCs) in age-standardized incidence rates (ASIRs) and age-standardized mortality rates (ASMRs) were obtained by joinpoint regression. The age-period-cohort (APC) model was generated to quantify the effects of age, period, and cohort. Results: The ASIRs for cervical (AAPC = -4.3%) and ovarian (AAPC = -3.2%) cancers showed a downward trend during 2010-2020, and that for uterine cancer showed an upward trend. The ASMRs of breast (APC = 5.0%) and cervical (APC = 8.8%) cancers increased. The APC model highlights different age, period, and birth cohort effects depending on the cancer site. Conclusion: The ASIRs for cervical and ovarian cancers among women in Guangzhou showed a decreasing trend during the period. The APC model showed mortality for 4 cancers increased with age. Incidence and mortality decreased with increasing birth cohort. Annual reproductive cancer screening is recommended for women of appropriate age to reduce the disease burden.

Hereditary and breastfeeding factors are positively associated with the aetiology of mammary gland hyperplasia: a case-control study

BACKGROUND

Hyperplasia of mammary gland (HMG) has become a common disorder in women. A family history of breast cancer and female reproductive factors may work together to increase the risk of HMG. However, this specific relationship has not been fully characterized.

METHODS

A total of 1881 newly diagnosed HMG cases and 1900 controls were recruited from 2012 to 2017. Demographic characteristics including female reproductive factors and a family history of breast cancer were collected. A multi-analytic strategy combining unconditional logistic regression, multifactor dimensionality reduction (MDR) and crossover approaches were applied to systematically identify the interaction effect of family history of breast cancer and reproductive factors on HMG susceptibility.

RESULTS

In MDR analysis, high-order interactions among higher-level education, shorter breastfeeding duration and family history of breast cancer were identified (odds ratio [OR] 7.07 [95% confidence interval {CI} 6.08 to 8.22]). Similarly, in crossover analysis, HMG risk increased significantly for those with higher-level education (OR 36.39 [95% CI 11.47 to 115.45]), shorter duration of breastfeeding (OR 27.70 [95% CI 3.73 to 205.70]) and a family history of breast cancer.

CONCLUSION

Higher-level education, shorter breastfeeding duration and a family history of breast cancer may synergistically increase the risk of HMG.