Preventing breast cancer now by acting on what we already know

Air Pollution and Breast Cancer Incidence in the Multiethnic Cohort Study

PURPOSE

Recent studies suggested fine particulate matter (PM2.5) exposure increases the risk of breast cancer, but evidence among racially and ethnically diverse populations remains sparse.

MATERIALS AND METHODS

Among 58,358 California female participants of the Multiethnic Cohort (MEC) Study followed for an average of 19.3 years (1993-2018), we used Cox proportional hazards regression to examine associations of time-varying PM with invasive breast cancer risk (n = 3,524 cases; 70% African American and Latino females), adjusting for sociodemographics and lifestyle factors. Subgroup analyses were conducted for race and ethnicity, hormone receptor status, and breast cancer risk factors.

RESULTS

Satellite-based PM2.5 was associated with a statistically significant increased incidence of breast cancer (hazard ratio [HR] per 10 μg/m3, 1.28 [95% CI, 1.08 to 1.51]). We found no evidence of heterogeneity in associations by race and ethnicity and hormone receptor status. Family history of breast cancer showed evidence of heterogeneity in PM2.5-associations (Pheterogeneity = .046). In a meta-analysis of the MEC and 10 other prospective cohorts, breast cancer incidence increased in association with exposure to PM2.5 (HR per 10 μg/m3 increase, 1.05 [95% CI, 1.00 to 1.10]; P = .064).

CONCLUSION

Findings from this large multiethnic cohort with long-term air pollutant exposure and published prospective cohort studies support PM2.5 as a risk factor for breast cancer. As about half of breast cancer cannot be explained by established breast cancer risk factors and incidence is continuing to increase, particularly in low- and middle-income countries, our results highlight that breast cancer prevention should include not only individual-level behavior-centered approaches but also population-wide policies and regulations to curb PM2.5 exposure.

Reproductive Risk Factor Patterns in Caribbean Women With Breast Cancer Across 4 Generations

Importance

Breast cancer (BC) is commonly diagnosed among Caribbean women. Shifts in reproductive patterns modify the incidence of BC diagnosis and age at BC diagnosis in population-based studies; however, reproductive patterns in Caribbean women remain understudied.

Objective

To describe the temporal trends in reproductive patterns and age at BC diagnosis in Caribbean-born women.

Design, Setting, and Participants

A cross-sectional observational study-the Caribbean Women's Cancer Study-was conducted, with data on reproductive patterns known to affect BC risk collected in The Bahamas, Barbados, Cayman Islands, Dominica, Haiti, Jamaica, and Trinidad and Tobago. Participants were recruited prospectively. The sample included women born in Caribbean countries and diagnosed with invasive BC and/or ovarian cancer from June 1, 2010, to June 30, 2018, and was divided into 4 birth cohorts (born before 1950, 1950-1959, 1960-1969, and in or after 1970). Data were analyzed between August 1, 2023, and July 31, 2024.

Exposures

Receipt of a BC diagnosis and birth in a Caribbean country.

Main Outcomes and Measures

Change in reproductive patterns between birth cohorts, including age at BC diagnosis, family history of cancer, age at first pregnancy, number of pregnancies, number of full-term pregnancies, number of siblings, age at menarche and menopause, estrogen receptor status, and germline pathogenic/likely pathogenic variants.

Results

Of 1015 participants diagnosed with BC and ovarian cancer, 995 women (mean [SD] age, 46.6 [10.8] years; 605 [81.8%] Afro-Caribbean, 98 [13.2%] East Indian, 22 [3.0%] White, and 12 [1.6%] >1 race) received a diagnosis of invasive BC. Comparison from older to younger birth cohorts (presented in the order of born before 1950, 1950-1959, 1960-1969 and in or after 1970) showed an increased proportion of women experiencing menarche at age 12 years or younger (33.0% vs 47.3% vs 45.5% vs 57.9%; P < .001), women with no pregnancies (6.8% vs 6.8% vs 10.5% vs 22.8%; P < .001), and nulliparous women (8.6% vs 9.2% vs 13.9% vs 27.6%; P < .001). Younger age at BC diagnosis was observed in women experiencing menarche at age 12 years or younger (mean [SD], 45.0 [10.5] years) vs 15 years or older (mean [SD], 49.1 [11.2] years) and in nulliparous women (mean [SD], 42.1 [11.2] years) vs 3 or more full-term pregnancies (mean [SD], 49.9 [10.6] years; P < .001). For every year of first pregnancy delay, women had a 4% increased chance of being diagnosed with estrogen receptor-positive tumors (odds ratio, 1.04; 95% CI, 1.01-1.08; P = .02).

