The heritability of mammographic breast density and circulating sex-hormone levels: two independent breast cancer risk factors

Obesity-Dependent Association of the rs10454142 PPP1R21 with Breast Cancer

The purpose of this work was to find a link between the breast cancer (BC)-risk effects of sex hormone-binding globulin (SHBG)-associated polymorphisms and obesity. The study was conducted on a sample of 1498 women (358 BC; 1140 controls) who, depending on the presence/absence of obesity, were divided into two groups: obese (119 BC; 253 controls) and non-obese (239 BC; 887 controls). Genotyping of nine SHBG-associated single nucleotide polymorphisms (SNP)-rs17496332 PRMT6, rs780093 GCKR, rs10454142 PPP1R21, rs3779195 BAIAP2L1, rs440837 ZBTB10, rs7910927 JMJD1C, rs4149056 SLCO1B1, rs8023580 NR2F2, and rs12150660 SHBG-was executed, and the BC-risk impact of these loci was analyzed by logistic regression separately in each group of obese/non-obese women. We found that the BC-risk effect correlated by GWAS with the SHBG-level polymorphism rs10454142 PPP1R21 depends on the presence/absence of obesity. The SHBG-lowering allele C rs10454142 PPP1R21 has a risk value for BC in obese women (allelic model: CvsT, OR = 1.52, 95%CI = 1.10-2.11, and pperm = 0.013; additive model: CCvsTCvsTT, OR = 1.71, 95%CI = 1.15-2.62, and pperm = 0.011; dominant model: CC + TCvsTT, OR = 1.95, 95%CI = 1.13-3.37, and pperm = 0.017) and is not associated with the disease in women without obesity. SNP rs10454142 PPP1R21 and 10 proxy SNPs have adipose-specific regulatory effects (epigenetic modifications of promoters/enhancers, DNA interaction with 51 transcription factors, eQTL/sQTL effects on five genes (PPP1R21, RP11-460M2.1, GTF2A1L, STON1-GTF2A1L, and STON1), etc.), can be "likely cancer driver" SNPs, and are involved in cancer-significant pathways. In conclusion, our study detected an obesity-dependent association of the rs10454142 PPP1R21 with BC in women.

Sex-Hormone-Binding Globulin Gene Polymorphisms and Breast Cancer Risk in Caucasian Women of Russia

In our work, the associations of GWAS (genome-wide associative studies) impact for sex-hormone-binding globulin (SHBG)-level SNPs with the risk of breast cancer (BC) in the cohort of Caucasian women of Russia were assessed. The work was performed on a sample of 1498 women (358 BC patients and 1140 control (non BC) subjects). SHBG correlated in previously GWAS nine polymorphisms such as rs780093 GCKR, rs17496332 PRMT6, rs3779195 BAIAP2L1, rs10454142 PPP1R21, rs7910927 JMJD1C, rs4149056 SLCO1B1, rs440837 ZBTB10, rs12150660 SHBG, and rs8023580 NR2F2 have been genotyped. BC risk effects of allelic and non-allelic SHBG-linked gene SNPs interactions were detected by regression analysis. The risk genetic factor for BC developing is an SHBG-lowering allele variant C rs10454142 PPP1R21 ([additive genetic model] OR = 1.31; 95%CI = 1.08-1.65; pperm = 0.024; power = 85.26%), which determines 0.32% of the cancer variance. Eight of the nine studied SHBG-related SNPs have been involved in cancer susceptibility as part of nine different non-allelic gene interaction models, the greatest contribution to which is made by rs10454142 PPP1R21 (included in all nine models, 100%) and four more SNPs-rs7910927 JMJD1C (five models, 55.56%), rs17496332 PRMT6 (four models, 44.44%), rs780093 GCKR (four models, 44.44%), and rs440837 ZBTB10 (four models, 44.44%). For SHBG-related loci, pronounced functionality in the organism (including breast, liver, fibroblasts, etc.) was predicted in silico, having a direct relationship through many pathways with cancer pathophysiology. In conclusion, our results demonstrated the involvement of SHBG-correlated genes polymorphisms in BC risk in Caucasian women in Russia.

