Association of Endogenous Pregnenolone, Progesterone, and Related Metabolites with Risk of Endometrial and Ovarian Cancers in Postmenopausal Women: The BFIT Cohort

BACKGROUND

Postmenopausal pregnenolone and/or progesterone levels in relation to endometrial and ovarian cancer risks have been infrequently evaluated. To address this, we utilized a sensitive and reliable assay to quantify prediagnostic levels of seven markers related to endogenous hormone metabolism.

METHODS

Hormones were quantified in baseline serum collected from postmenopausal women in a cohort study nested within the Breast and Bone Follow-up to the Fracture Intervention Trial (B∼FIT). Women using exogenous hormones at baseline (1992-1993) were excluded. Incident endometrial (n = 65) and ovarian (n = 67) cancers were diagnosed during 12 follow-up years and compared with a subcohort of 345 women (no hysterectomy) and 413 women (no oophorectomy), respectively. Cox models with robust variance were used to estimate cancer risk.

RESULTS

Circulating progesterone levels were not associated with endometrial [tertile (T)3 vs. T1 HR (95% confidence interval): 1.87 (0.85-4.11); P _trend = 0.17] or ovarian cancer risk [1.16 (0.58-2.33); 0.73]. Increasing levels of the progesterone-to-estradiol ratio were inversely associated with endometrial cancer risk [T3 vs. T1: 0.29 (0.09-0.95); 0.03]. Increasing levels of 17-hydroxypregnenolone were inversely associated with endometrial cancer risk [0.40 (0.18-0.91); 0.03] and positively associated with ovarian cancer risk [3.11 (1.39-6.93); 0.01].

CONCLUSIONS

Using sensitive and reliable assays, this study provides novel data that endogenous progesterone levels are not strongly associated with incident endometrial or ovarian cancer risks. 17-hydroxypregnenolone was positively associated with ovarian cancer and inversely associated with endometrial cancer.

IMPACT

While our results require replication in large studies, they provide further support of the hormonal etiology of endometrial and ovarian cancers.

Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies

BACKGROUND

Epidemiologic studies examining the relations between dairy product and calcium intakes and breast cancer have been inconclusive, especially for tumor subtypes.

OBJECTIVE

To evaluate the associations between intakes of specific dairy products and calcium and risk of breast cancer overall and for subtypes defined by estrogen receptor (ER) status.

METHOD

We pooled the individual-level data of over 1 million women who were followed for a maximum of 8-20 years across studies. Associations were evaluated for dairy product and calcium intakes and risk of incident invasive breast cancer overall (n = 37,861 cases) and by subtypes defined by ER status. Study-specific multivariable hazard ratios (HRs) were estimated and then combined using random-effects models.

RESULTS

Overall, no clear association was observed between the consumption of specific dairy foods, dietary (from foods only) calcium, and total (from foods and supplements) calcium, and risk of overall breast cancer. Although each dairy product showed a null or very weak inverse association with risk of overall breast cancer (P, test for trend >0.05 for all), differences by ER status were suggested for yogurt and cottage/ricotta cheese with associations observed for ER-negative tumors only (pooled HR = 0.90, 95% CI: 0.83, 0.98 comparing ≥60 g/d with <1 g/d of yogurt and 0.85, 95% CI: 0.76, 0.95 comparing ≥25 g/d with <1 g/d of cottage/ricotta cheese). Dietary calcium intake was only weakly associated with breast cancer risk (pooled HR = 0.98, 95% CI: 0.97, 0.99 per 350 mg/d).

CONCLUSION

Our study shows that adult dairy or calcium consumption is unlikely to associate with a higher risk of breast cancer and that higher yogurt and cottage/ricotta cheese intakes were inversely associated with the risk of ER-negative breast cancer, a less hormonally dependent subtype with poor prognosis. Future studies on fermented dairy products, earlier life exposures, ER-negative breast cancer, and different racial/ethnic populations may further elucidate the relation.

Pregnancy outcomes and risk of endometrial cancer: A pooled analysis of individual participant data in the Epidemiology of Endometrial Cancer Consortium

A full-term pregnancy is associated with reduced endometrial cancer risk; however, whether the effect of additional pregnancies is independent of age at last pregnancy is unknown. The associations between other pregnancy-related factors and endometrial cancer risk are less clear. We pooled individual participant data from 11 cohort and 19 case-control studies participating in the Epidemiology of Endometrial Cancer Consortium (E2C2) including 16 986 women with endometrial cancer and 39 538 control women. We used one- and two-stage meta-analytic approaches to estimate pooled odds ratios (ORs) for the association between exposures and endometrial cancer risk. Ever having a full-term pregnancy was associated with a 41% reduction in risk of endometrial cancer compared to never having a full-term pregnancy (OR = 0.59, 95% confidence interval [CI] 0.56-0.63). The risk reduction appeared the greatest for the first full-term pregnancy (OR = 0.78, 95% CI 0.72-0.84), with a further ~15% reduction per pregnancy up to eight pregnancies (OR = 0.20, 95% CI 0.14-0.28) that was independent of age at last full-term pregnancy. Incomplete pregnancy was also associated with decreased endometrial cancer risk (7%-9% reduction per pregnancy). Twin births appeared to have the same effect as singleton pregnancies. Our pooled analysis shows that, while the magnitude of the risk reduction is greater for a full-term pregnancy than an incomplete pregnancy, each additional pregnancy is associated with further reduction in endometrial cancer risk, independent of age at last full-term pregnancy. These results suggest that the very high progesterone level in the last trimester of pregnancy is not the sole explanation for the protective effect of pregnancy.

Risk factors for contralateral breast cancer in postmenopausal breast cancer survivors in the NIH-AARP Diet and Health Study

PURPOSE

The role of established breast cancer risk factors and clinical characteristics of the first breast cancer in the development of contralateral breast cancer (CBC) among postmenopausal women is unclear.

METHODS

We identified 10,934 postmenopausal women diagnosed with a first primary breast cancer between 1995 and 2011 in the NIH-AARP Diet and Health Study. CBC was defined as a second primary breast cancer diagnosed in the contralateral breast ≥ 3 months after the first breast cancer. Exposures included pre-diagnosis risk factors (lifestyle, reproductive, family history) and clinical characteristics of the first breast cancer. We used multivariable Cox proportional hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Over a median follow-up of 6.8 years, 436 women developed CBC. We observed an increasing trend in CBC risk by age (p-trend = 0.002) and decreasing trend by year of diagnosis (p-trend = 0.001) of the first breast cancer. Additional risk factor associations were most pronounced for endocrine therapy (HR 0.68, 95% CI 0.53-0.87) and family history of breast cancer (HR 1.38, 95% CI 1.06-1.80, restricted to invasive first breast cancer). No associations were found for lifestyle (body mass index, physical activity, smoking, alcohol) or reproductive factors (age at menarche, parity, age at first birth, age at menopause).