Conclusions and Relevance

In this cross-sectional study, between each 10-year birth cohort, women diagnosed with BC had a lower age at menarche, number of pregnancies, and number of full-term pregnancies. These findings suggest that interventions targeting other BC risk factors need to be implemented.

The Associations between Intakes of One-Carbon Metabolism-Related Vitamins and Breast Density among Young Women

BACKGROUND

Folate is the primary methyl donor and B vitamins are cofactors for one-carbon metabolism that maintain DNA integrity and epigenetic signatures implicated in carcinogenesis. Breast tissue is particularly susceptible to stimuli in early life. Only limited data are available on associations of one-carbon metabolism-related vitamin intake during youth and young adulthood with breast density, a strong risk factor for breast cancer.

METHODS

Over 18 years in the DISC and DISC06 Follow-up Study, diets of 182 young women were assessed by three 24-hour recalls on five occasions at ages 8 to 18 years and once at 25 to 29 years. Multivariable-adjusted linear mixed-effects regression was used to examine associations of intakes of one-carbon metabolism-related vitamins with MRI-measured percent dense breast volume (%DBV) and absolute dense breast volume (ADBV) at ages 25 to 29 years.

RESULTS

Folate intake in youth was inversely associated with %DBV (Ptrend = 0.006) and ADBV (Ptrend = 0.02). These inverse associations were observed with intake during post-, though not premenarche. In contrast, premenarche vitamin B2 intake was positively associated with ADBV (Ptrend < 0.001). Young adult folate and vitamin B6 intakes were inversely associated with %DBV (all Ptrend ≤ 0.04), whereas vitamins B6 and B12 were inversely associated with ADBV (all Ptrend ≤ 0.04).

CONCLUSIONS

Among these DISC participants intakes of one-carbon metabolism-related vitamins were associated with breast density. Larger prospective studies among diverse populations are needed to replicate these findings.

IMPACT

Our results suggest the importance of one-carbon metabolism-related vitamin intakes early in life with development of breast density and thereby potentially breast cancer risk later in life.

Reversion of breast epithelial polarity alterations caused by obesity

Molecular links between breast cancer risk factors and pro-oncogenic tissue alterations are poorly understood. The goal of this study was to characterize the impact of overweight and obesity on tissue markers of risk, using normal breast biopsies, a mouse model of diet-induced obesity, and cultured breast acini. Proliferation and alteration of epithelial polarity, both necessary for tumor initiation, were quantified by immunostaining. High BMI (>30) and elevated leptin were associated with compromised epithelial polarity whereas overweight was associated with a modest increase in proliferation in human and mice mammary glands. Human serum with unfavorable adipokine levels altered epithelial polarization of cultured acini, recapitulating the effect of leptin. Weight loss in mice led to metabolic improvements and restored epithelial polarity. In acini cultures, alteration of epithelial polarity was prevented by antioxidants and could be reverted by normalizing culture conditions. This study shows that obesity and/or dietary factors modulate tissue markers of risk. It provides a framework to set target values for metabolic improvements and to assess the efficacy of interventional studies aimed at reducing breast cancer risk.

Six Applications of Plant Based Diets for Health Promotion

The field of medicine, despite its prominent influence in society, has invested little to promote healthy lifestyle choices. The consequence of this is reflected in our ever-rising chronic disease statistics, most notably obesity and diabetes rates. This is especially regrettable considering overwhelming evidence confirms most non-communicable disease is preventable by modifying our diets. In light of this critical knowledge that optimizing our nutrition could save innumerable lives, one would naturally assume physicians would be readily practicing its promotion with their patients. Yet, that is far from true. By no fault of their own. Medical schools, entrusted with the responsibility of educating our future healthcare leaders, have managed to largely bypass the topic of nutrition, arguably the most powerful healthcare intervention known to mankind. In fact, on average, medical schools offer an anemic number of hours of nutrition education over 4 years. 1 What little is offered is focused on biochemistry and nutrient deficiencies, none of which prepares a physician in training for meaningful application in clinical care. This lapse in nutrition education continues throughout post-graduate training; in a recent survey of more than 600 cardiologists, 90% reported they had not received needed nutrition education during training. 2 Although we agree that not all physicians must be experts in nutrition, in the very least all should have knowledge of rudimentary and essential facts. We offer this commentary on six vital clinical topics, to increase awareness amongst physicians as to the importance of diet and its role in human health.