Cross-ancestry Genome-wide Association Studies of Sex Hormone Concentrations in Pre- and Postmenopausal Women

OBJECTIVE

Concentrations of circulating sex hormones have been associated with a variety of diseases in women and are strongly influenced by menopausal status. We investigated the genetic architectures of circulating concentrations of estradiol, testosterone, and SHBG by menopausal status in women of European and African ancestry.

METHODS

Using data on 229 966 women from the UK Biobank, we conducted genome-wide association studies (GWASs) of circulating concentrations of estradiol, testosterone, and SHBG in premenopausal and postmenopausal women. We tested for evidence of heterogeneity of genetic effects by menopausal status and genetic ancestry. We conducted gene-based enrichment analyses to identify tissues in which genes with GWAS-enriched signals were expressed.

RESULTS

We identified 4 loci (5q35.2, 12q14.3, 19q13.42, 20p12.3) that were associated with detectable concentrations of estradiol in both pre- and postmenopausal women of European ancestry. Heterogeneity analysis identified 1 locus for testosterone (7q22.1) in the CYP3A7 gene and 1 locus that was strongly associated with concentrations of SHBG in premenopausal women only (10q15.1) near the AKR1C4 gene. Gene-based analysis of testosterone revealed evidence of enrichment of GWAS signals in genes expressed in adipose tissue for postmenopausal women. We did not find any evidence of ancestry-specific genetic effects for concentrations of estradiol, testosterone, or SHBG.

CONCLUSIONS

We identified specific loci that showed genome-wide significant evidence of heterogeneity by menopausal status for testosterone and SHBG. We also observed support for a more prominent role of genetic variants located near genes expressed in adipose tissue in determining testosterone concentrations among postmenopausal women.

Heterogenous Effect of Risk Factors on Breast Cancer across the Breast Density Categories in a Korean Screening Population

We evaluated the heterogeneity of the effect of known risk factors on breast cancer development based on breast density by using the Breast Imaging-Reporting and Data System (BI-RADS). In total, 4,898,880 women, aged 40-74 years, who participated in the national breast cancer screening program in 2009-2010 were followed up to December 2018. Increased age showed a heterogeneous association with breast cancer (1-year hazard ratio (HR) = 0.92, 1.00 (reference), 1.03, and 1.03 in women with BI-RADS density category 1, 2, 3, and 4, respectively; P-heterogeneity < 0.001). More advanced age at menopause increased breast cancer risk in all BI-RADS categories. This was more prominent in women with BI-RADS density category 1 but less prominent in women in other BI-RADS categories (P-heterogeneity = 0.009). In postmenopausal women, a family history of breast cancer, body mass index ≥ 25 kg/m², and smoking showed a heterogeneous association with breast cancer across all BI-RADS categories. Other risk factors including age at menarche, menopause, hormone replacement therapy after menopause, oral contraceptive use, and alcohol consumption did not show a heterogeneous association with breast cancer across the BI-RADS categories. Several known risk factors of breast cancer had a heterogeneous effect on breast cancer development across breast density categories, especially in postmenopausal women.

No genetic contribution to variation in human offspring sex ratio: a total population study of 4.7 million births