CONCLUSIONS

This study suggests that clinical characteristics of the first breast cancer and family history of breast cancer, but not pre-diagnosis lifestyle and reproductive factors, are strongly associated with CBC risk among postmenopausal women. Future studies are needed to understand how these factors contribute to CBC etiology and to identify further opportunities for prevention.

Body Mass Index and Risk of Second Cancer Among Women With Breast Cancer

BACKGROUND

Breast cancer survivors are at increased risk for developing second primary cancers compared with the general population. Little is known about whether body mass index (BMI) increases this risk. We examined the association between BMI and second cancers among women with incident invasive breast cancer.

METHODS

This retrospective cohort included 6481 patients from Kaiser Permanente Colorado and Washington of whom 822 (12.7%) developed a second cancer (mean follow-up was 88.0 months). BMI at the first cancer was extracted from the medical record. Outcomes included: 1) all second cancers, 2) obesity-related second cancers, 3) any second breast cancer, and 4) estrogen receptor-positive second breast cancers. Multivariable Poisson regression models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for second cancers associated with BMI adjusted for site, diagnosis year, treatment, demographic, and tumor characteristics.

RESULTS

The mean age at initial breast cancer diagnosis was 61.2 (SD = 11.8) years. Most cases were overweight (33.4%) or obese (33.8%) and diagnosed at stage I (62.0%). In multivariable models, for every 5 kg/m2 increase in BMI, the risk of any second cancer diagnosis increased by 7% (RR = 1.07, 95% CI = 1.01 to 1.14); 13% (RR = 1.13, 95% CI = 1.05 to 1.21) for obesity-related cancers, 11% (RR = 1.11, 95% CI = 1.02 to 1.21) for a second breast cancer, and 15% (RR = 1.15, 95% CI = 1.04 to 1.27) for a second estrogen receptor-positive breast cancer.

CONCLUSIONS

We observed a statistically significant increased risk of second cancers associated with increasing BMI. These findings have important public health implications given the prevalence of overweight and obesity in breast cancer survivors and underscore the need for effective prevention strategies.

Risk factors for breast cancer development by tumor characteristics among women with benign breast disease

Background

Among women diagnosed with invasive breast cancer, 30% have a prior diagnosis of benign breast disease (BBD). Thus, it is important to identify factors among BBD patients that elevate invasive cancer risk. In the general population, risk factors differ in their associations by clinical pathologic features; however, whether women with BBD show etiologic heterogeneity in the types of breast cancers they develop remains unknown.

Methods

Using a nested case-control study of BBD and breast cancer risk conducted in a community healthcare plan (Kaiser Permanente Northwest), we assessed relationships of histologic features in BBD biopsies and patient characteristics with subsequent breast cancer risk and tested for heterogeneity of associations by estrogen receptor (ER) status, tumor grade, and size. The study included 514 invasive breast cancer cases (median follow-up of 9 years post-BBD diagnosis) and 514 matched controls, diagnosed with proliferative or non-proliferative BBD between 1971 and 2006, with follow-up through mid-2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were obtained using multivariable polytomous logistic regression models.

Results

Breast cancers were predominantly ER-positive (86%), well or moderately differentiated (73%), small (74% < 20 mm), and stage I/II (91%). Compared to patients with non-proliferative BBD, proliferative BBD with atypia conferred increased risk for ER-positive cancer (OR = 5.48, 95% CI = 2.14–14.01) with only one ER-negative case, P-heterogeneity = 0.45. The presence of columnar cell lesions (CCLs) at BBD diagnosis was associated with a 1.5-fold increase in the risk of both ER-positive and ER-negative tumors, with a 2-fold increase (95% CI = 1.21–3.58) observed among postmenopausal women (56%), independent of proliferative BBD status with and without atypia. We did not identify statistically significant differences in risk factor associations by tumor grade or size.

Conclusion

Most tumors that developed after a BBD diagnosis in this cohort were highly treatable low-stage ER-positive tumors. CCL in BBD biopsies may be associated with moderately increased risk, independent of BBD histology, and irrespective of ER status.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01410-1.

Risk of contralateral breast cancer according to first breast cancer characteristics among women in the USA, 1992-2016

Background

Estimates of contralateral breast cancer (CBC) risk in the modern treatment era by year of diagnosis and characteristics of the first breast cancer are needed to assess the impact of recent advances in breast cancer treatment and inform clinical decision making.

Methods

We examined CBC risk among 419,818 women (age 30–84 years) who were diagnosed with a first unilateral invasive breast cancer and survived ≥ 1 year in the US Surveillance, Epidemiology, and End Results program cancer registries from 1992 to 2015 (follow-up through 2016). CBC was defined as a second invasive breast cancer in the contralateral breast ≥ 12 months after the first breast cancer. We estimated standardized incidence ratios (SIRs) of CBC by year of diagnosis, age at diagnosis, and tumor characteristics for the first breast cancer. Cumulative incidence of CBC was calculated for women diagnosed with a first breast cancer in the recent treatment era (2004–2015, follow-up through 2016).

Results

Over a median follow-up of 8 years (range 1–25 years), 12,986 breast cancer patients developed CBC. Overall, breast cancer patients had approximately twice the risk of developing cancer in the contralateral breast when compared to that expected in the general population (SIR = 2.21, 95% CI = 2.17–2.25). SIRs for CBC declined by year of first diagnosis, irrespective of age at diagnosis and estrogen receptor (ER) status (p-trends < 0.001), but the strongest decline was after an ER-positive tumor. The 5-year cumulative incidence of CBC ranged from 1.01% (95% CI = 0.90–1.14%) in younger women (age < 50 years) with a first ER-positive tumor to 1.89% (95% CI = 1.61–2.21%) in younger women with a first ER-negative tumor.

Conclusion

Declines in CBC risk are consistent with continued advances in breast cancer treatment. The updated estimates of cumulative incidence inform breast cancer patients and clinicians on the risk of CBC and may help guide treatment decisions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01400-3.

Relation of Quantitative Histologic and Radiologic Breast Tissue Composition Metrics With Invasive Breast Cancer Risk

Background

Benign breast disease (BBD) is a strong breast cancer risk factor, but identifying patients that might develop invasive breast cancer remains a challenge.