Cost-Effectiveness of Lifestyle-Related Interventions for the Primary Prevention of Breast Cancer: A Rapid Review

Background: In 2018, the global estimate of newly diagnosed breast cancer cases among women totaled 2.1 million. The economic and social burden that breast cancer places on societies has propelled research that analyzes the role of modifiable risk factors as the primary prevention methods. Healthy behavior changes, moderated alcohol intake, healthy body weight, and regular physical activity may decrease the risk of breast cancer among women. This review aimed to synthesize evidence on the cost-effectiveness of lifestyle-related interventions for the primary prevention of breast cancer in order to answer the question on whether implementing interventions focused on behavior changes are worth the value for money.

Methods: A rapid review was performed using search terms developed by the research team. The articles were retrieved from MEDLINE and the Tufts Medical Center Cost-Effectiveness Analysis Registry, with an additional web search in Google and Google Scholar. Comparisons were performed on the cost-effectiveness ratio per quality-adjusted life-year between the interventions using a league table, and the likelihood of cost-effective interventions for breast cancer primary prevention was analyzed.

Results: Six studies were selected. The median cost-effectiveness ratio (in 2018 USD) was $24,973, and 80% of the interventions had a ratio below the $50,000 threshold. The low-fat-diet program for postmenopausal women was cost-effective at a societal level, and the physical activity interventions, such as the Be Active Program in the UK, had the best cost saving results. A total of 11 of the 25 interventions ranked either as highly or very highly likely to be cost-effective for breast cancer primary preventions.

Conclusion: Although the review had some limitations due to using only a few studies, it showed evidence that diet-related and physical-activity-related interventions for the primary prevention of breast cancer were cost-effective. Many of the cost-effective interventions aimed to reduce the risk of non-communicable diseases alongside breast cancer.

A Pooled Analysis of Breastfeeding and Breast Cancer Risk by Hormone Receptor Status in Parous Hispanic Women

BACKGROUND

Data on breastfeeding and breast cancer risk are sparse and inconsistent for Hispanic women.

METHODS

Pooling data for nearly 6,000 parous Hispanic women from four population-based studies conducted between 1995 and 2007 in the United States and Mexico, we examined the association of breastfeeding with risk of breast cancer overall and subtypes defined by estrogen receptor (ER) and progesterone receptor (PR) status, and the joint effects of breastfeeding, parity, and age at first birth. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression.

RESULTS

Among parous Hispanic women, older age at first birth was associated with increased breast cancer risk, whereas parity was associated with reduced risk. These associations were found for hormone receptor positive (HR+) breast cancer only and limited to premenopausal women. Age at first birth and parity were not associated with risk of ER- and PR- breast cancer. Increasing duration of breastfeeding was associated with decreasing breast cancer risk (≥25 vs. 0 months: OR = 0.73; 95% CI = 0.60, 0.89; Ptrend = 0.03), with no heterogeneity by menopausal status or subtype. At each parity level, breastfeeding further reduced HR+ breast cancer risk. Additionally, breastfeeding attenuated the increase in risk of HR+ breast cancer associated with older age at first birth.

CONCLUSIONS

Our findings suggest that breastfeeding is associated with reduced risk of both HR+ and ER- and PR- breast cancer among Hispanic women, as reported for other populations, and may attenuate the increased risk in women with a first pregnancy at older ages.

Physician and Patient Barriers to Breast Cancer Preventive Therapy

The uptake of selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs) for the primary prevention of breast cancer is low, despite their proven efficacy in several randomized clinical trials. This review summarizes the latest data on physicians' and women's barriers to breast cancer preventive therapy. Physicians' challenges include: identifying suitable candidates for preventive therapy, inadequate training and confidence in risk assessment and counselling, insufficient knowledge of risk-reducing medications, and lack of time. High-risk women fear medication side effects, and they often weigh experiences of others more heavily than statistical probabilities to guide their decision-making. Despite decision aid interventions to help women make an informed decision, acceptance of preventive therapy will remain low until: risk/benefit profiles are more favorable, physicians are better educated and skilled in having these discussions, and suitable biomarkers to monitor drug efficacy and better clinical risk prediction models to assess true individual risk are available.