The ratio of males to females among an individual's offspring at birth (offspring sex ratio) has long been of great interest to evolutionary biologists. The human offspring sex ratio is around 1 : 1 and is understood primarily in terms of Fisher's principle (R. A. Fisher, The genetical theory of natural selection, 1930), which is based on the insight that in a population with an unequal sex ratio, each individual of the rarer sex will on average have greater reproductive value than each individual of the more common sex. Accordingly, individuals genetically predisposed to produce the rarer sex will tend to have greater fitness and thus genes predisposing to bearing that sex will increase in frequency until the population sex ratio approaches 1 : 1. An assumption of this perspective is that individuals' offspring sex ratio is heritable. However, the heritability in humans remains remarkably uncertain, with inconsistent findings and important power limitations of existing studies. To address this persistent uncertainty, we used data from the entire Swedish-born population born 1932 or later, including 3 543 243 individuals and their 4 753 269 children. To investigate whether offspring sex ratio is influenced by genetic variation, we tested the association between individuals' offspring's sex and their siblings' offspring's sex (n pairs = 14 015 421). We estimated that the heritability for offspring sex ratio was zero, with an upper 95% confidence interval of 0.002, rendering Fisher's principle and several other existing hypotheses untenable as frameworks for understanding human offspring sex ratio.

Interaction Effect Between Breast Density and Reproductive Factors on Breast Cancer Risk in Korean Population

Background

This study was conducted to explore the effect of known risk factors, focusing on risk factors including age at menarche, age at menopause, number of children, family history of breast cancer, and age at first birth according to breast density, in consideration of interaction among East-Asian women.

Methods

Case-control study with 2,123 cases and 2,121 controls with mammographic density was conducted. Using the mammographic film, breast density was measured using Breast Imaging-Reporting and Data System. To identify the association of selected reproductive factors including age at menarche, age at menopause, number of children, family history of breast cancer, and age at first birth according to breast density, stratified analysis was conducted according to breast density groups and interaction effects was assessed. The results were presented with adjusted OR and 95% CIs.

Results

Significant interaction effect between age at first birth and breast density on breast cancer (P = 0.048) was observed. Women with age at first birth ≥ 28 years old showed increased breast cancer risk in extremely dense breast group (≥ 75%) (OR = 1.627, 95% CI = 1.190–2.226). However, women with fatty breast (< 50%) and heterogeneously dense breast (50%–75%) did not show an increased association. Age at menarche, age at menopause, number of children, and family history of breast cancer did not show significant interaction with breast cancer and similar risk patterns were observed.

Conclusions

Age at first birth showed significant interaction with breast density on breast cancer risk. Further studies considering biologically plausable model between exposure, intermediate outcomes and breast cancer risk with prospective design need to be undertaken in East Asian women.

Mammographic Density and Circulating Sex Hormones: a Cross-Sectional Study in Postmenopausal Korean Women

Mammographic density (MD) is a strong independent risk factor for breast cancer. It has been suggested that breast cancer is related to the exposure to circulating sex hormones. However, relations between MD and hormones have been inconsistent. In addition, such relations are mainly evaluated in Western populations. Therefore, we conducted a cross-sectional study in 396 cancer-free postmenopausal Korean women who had never used hormone replacement therapy. We assayed estradiol, testosterone, and sex hormone-binding globulin (SHBG) levels. We then calculated free testosterone (cFT) levels. Total and dense areas of digital mammogram were measured using a computer-assisted thresholding method, and non-dense area and percent dense area were calculated. Linear mixed model was used for analyses. Estradiol and testosterone levels were not associated with any MD measures after adjusting for reproductive factors and body mass index. However, cFT was persistently associated with non-dense area even after adjusting for covariates, with non-dense area increased by 3.5% per 1 standard deviation increase of cFT. SHBG showed an inverse association with non-dense area, although it showed a positive association with dense area and percent dense area regardless of adjustment for covariates. Non-dense area was decreased by 5.6% while percent dense area was increased by 13.4% per 1 standard deviation increase of SHBG. These findings suggest that SHBG might be related with breast cancer risk, probably through its association with breast density.