Methods

By applying machine-learning to digitized hematoxylin and eosin-stained biopsies and computer-assisted thresholding to mammograms obtained circa BBD diagnosis, we generated quantitative tissue composition metrics and determined their association with future invasive breast cancer diagnosis. Archival breast biopsies and mammograms were obtained for women (18-86 years of age) in a case-control study, nested within a cohort of 15 395 BBD patients from Kaiser Permanente Northwest (1970-2012), followed through mid-2015. Patients who developed incident invasive breast cancer (ie, cases; n = 514) and those who did not (ie, controls; n = 514) were matched on BBD diagnosis age and plan membership duration. All statistical tests were 2-sided.

Results

Increasing epithelial area on the BBD biopsy was associated with increasing breast cancer risk (odds ratio [OR]_{Q4 vs Q1} = 1.85, 95% confidence interval [CI] = 1.13 to 3.04; P _trend = .02). Conversely, increasing stroma was associated with decreased risk in nonproliferative, but not proliferative, BBD (P _{heterogeneity} = .002). Increasing epithelium-to-stroma proportion (OR_{Q4 vs Q1} = 2.06, 95% CI =1.28 to 3.33; P _trend = .002) and percent mammographic density (MBD) (OR_{Q4 vs Q1} = 2.20, 95% CI = 1.20 to 4.03; P _trend = .01) were independently and strongly predictive of increased breast cancer risk. In combination, women with high epithelium-to-stroma proportion and high MBD had substantially higher risk than those with low epithelium-to-stroma proportion and low MBD (OR = 2.27, 95% CI = 1.27 to 4.06; P _trend = .005), particularly among women with nonproliferative (P _trend = .01) vs proliferative (P _trend = .33) BBD.

Conclusion

Among BBD patients, increasing epithelium-to-stroma proportion on BBD biopsies and percent MBD at BBD diagnosis were independently and jointly associated with increasing breast cancer risk. These findings were particularly striking for women with nonproliferative disease (comprising approximately 70% of all BBD patients), for whom relevant predictive biomarkers are lacking.

Breast Cancer Incidence Trends by Estrogen Receptor Status Among Asian American Ethnic Groups, 1990-2014

Background

Westernization and etiologic heterogeneity may play a role in the rising breast cancer incidence in Asian American (AA) women. We report breast cancer incidence in Asian-origin populations.

Methods

Using a specialized Surveillance, Epidemiology, and End Results-9 Plus API Database (1990-2014), we analyzed breast cancer incidence overall, by estrogen receptor (ER) status, and age group among non-Hispanic white (NHW) and AA women. We used age-period-cohort models to assess time trends and quantify heterogeneity by ER status, race and ethnicity, and age.

Results

Overall, breast cancer incidence increased for most AA ethnicities (Filipina: estimated annual percentage change [EAPC] = 0.96%/year, 95% confidence interval [CI] = 0.61% to 1.32%; South Asian: EAPC = 1.68%/year, 95% CI = 0.24% to 3.13%; Chinese: EAPC = 0.65%/year, 95% CI = 0.03% to 1.27%; Korean: EAPC = 2.55%/year, 95% CI = 0.13% to 5.02%; and Vietnamese women: EAPC = 0.88%/year, 95% CI = 0.37% to 1.38%); rates did not change for NHW (EAPC = -0.2%/year, 95% CI = -0.73% to 0.33%) or Japanese women (EAPC = 0.22%/year, 95% CI = -1.26% to 1.72%). For most AA ethnicities, ER-positive rates statistically significantly increased, whereas ER-negative rates statistically significantly decreased. Among older women, ER-positive rates were stable for NHW and Japanese women. ER-negative rates decreased fastest in NHW and Japanese women among both age groups.

Conclusions

Increasing ER-positive incidence is driving an increase overall for most AA women despite declining ER-negative incidence. The similar trends in NHW and Japanese women (vs other AA ethnic groups) highlight the need to better understand the influences of westernization and other etiologic factors on breast cancer incidence patterns in AA women. Heterogeneous trends among AA ethnicities underscore the importance of disaggregating AA data and studying how breast cancer differentially affects the growing populations of diverse AA ethnic groups.

The Association Between Periodontal Disease and Breast Cancer in a Prospective Cohort Study

Periodontal disease may be associated with increased breast cancer risk, but studies have not considered invasive breast cancer and ductal carcinoma in situ (DCIS) separately in the same population. We assessed the relationship between periodontal disease and breast cancer in a large prospective cohort study. The Sister Study followed women without prior breast cancer ages 35 to 74 years from 2003 to 2017 (N = 49,968). Baseline periodontal disease was self-reported, and incident breast cancer was ascertained over a mean follow-up of 9.3 years. We estimated hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards regression, adjusting for multiple potential confounders, including smoking status. Heterogeneity in risk for invasive breast cancer versus DCIS was also estimated. About 22% of participants reported a history of periodontal disease at baseline. A total of 3,339 incident breast cancers (2,607 invasive breast cancer, 732 DCIS) were identified. There was no clear association between periodontal disease and overall breast cancer risk (HR = 1.02; 95% CI, 0.94-1.11). However, we observed a nonstatistically significant suggestive increased risk of invasive breast cancer (HR = 1.07; 95% CI, 0.97-1.17) and decreased risk of DCIS (HR = 0.86; 95% CI, 0.72-1.04) associated with periodontal disease, with evidence for heterogeneity in the risk associations (relative HR for invasive breast cancer versus DCIS = 1.24; 95% CI, 1.01-1.52). A case-only analysis for etiologic heterogeneity confirmed this difference. We observed no clear association between periodontal disease and overall breast cancer risk. The heterogeneity in risk associations for invasive breast cancer versus DCIS warrants further exploration.

Use of postmenopausal hormone therapies and risk of histology- and hormone receptor-defined breast cancer: results from a 15-year prospective analysis of NIH-AARP cohort

Background

Menopausal hormone therapy (MHT) increases breast cancer (BC) risk, but cohort studies largely consider use only at enrollment. Evidence is limited on how changes in MHT use alter the magnitude of risk, and whether risk varies between invasive and in situ cancer, by histology or by hormone receptor status.

Methods

We investigated the roles of estrogen-alone therapy (ET) and estrogen plus progestin therapy (EPT) on BC risk overall, by histology and estrogen receptor (ER) and progesterone receptor (PR) status, and on incidence of in situ disease, in the NIH-AARP cohort. Participants included 118,760 postmenopausal women (50–71 years), of whom 63.5% (n = 75,398) provided MHT use information at baseline in 1996 and in a follow-up survey in 2004, subsequent to the dissemination in 2002 of the Women’s Health Initiative trial safety concerns regarding EPT. ET analyses included 50,476 women with hysterectomy (31,439 with follow-up data); EPT analyses included 68,284 women with intact uteri (43,959 with follow-up data). Adjusted hazard ratios (HRs) were estimated using Cox proportional hazards models using age as the time metric with follow-up through 2011.

Results

Eight thousand three hundred thirty-three incident BC cases were accrued, 2479 in women with follow-up data. BC risk was not elevated in current ET users at baseline (HR = 1.05, 95% confidence interval [CI] CI = 0.95–1.16) but was higher in women continuing use through 2004 (HR = 1.35, 95% CI = 1.04–1.75). Ever EPT use at baseline was associated with elevated BC risk overall (HR = 1.54 (1.44–1.64), with a doubling in risk for women with 10 or more years of use, for in situ disease, and across subtypes defined by histology and ER/PR status (all p < 0.004). Risk persisted in women who continued EPT through 2004 (HR = 1.80, 95% CI = 1.39–2.32). In contrast, no association was seen in women who discontinued EPT before 2004 (HR = 1.14, 95% CI = 0.99–1.30).

Conclusions

ET use was not associated with BC risk in this cohort, although excess risk was suggested in women who continued use through 2004. EPT use was linked to elevated in situ and invasive BC risk, and elevated risk across invasive BC histologic and hormone receptor-defined subtypes, with the highest risk for women who continued use through the 2004 follow-up survey.

Supplementary information

The online version contains supplementary material available at 10.1186/s13058-020-01365-9.

Outdoor air pollution and terminal duct lobular involution of the normal breast

Background

Exposure to certain outdoor air pollutants may be associated with a higher risk of breast cancer, though potential underlying mechanisms are poorly understood. We examined whether outdoor air pollution was associated with involution of terminal duct lobular units (TDLUs), the histologic site where most cancers arise and an intermediate marker of breast cancer risk.

Methods

Pathologist-enumerated TDLUs were assessed in H&E (hematoxylin and eosin)-stained breast tissue sections from 1904 US women ages 18–75 who donated to the Susan G. Komen Tissue Bank (2009–2012). The 2009 annual fine particulate matter < 2.5 μm in diameter (PM_2.5) total mass (μg/m³) at each woman’s residential address was estimated from the Environmental Protection Agency’s Downscaler Model combining Community Multiscale Air Quality (CMAQ) System modeling with air quality monitoring data. We secondarily considered CMAQ-modeled components of PM_2.5 and gaseous pollutants. We used K-means clustering to identify groups of individuals with similar levels of PM_2.5 components, selecting groups via cluster stability analysis. Relative rates (RRs) and 95% confidence intervals (95% CIs) for the association between air pollutants and TDLU counts were estimated from a zero-inflated negative binomial regression model adjusted for potential confounders.

Results

PM_2.5 total mass was associated with higher TDLU counts among all women (interquartile range (IQR) increase, RR = 1.06; 95% CI: 1.01–1.11). This association was evident among both premenopausal and postmenopausal women (premenopausal RR = 1.05, 95% CI: 1.00–1.11; postmenopausal RR = 1.11, 95% CI: 1.00–1.23). We identified 3 groups corresponding to clusters that varied geographically and roughly represented high, medium, and low levels of PM_2.5 components relative to population mean levels. Compared to the cluster with low levels, the clusters with both high (RR = 1.74; 95% CI: 1.08–2.80) and medium (RR = 1.82; 95% CI: 1.13–2.93) levels were associated with higher TDLU counts; although not significantly different, the magnitude of the associations was stronger among postmenopausal women.

Conclusions

Higher PM_2.5 levels were associated with reduced TDLU involution as measured by TDLU counts. Air pollution exposure may influence the histologic characteristics of normal tissue which could in turn affect breast cancer risk.

Polygenic risk score for the prediction of breast cancer is related to lesser terminal duct lobular unit involution of the breast

Terminal duct lobular units (TDLUs) are the predominant anatomical structures where breast cancers originate. Having lesser degrees of age-related TDLU involution, measured as higher TDLUs counts or more epithelial TDLU substructures (acini), is related to increased breast cancer risk among women with benign breast disease (BBD). We evaluated whether a recently developed polygenic risk score (PRS) based on 313-common variants for breast cancer prediction is related to TDLU involution in the background, normal breast tissue, as this could provide mechanistic clues on the genetic predisposition to breast cancer. Among 1398 women without breast cancer, higher values of the PRS were significantly associated with higher TDLU counts (P = 0.004), but not with acini counts (P = 0.808), in histologically normal tissue samples from donors and diagnostic BBD biopsies. Mediation analysis indicated that TDLU counts may explain a modest proportion (≤10%) of the association of the 313-variant PRS with breast cancer risk. These findings suggest that TDLU involution might be an intermediate step in the association between common genetic variation and breast cancer risk.

Abstract NG15: Investigation of relationships between breast cancer risk factors and bilateral mammographic breast density asymmetry among women undergoing diagnostic image-guided breast biopsies