Elevated Aromatase (CYP19A1) Expression Is Associated with a Poor Survival of Patients with Estrogen Receptor Positive Breast Cancer

Genetic variants in CYP19A1, the gene encoding aromatase, have been reported to be associated with circulating estrogen concentrations, a key risk factor for breast cancer. The mechanism underlying this association is still unclear; it has been suggested that some of these variants may alter the expression and/or activity of aromatase. Here we analyzed the expression of intra-tumoral CYP19A1 messenger RNA (mRNA) and the genotypes of rs10046, a well-characterized single nucleotide polymorphism in CYP19A1, in 138 breast cancer patients and 15 breast cancer cell lines. The genotype TT was detected in 36 patients and six cell lines, genotype CT in 55 patients and five cell lines, and genotype CC in 28 patients and four cell lines. We found no evidence for a significant association of CYP19A1 levels with rs10046 genotypes, although expression tended to be higher in tumors and cell lines with the homozygous risk genotype TT. We also found no evidence for a significant association of rs10046 genotypes with breast cancer prognosis. In contrast, high CYP19A1 expression was highly significantly associated with a poor overall, disease-free, and metastasis-free survival in estrogen receptor-positive but not negative breast cancer patients. Moreover, CYP19A1 mRNA was significantly elevated in postmenopausal patients and in patients older than 50 years, and a trend towards a positive correlation with ER status and ESR1 mRNA expression was observed. These findings highlight the key role of aromatase in estrogen receptor-positive breast cancer biology.

CYP19A1 fine-mapping and Mendelian randomization: estradiol is causal for endometrial cancer

Candidate gene studies have reported CYP19A1 variants to be associated with endometrial cancer and with estradiol (E2) concentrations. We analyzed 2937 single nucleotide polymorphisms (SNPs) in 6608 endometrial cancer cases and 37 925 controls and report the first genome wide-significant association between endometrial cancer and a CYP19A1 SNP (rs727479 in intron 2, P=4.8×10(-11)). SNP rs727479 was also among those most strongly associated with circulating E2 concentrations in 2767 post-menopausal controls (P=7.4×10(-8)). The observed endometrial cancer odds ratio per rs727479 A-allele (1.15, CI=1.11-1.21) is compatible with that predicted by the observed effect on E2 concentrations (1.09, CI=1.03-1.21), consistent with the hypothesis that endometrial cancer risk is driven by E2. From 28 candidate-causal SNPs, 12 co-located with three putative gene-regulatory elements and their risk alleles associated with higher CYP19A1 expression in bioinformatical analyses. For both phenotypes, the associations with rs727479 were stronger among women with a higher BMI (Pinteraction=0.034 and 0.066 respectively), suggesting a biologically plausible gene-environment interaction.

Incorporating Biomarkers in Studies of Chemoprevention

Despite Food and Drug Administration approval of tamoxifen and raloxifene for breast cancer risk reduction and endorsement by multiple agencies, uptake of these drugs for primary prevention in the United States is only 4% for risk eligible women likely to benefit from their use. Side effects coupled with incomplete efficacy and lack of a survival advantage are the likely reasons. This disappointing uptake, after the considerable effort and expense of large Phase III cancer incidence trials required for approval, suggests that a new paradigm is required. Current prevention research is focused on (1) refining risk prediction, (2) exploring behavioral and natural product interventions, and (3) utilizing novel translational trial designs for efficacy. Risk biomarkers will play a central role in refining risk estimates from traditional models and selecting cohorts for prevention trials. Modifiable risk markers called surrogate endpoint or response biomarkers will continue to be used in Phase I and II prevention trials to determine optimal dose or exposure and likely effectiveness from an intervention. The majority of Phase II trials will continue to assess benign breast tissue for response and mechanism of action biomarkers. Co-trials are those in which human and animal cohorts receive the same effective dose and the same tissue biomarkers are assessed for modulation due to the intervention, but then additional animals are allowed to progress to cancer development. These collaborations linking biomarker modulation and cancer prevention may obviate the need for cancer incidence trials for non-prescription interventions.