Introduction: The etiology of breast cancer remains an area of ongoing investigation. Improving our understanding of factors associated with breast cancer development will strengthen the utility of risk prediction strategies and improve risk stratification. Mammographic breast density remains one of the most influential breast cancer risk factors, with 4 to 6 fold elevated risk observed among women with the highest compared to the lowest levels. These associations have consistently been observed irrespective of the method (visual or automated), used to quantify breast density, showing the robustness of the associations. An understudied breast cancer risk factor is the bilateral asymmetry of mammographic features, with prior studies suggesting that women with higher levels of breast asymmetry may be at elevated breast cancer risk. Increasingly, studies are recognizing the potential of bilateral breast asymmetry defined by mammographic breast density in determining breast cancer risk. Recently, Eriksson and colleagues highlighted a strong influence of breast asymmetry within a model they developed to predict short-term breast cancer risk among women attending breast screening. They observed that the contribution to the model of asymmetry in mammographic breast density, microcalcifications, and masses between the breasts was as substantial as the total number of microcalcifications and masses found within a mammogram, indicating that differences between the breasts may be an important risk marker. To help further understand associations between breast cancer risk factors and asymmetry of breast density, particularly among women at elevated risk for breast cancer, we evaluated risk factor relationships with the bilateral asymmetry of volumetric measures of global and local breast density across the spectrum of premalignant and invasive breast cancer diagnoses. Methods: This study included 882 women enrolled as part of the National Cancer Institute's Breast Radiology Evaluation and Study of Tissues (BREAST)-Stamp Project (2007-2010). The BREAST-Stamp Project is a cross-sectional molecular epidemiologic study that aims to understand how novel breast density measures are related to breast cancer etiology. Women were enrolled if they were referred for diagnostic image-guided breast biopsy following an abnormal mammogram at the University of Vermont Medical Center, and had not previously been diagnosed or treated for cancer, undergone breast surgery within one year or received chemoprevention. Risk factor data were collected at study enrolment via interview and self-administered questionnaires. Breast density measures were estimated using Single X-ray Absorptiometry (SXA), a technique in which an SXA breast density phantom was affixed to the compression paddle of the mammography machine during routine mammography so that it was included in the X-ray field. It served as a reference standard to estimate volumetric breast density. Breast density was assessed using pre-biopsy craniocaudal full-field digital mammograms of both the ipsilateral (affected) and contralateral (unaffected) breast. Firstly, global density from each laterality was determined as percent fibroglandular volume (%FGV). Secondly, localized volumetric density measures were estimated following identification of the biopsy site on the ipsilateral pre-biopsy mammogram by the study radiologist and identifying the corresponding site on the contralateral mammogram. The SXA estimated %FGV in a perilesional volume twice the size of, but excluding, the biopsy target, centered at the biopsy site. Previous estimates of reproducibility for the SXA test phantoms demonstrated a repeatability SD of 2%, with a ±2% accuracy for the entire thickness and density ranges. Breast density asymmetry was defined as an absolute bilateral difference in measures when subtracting the breast density measures of the contralateral breast from the ipsilateral measures. Spearman's correlations (rho) examined associations between breast density measures of the left and right breasts. To determine relationships between breast cancer risk factors (defined as categorical variables) and measures of bilateral breast density asymmetry, analysis of covariance (ANCOVA) models (PROC GLM) were used. Analyses were conducted at the per woman level using SAS. Probability values of &lt;0.05 were considered statistically significant, and all tests were two-tailed. Results:We initially investigated asymmetry within each woman by examining correlations between breast density measures in the left and right breasts. Strong, positive correlations between the ipsilateral and contralateral breast were observed for each breast density measure (rho for global %FGV=0.89, p-value&lt;0.0001; rho for local %FGV=0.79, p-value&lt;0.0001). Breast asymmetry was observed in the majority of the study population. For global %FGV, 76% of women had a bilateral difference ≥2%, with 43% of women having higher %FGV in their ipsilateral affected breast and 33% having higher in their contralateral unaffected breast. For localized %FGV, the majority of women had differences between their two breasts (89%), with 61% of women having higher localized %FGV in their ipsilateral affected breast compared to the remaining 28% who had higher localized breast density in their unaffected breast. We next examined relationships between breast cancer risk factors and breast asymmetry. Overall, no associations were observed between any of the risk factors examined, including age, race, body mass index, education, menopausal status, menopausal hormone therapy use with absolute bilateral differences in global or localized %FGV. Among the study population, most women had a benign breast disease diagnosis, with 33% and 43% being diagnosed with benign non-proliferative and benign proliferative lesions, respectively. Of the study population, 15% were diagnosed with invasive breast cancer. Overall, no differences were observed in bilateral differences in global %FGV according to diagnosis; however, higher mean bilateral differences in localized %FGV were observed for women with invasive compared to other diagnoses including benign and in-situ lesions (p=0.056). Discussion and conclusions: Our findings showed that breast asymmetry, defined by bilateral differences in global and localized mammographic breast density, was mostly unrelated to breast cancer risk factors among women undergoing an image guided breast biopsy. We observed that localized measures, defined according to within-woman bilateral differences in localized %FGV surrounding a suspicious lesion as compared with localized %FVG in a comparable location in the contralateral breast, may be an indication of cancer. This investigation is currently ongoing and efforts are underway to replicate findings using evolving image analysis methods such as Volpara Density Maps, an FDA-approved breast imaging tool which provides volumetric estimates of local glandular tissue distribution. Further, the ascertainment of 10-year follow-up data within this study population is in progress, which will facilitate prospective investigations of the relationship between breast asymmetry and breast cancer risk. Ongoing work will also extend our understanding of whether breast asymmetry is related to individualized breast cancer risk, defined using tailored breast cancer risk assessment tools. In conclusion, further understanding of breast asymmetry is needed to better exploit how bilateral differences in mammographic features may be used to inform breast cancer etiology as well as future breast cancer risk.

Citation Format: Maeve Mullooly, Shaoqi Fan, Ruth M. Pfeiffer, Brian Sprague, Pamela M. Vacek, Donald L. Weaver, John A. Shepherd, Amir Pasha Mahmoudzadeh, Jeff Wang, Serghei Malkov, Jason M. Johnson, Sally D. Herschorn, Gretchen L. Gierach. Investigation of relationships between breast cancer risk factors and bilateral mammographic breast density asymmetry among women undergoing diagnostic image-guided breast biopsies [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr NG15.

Abstract 5805: Treatment-associated endocrine symptoms and change in ultrasound tomography measures of breast density after tamoxifen therapy

Background: Tamoxifen therapy has been shown to have greater therapeutic benefit among women whose breast density declines subsequent to treatment than among women whose density does not decline. Although limited data suggests that endocrine symptoms after tamoxifen initiation may be associated with improved breast cancer outcomes, it is unknown whether these symptoms are associated with reductions in breast density. We therefore evaluated endocrine symptoms and change in breast density in a 12-month longitudinal study of women undergoing tamoxifen therapy for clinical indications.

Methods: Cohort members (N=74) were aged 30-74 years in the Ultrasound Study of Tamoxifen at Karmanos Cancer Institute and Henry Ford Health Systems (Detroit, MI). Endocrine symptoms and breast density were both assessed prior to tamoxifen initiation (T0) and at 1-3 months (T1), 4-6 months (T2), and approximately 12 months (T3) post-tamoxifen initiation. Treatment-associated endocrine symptoms included treatment-emergent or increasing vasomotor and/or joint symptoms. Endocrine symptom severity was also assessed with a Likert scale for symptom frequency and categorized as no symptoms (score=0), low/moderate symptoms (score=1-5), and high symptoms (score=6+). Sound speed (m/s), a surrogate of volumetric breast density, was measured with whole breast ultrasound tomography. Change in breast density was calculated as density at T1-T3 minus density at T0. We used multivariable linear regression to estimate mean change in density by endocrine symptoms adjusting for age, race, menopausal status, body mass index, and baseline sound speed. Generalized estimating equations were used to account for within-subject correlations over time.

Results: Women with treatment-associated endocrine symptoms had an overall greater mean reduction in breast density compared with women without symptoms (mean change [95% CI]: -1.97 m/s [-3.80, -0.13]; -0.27 m/s [- 3.50, 2.95], respectively; p=0.22). Longitudinal trends in breast density significantly differed for women with versus without treatment-associated endocrine symptoms (p-interaction=0.02). Significant declines in breast density over time were observed among women with treatment-associated endocrine symptoms (p-trend=0.005), but not among women without symptoms (p-trend=0.16). Similar trends in breast density decline were observed among women with higher symptom severity (p-trends for no symptoms=0.53; low/moderate symptoms=0.04; high symptoms=0.008).

Conclusions: These findings suggest that treatment-associated endocrine symptoms may be associated with a significant decline in breast density after tamoxifen initiation. Further studies are needed to assess whether these observations can predict clinical outcome, and if confirmed, both treatment-associated endocrine symptoms and observed reductions in breast density may be useful for patients and providers to improve adherence.

Citation Format: Cody Ramin, Ruth Pfeiffer, Shaoqi Fan, Maeve Mullooly, Roni T. Falk, Mark A. Sak, Michael S. Simon, David H. Gorski, Haythem Ali, Peter Littrup, Nebojsa Duric, Mark E. Sherman, Gretchen L. Gierach. Treatment-associated endocrine symptoms and change in ultrasound tomography measures of breast density after tamoxifen therapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5805.

Abstract 3488: Associations of circulating hormones with mammographic density in postmenopausal women referred to diagnostic breast biopsy

Introduction Elevated mammographic density (MD) is a strong and independent risk factor for breast cancer, though underlying mechanisms are unclear. Prior studies have suggested that increased cumulative exposure to sex-steroid hormones and growth factors may impact both MD and MD-related breast cancer risk; however, most studies have only evaluated individual hormones. In this study, we simultaneously explored the relationship between 29 circulating hormones and growth factors with MD among postmenopausal women undergoing diagnostic breast biopsy.

Methods We used data from 89 postmenopausal women, aged 44-65, who had complete measurements of 29 serum hormones from a single pre-biopsy blood draw (i.e., sex-steroid hormones: 15 estrogen/estrogen metabolites, 7 progesterone/progesterone metabolites; and non-sex hormones: insulin-like growth factor I and binding proteins (IGFBPs) 2-7). Volumetric MD (% fibroglandular volume) was assessed in pre-biopsy digital mammograms using single X-ray absorptiometry. Sufficient dimension reduction methods were used to compute a composite marker score that accommodates correlations among hormones and their relationship to MD. Backward elimination was applied to select log-transformed hormones contributing to the score at α=0.05; multivariable linear regression was used to further examine associations between selected hormones and MD within a single model, adjusting for age and BMI.

Results Pearson correlations between hormones were moderate-to-strong. Dimension reduction methods identified 6 hormones as associated with MD (p&lt;0.05): estradiol, 2-hydroxyestradiol, 2-methoxyestrone, 16-ketoestradiol, IGFBP-2, and 17α-hydroxyprogesterone, in models that considered MD as either continuous or dichotomous (&gt;median vs. ≤median); BMI was consistently identified as the most significant predictor of MD (P &lt;0.0001). In a multivariable linear regression model that included these 6 hormones, in addition to age and BMI, higher levels of 2-methoxyestrone, IGFBP-2, and 17α-hydroxyprogesterone were significantly associated with increased MD, whereas higher levels of age and BMI were significantly associated with lower MD.

Conclusions We identified 6 out of 29 correlated hormones that were significantly associated with MD among postmenopausal women. For several, the directions of their associations with MD were comparable to those observed in prior studies that have separately evaluated these hormones in relation to breast cancer risk. We plan to further explore how circulating hormones concurrently affect MD in premenopausal women, accounting for menstrual cycle phase. Incorporation of dimension reduction methods in studies of multiple correlated hormones can help uncover new etiologic insights into the role of hormones and growth factors in MD and breast carcinogenesis and inform strategies for prevention.

Citation Format: Shaoqi Fan, Ruth M. Pfeiffer, Manila Hada, Roni T. Falk, Maeve Mullooly, Hannah Oh, Berta Geller, Pamela Vacek, Donald Weave, John Shepherd, Jeff Wang, Sally Herschorn, Louise A. Brinton, Xia Xu, Mark E. Sherman, Britton Trabert, Gretchen L. Gierach. Associations of circulating hormones with mammographic density in postmenopausal women referred to diagnostic breast biopsy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3488.

Obesity and related conditions and risk of inflammatory breast cancer: a nested case-control study

PURPOSE

Inflammatory breast cancer (IBC) is a rare, poorly understood and aggressive tumor. We extended prior findings linking high body mass index (BMI) to substantial increased IBC risk by examining BMI associations before and after adjustment for well-characterized comorbidities using medical record data for diabetes, insulin resistance, and disturbances of cholesterol metabolism in a general community healthcare setting.

METHODS

We identified 247 incident IBC cases diagnosed at Kaiser Permanente Northern California between 2005 and 2017 and 2470 controls matched 10:1 on birth year and geographic area and with ≥ 13 months of continuous enrollment prior to diagnosis/index date. We assessed exposures from 6 years up to one year prior to the diagnosis/index date, using logistic regression to calculate odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Before adjustment for comorbidities, ORs (95% CIs) for BMI of 25-< 30, 30-< 35, and ≥ 35 compared to < 25 kg/m² were 1.5 (0.9-2.3), 2.0 (1.2-3.1), and 2.5 (1.4-4.4), respectively. After adjustment for pre-diabetes/diabetes, HDL-C and triglyceride levels, and dyslipidemia, corresponding ORs were 1.3 (0.8-2.1), 1.6 (0.9-2.9), and 1.9 (1.0-3.5). The OR for HDL-C levels < 50 mg/dL compared to ≥ 65 mg/dL was 2.0 (1.2-3.3) in the adjusted model. In a separate model the OR for a triglyceride/HDL-C ratio ≥ 2.50 compared to < 1.62 was 1.7 (1.1-2.8) after adjustment for BMI, pre-diabetes/diabetes, and dyslipidemia. Results did not differ significantly by estrogen receptor status.