Family resemblance of bone turnover rate in mothers and daughters--the MODAM study

We studied bone turnover markers (BTM) and bone microarchitecture (using high-resolution peripheral quantitative computed tomography (HR-pQCT)) in 171 postmenopausal women and their 210 premenopausal daughters. BTM levels correlated positively between mothers and daughters. The mother-daughter pairs with high BTM levels had lower cortical density than those with low BTM levels.

INTRODUCTION

We assessed the correlation of serum bone turnover markers (BTM) between postmenopausal mothers and their premenopausal daughters as well as possible determinants of this association and its impact on resemblance of bone microarchitecture between mothers and their daughters.

METHODS

Cross-sectional analysis was performed in 171 untreated postmenopausal mothers (54 sustained fragility fractures) and their 210 premenopausal daughters. Intact N-terminal propeptide of type I collagen (PINP) and β-isomerized C-terminal crosslinking telopeptide of type I collagen (CTX-I) were measured in the fasting status. Bone microarchitecture was assessed using HR-pQCT.

RESULTS

After adjustment for age, weight, lifestyle factors, hormones, and mother's fracture status, BTM levels correlated positively between mothers and daughters (Intraclass Correlation Coefficient = 0.22-0.27, p <0.005). Average BTM levels were ∼ 0.6 SD higher among daughters of mothers in the highest BTM quartile vs. the ones in the lowest BTM quartile. The variability of BTM levels explained ≤ 10 and ≤ 14% of variability of bone microarchitecture in the daughters and mothers, respectively. Cortical density was lower by 2.3-2.9% (0.6 SD, p <0.05 to <0.005) in the daughters from the mother-daughter pairs with high BTM levels (defined by generation-specific quartiles) than in the daughters from the pairs with low BTM levels. Corresponding differences for the mothers were 4.5-4.8% (0.5 SD, p <0.05 to <0.01).

CONCLUSION

BTM levels correlated between postmenopausal mothers and their premenopausal daughters after adjustment for age, weight, mother's fracture status, lifestyle, and hormonal factors. Family resemblance of BTM levels may contribute to family resemblance of some bone microarchitectural parameters, especially of cortical density.

Involvement of NF-κB and HSP70 signaling pathways in the apoptosis of MDA-MB-231 cells induced by a prenylated xanthone compound, α-mangostin, from Cratoxylum arborescens

Background

Cratoxylum arborescens has been used traditionally in Malaysia for the treatment of various ailments.

Methods

α-Mangostin (AM) was isolated from C. arborescens and its cell death mechanism was investigated. AM-induced cytotoxicity was observed with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Acridine orange/propidium iodide staining and annexin V were used to detect cells in early phases of apoptosis. High-content screening was used to observe the nuclear condensation, cell permeability, mitochondrial membrane potential, and cytochrome c release. The role of caspases-3/7, -8, and -9, reactive oxygen species, Bcl-2 and Bax expression, and cell cycle arrest were also investigated. To determine the role of the central apoptosis-related proteins, a protein array followed by immunoblot analysis was conducted. Moreover, the involvement of nuclear factor-kappa B (NF-κB) was also analyzed.

Results

Apoptosis was confirmed by the apoptotic cells stained with annexin V and increase in chromatin condensation in nucleus. Treatment of cells with AM promoted cell death-transducing signals that reduced MMP by downregulation of Bcl-2 and upregulation of Bax, triggering cytochrome c release from the mitochondria to the cytosol. The released cytochrome c triggered the activation of caspase-9 followed by the executioner caspase-3/7 and then cleaved the PARP protein. Increase of caspase-8 showed the involvement of extrinsic pathway. AM treatment significantly arrested the cells at the S phase (P<0.05) concomitant with an increase in reactive oxygen species. The protein array and Western blotting demonstrated the expression of HSP70. Moreover, AM significantly blocked the induced translocation of NF-κB from cytoplasm to nucleus.