CONCLUSIONS

Obesity and measures of insulin resistance independently increased IBC risk as did obesity and low HDL-C levels. These findings, if confirmed, have implications for IBC prevention.

Abstract A080: Associations between quantitative measures of TDLU involution and breast tumor molecular subtypes among breast cancer cases in the Black Women’s Health Study

Background: Terminal duct lobular units (TDLUs) are the structures in the breast that give rise to most breast cancers. Previous work has shown that TDLU involution is inversely associated with TDLU metrics, such as TDLU count/100mm2, TDLU span (μm), and number of acini/TDLU, and that these metrics may be elevated in the background normal breast tissue of women diagnosed with triple-negative (TN) compared with luminal A breast tumors. However, it is unknown if this relationship exists in black women, who have the highest incidence of TN breast cancer as well as the highest overall breast cancer mortality rate. We sought to determine the relationships of quantitative measures of TDLU involution with breast cancer molecular subtype among participants in the Black Women’s Health Study. Methods: We digitized hematoxylin and eosin stained normal adjacent tissues from TN (estrogen receptor negative (ER), progesterone receptor negative, and human epidermal growth factor 2 (HER2) negative; n=67) and luminal A (ER positive and HER2 negative; n=162) breast cancer cases from the Black Women’s Health Study. We used logistic regression to evaluate associations between TDLU metrics and breast cancer subtype (TN vs. luminal A), with adjustment for age and body mass index. We performed ordinal logistic regression to evaluate relationships between population and clinical characteristics and TDLU metrics. Results: Among the 229 breast cancer cases, mean age at diagnosis was 53.7 years; 68.7% of TN and 54.3% of luminal A cases were under 55 years of age. Most women had a body mass index (BMI) &gt;30kg/m2, were parous, did not smoke, and did not have a family history of breast cancer. The odds of TN breast cancer were elevated for the second and third tertiles of TDLU count relative to the first tertile, with odds ratios (95% confidence interval) of 2.89 (1.11, 4.86) and 1.92 (0.93, 4.08), respectively. Similarly, the odds of TN breast cancer increased with increasing tertiles of median TDLU span, with odds ratios of 2.25 (1.06, 4.91) and 2.38 (1.14, 5.15) for the second and third tertiles, respectively, compared to the first tertile. These associations persisted even after adjustment for age and BMI. No association was observed with median acini count/TDLU and TN breast cancer. We also observed significant associations of some breast cancer risk factors with measures of TDLU involution. Higher TDLU count was associated with younger age, more physical activity, lower BMI, current use of oral contraceptives or menopausal hormones, and premenopausal status. Conclusion: The associations of TDLU metrics with breast cancer subtype observed in this population of black women are consistent with previous studies of white and Asian women, with reduced TDLU involution in TN breast cancers compared with luminal A. Further investigation is needed to understand the factors that influence TDLU involution and the mechanisms that mediate TDLU involution and breast cancer subtype.

Citation Format: Brittny C Davis Lynn, Renata Cora, Ruth M Pfeiffer, Traci N Bethea, Gary Zirpoli, Julie R Palmer, Gretchen L Gierach. Associations between quantitative measures of TDLU involution and breast tumor molecular subtypes among breast cancer cases in the Black Women’s Health Study [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr A080.

Association of Circulating Progesterone With Breast Cancer Risk Among Postmenopausal Women

IMPORTANCE

The role of endogenous progesterone in the development of breast cancer remains largely unexplored to date, primarily owing to assay sensitivity limitations and low progesterone concentrations in postmenopausal women. Recently identified progesterone metabolites may provide insights as experimental data suggest that 5α-dihydroprogesterone (5αP) concentrations reflect cancer-promoting properties and 3α-dihydroprogesterone (3αHP) concentrations reflect cancer-inhibiting properties.

OBJECTIVE

To evaluate the association between circulating progesterone and progesterone metabolite levels and breast cancer risk.

DESIGN, SETTING, AND PARTICIPANTS

Using a sensitive liquid chromatography-tandem mass spectrometry assay, prediagnostic serum levels of progesterone and progesterone metabolites were quantified in a case-cohort study nested within the Breast and Bone Follow-up to the Fracture Intervention Trial (n = 15 595). Participation was limited to women not receiving exogenous hormone therapy at the time of blood sampling (1992-1993). Incident breast cancer cases (n = 405) were diagnosed during 12 follow-up years and a subcohort of 495 postmenopausal women were randomly selected within 10-year age and clinical center strata. Progesterone assays were completed in July 2017; subsequent data analyses were conducted between July 15, 2017, and December 20, 2018.

EXPOSURES

Circulating concentrations of pregnenolone, progesterone, and their major metabolites.

MAIN OUTCOMES AND MEASURES

Development of breast cancer, with hazard ratios (HRs) and 95% CIs was estimated using Cox proportional hazards regression adjusted for key confounders, including estradiol. Evaluation of hormone ratios and effect modification were planned a priori.

RESULTS

The present study included 405 incident breast cancer cases and a subcohort of 495 postmenopausal women; the mean (SD) age at the time of the blood draw was 67.2 (6.2) years. Progesterone concentrations were a mean (SD) of 4.6 (1.7) ng/dL. Women with higher circulating progesterone levels were at an increased risk for breast cancer per SD increase in progesterone levels (HR, 1.16; 95% CI, 1.00-1.35; P = .048). The association with progesterone was linear in a 5-knot spline and stronger for invasive breast cancers (n = 267) (HR, 1.24; 95% CI, 1.07-1.43; P = .004). Among women in the lowest quintile (Q1) of circulating estradiol (<6.30 pg/mL) elevated progesterone concentrations were associated with reduced breast cancer risk per SD increase in progesterone levels (HR, 0.38; 95% CI, 0.15-0.95; P = .04) and increased risk among women in higher quintiles of estradiol (Q2-Q5; ≥6.30 pg/mL) (HR, 1.18; 95% CI, 1.04-1.35; P = .01; P = .04 for interaction).

CONCLUSIONS AND RELEVANCE

In this case-cohort study of postmenopausal women, elevated circulating progesterone levels were associated with a 16% increase in the risk of breast cancer. Additional research should be undertaken to assess how postmenopausal breast cancer risk is associated with both endogenous progesterone and progesterone metabolites and their interactions with estradiol.

Application of convolutional neural networks to breast biopsies to delineate tissue correlates of mammographic breast density

Breast density, a breast cancer risk factor, is a radiologic feature that reflects fibroglandular tissue content relative to breast area or volume. Its histology is incompletely characterized. Here we use deep learning approaches to identify histologic correlates in radiologically-guided biopsies that may underlie breast density and distinguish cancer among women with elevated and low density. We evaluated hematoxylin and eosin (H&E)-stained digitized images from image-guided breast biopsies (n = 852 patients). Breast density was assessed as global and localized fibroglandular volume (%). A convolutional neural network characterized H&E composition. In total 37 features were extracted from the network output, describing tissue quantities and morphological structure. A random forest regression model was trained to identify correlates most predictive of fibroglandular volume (n = 588). Correlations between predicted and radiologically quantified fibroglandular volume were assessed in 264 independent patients. A second random forest classifier was trained to predict diagnosis (invasive vs. benign); performance was assessed using area under receiver-operating characteristics curves (AUC). Using extracted features, regression models predicted global (r = 0.94) and localized (r = 0.93) fibroglandular volume, with fat and non-fatty stromal content representing the strongest correlates, followed by epithelial organization rather than quantity. For predicting cancer among high and low fibroglandular volume, the classifier achieved AUCs of 0.92 and 0.84, respectively, with epithelial organizational features ranking most important. These results suggest non-fatty stroma, fat tissue quantities and epithelial region organization predict fibroglandular volume. The model holds promise for identifying histological correlates of cancer risk in patients with high and low density and warrants further evaluation.

Using Digital Pathology to Understand Epithelial Characteristics of Benign Breast Disease among Women Undergoing Diagnostic Image-Guided Breast Biopsy

Delayed terminal duct lobular unit (TDLU) involution is associated with elevated mammographic breast density (MD). Both are independent breast cancer risk factors among women with benign breast disease (BBD). Prior digital analyses of normal breast tissues revealed that epithelial nuclear density (END) and TDLU involution are inversely correlated. Accordingly, we examined associations of END, TDLU involution, and MD in BBD clinical biopsies. This study included digitized images of 262 representative image-guided hematoxylin and eosin-stained biopsies from 224 women diagnosed with BBD, enrolled within the cross-sectional BREAST-Stamp project that were visually assessed for TDLU involution (TDLU count/100 mm², median TDLU span and median acini count per TDLU). A digital algorithm estimated nuclei count per unit epithelial area, or END. Single X-ray absorptiometry of prebiopsy ipsilateral craniocaudal digital mammograms measured global and localized MD surrounding the biopsy region. Adjusted ordinal logistic regression models assessed relationships between tertiles of TDLU and END measures. Analysis of covariance examined mean differences in MD across END tertiles. TDLU measures were positively associated with increasing END tertiles [TDLU count/100 mm², OR_T3vsT1: 3.42, 95% confidence interval (CI), 1.87-6.28; acini count/TDLU_T3vsT1, OR: 2.40, 95% CI, 1.39-4.15]. END was significantly associated with localized, but not, global MD. Relationships were most apparent among patients with nonproliferative BBD. These findings suggest that quantitative END reflects different but complementary information to the histologic information captured by visual TDLU and radiologic MD measures and merits continued evaluation in assessing cellularity of breast parenchyma to understand the etiology of BBD.

Association of lifestyle and clinical characteristics with receipt of radiotherapy treatment among women diagnosed with DCIS in the NIH-AARP Diet and Health Study

PURPOSE

The long-term risks and benefits of radiotherapy for ductal carcinoma in situ (DCIS) remain unclear. Recent data from the Surveillance, Epidemiology and End Results (SEER) registries showed that DCIS-associated radiotherapy treatment significantly increased risk of second non-breast cancers including lung cancer. To help understand those observations and whether breast cancer risk factors are related to radiotherapy treatment decision-making, we examined associations between lifestyle and clinical factors with DCIS radiotherapy receipt.

METHODS

Among 1628 participants from the NIH-AARP Diet and Health Study, diagnosed with incident DCIS (1995-2011), we examined associations between lifestyle and clinical factors with radiotherapy receipt. Radiotherapy and clinical information were ascertained from state cancer registries. Odds ratios (ORs) and 95% confidence intervals (CIs) for radiotherapy receipt (yes/no) were estimated from multivariable logistic regression.

RESULTS

Overall, 45% (n = 730) received radiotherapy. No relationships were observed for most lifestyle factors and radiotherapy receipt, including current smoking (OR 0.97, 95%CI 0.70, 1.34). However positive associations were observed for moderate alcohol consumption and infrequent physical activity. The strongest associations were observed for radiotherapy receipt and more recent diagnoses (2005-2011 vs. 1995-1999; OR 1.60, 95%CI 1.14, 2.25), poorly versus well-differentiated tumors (OR 1.69, 95%CI 1.16, 2.46) and endocrine therapy (OR 3.37, 95%CI 2.56, 4.44).

CONCLUSIONS

Clinical characteristics were the strongest determinants of DCIS radiotherapy. Receipt was largely unrelated to lifestyle factors suggesting that the previously observed associations in SEER were likely not confounded by these lifestyle factors. Further studies are needed to understand mechanisms driving radiotherapy-associated second malignancies following DCIS, to identify prevention opportunities for this growing population.

Black-White Breast Cancer Incidence Trends: Effects of Ethnicity

Recent reports of converging black and white breast cancer incidence rates have gained much attention, potentially foreshadowing a worsening of the black-white breast cancer mortality disparity. However, these incidence rates also reflect the sum of non-Hispanics and Hispanics that may mask important ethnicity-specific trends. We therefore assessed race- and ethnicity-specific breast cancer trends using the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) 13 Registries Database (1992-2014). Age-period-cohort models projected rates for 2015-2030. Results confirmed merging of age-standardized incidence rates for blacks and whites circa 2012, but not for non-Hispanic black (NHB) and non-Hispanic white (NHW) women. Incidence rates were highest for NHW women (n = 382 290), followed by NHB women (n = 51 074), and then Hispanic white women (n = 48 651). The sample size for Hispanic blacks was too small for analysis (n = 693). Notably, future incidence rates are expected to slowly increase (2015 through 2030) among NHW women (0.24% per year, 95% confidence interval [CI] = 0.17 to 0.32) and slowly decrease for NHB women (-0.14% per year, 95% CI = -0.15 to -0.13). A putative worsening of the black-white mortality disparity, therefore, seems unlikely. Ethnicity matters when assessing race-specific breast cancer incidence rates.