Conclusion

Together, the results demonstrate that the AM isolated from C. arborescens inhibited the proliferation of MDA-MB-231 cells, leading to cell cycle arrest and programmed cell death, which was suggested to occur through both the extrinsic and intrinsic apoptosis pathways with involvement of the NF-κB and HSP70 signaling pathways.

α-Mangostin from Cratoxylum arborescens demonstrates apoptogenesis in MCF-7 with regulation of NF-κB and Hsp70 protein modulation in vitro, and tumor reduction in vivo

Cratoxylum arborescens is an equatorial plant belonging to the family Guttiferae. In the current study, α-Mangostin (AM) was isolated and its cell death mechanism was studied. HCS was undertaken to detect the nuclear condensation, mitochondrial membrane potential, cell permeability, and the release of cytochrome c. An investigation for reactive oxygen species formation was conducted using fluorescent analysis. To determine the mechanism of cell death, human apoptosis proteome profiler assay was conducted. In addition, using immunofluorescence and immunoblotting, the levels of Bcl-2-associated X protein (Bax) and B-cell lymphoma (Bcl)-2 proteins were also tested. Caspaces such as 3/7, 8, and 9 were assessed during treatment. Using HCS and Western blot, the contribution of nuclear factor kappa-B (NF-κB) was investigated. AM had showed a selective cytotoxicity toward the cancer cells with no toxicity toward the normal cells even at 30 μg/mL, thereby indicating that AM has the attributes to induce cell death in tumor cells. The treatment of MCF-7 cells with AM prompted apoptosis with cell death-transducing signals. This regulated the mitochondrial membrane potential by down-regulation of Bcl-2 and up-regulation of Bax, thereby causing the release of cytochrome c from the mitochondria into the cytosol. The liberation of cytochrome c activated caspace-9, which, in turn, activated the downstream executioner caspace-3/7 with the cleaved poly (ADP-ribose) polymerase protein, thereby leading to apoptotic alterations. Increase of caspace 8 had showed the involvement of an extrinsic pathway. This type of apoptosis was suggested to occur through both extrinsic and intrinsic pathways and prevention of translocation of NF-κB from the cytoplasm to the nucleus. Our results revealed AM prompt apoptosis of MCF-7 cells through NF-κB, Bax/Bcl-2 and heat shock protein 70 modulation with the contribution of caspaces. Moreover, ingestion of AM at (30 and 60 mg/kg) significantly reduced tumor size in an animal model of breast cancer. Our results suggest that AM is a potentially useful agent for the treatment of breast cancer.

Inclusion of endogenous hormone levels in risk prediction models of postmenopausal breast cancer

PURPOSE

Endogenous hormones are risk factors for postmenopausal breast cancer, and their measurement may improve our ability to identify high-risk women. Therefore, we evaluated whether inclusion of plasma estradiol, estrone, estrone sulfate, testosterone, dehydroepiandrosterone sulfate, prolactin, and sex hormone-binding globulin (SHBG) improved risk prediction for postmenopausal invasive breast cancer (n = 437 patient cases and n = 775 controls not using postmenopausal hormones) in the Nurses' Health Study.

METHODS

We evaluated improvement in the area under the curve (AUC) for 5-year risk of invasive breast cancer by adding each hormone to the Gail and Rosner-Colditz risk scores. We used stepwise regression to identify the subset of hormones most associated with risk and assessed AUC improvement; we used 10-fold cross validation to assess model overfitting.

RESULTS

Each hormone was associated with breast cancer risk (odds ratio doubling, 0.82 [SHBG] to 1.37 [estrone sulfate]). Individual hormones improved the AUC by 1.3 to 5.2 units relative to the Gail score and 0.3 to 2.9 for the Rosner-Colditz score. Estrone sulfate, testosterone, and prolactin were selected by stepwise regression and increased the AUC by 5.9 units (P = .003) for the Gail score and 3.4 (P = .04) for the Rosner-Colditz score. In cross validation, the average AUC change across the validation data sets was 6.0 (P = .002) and 3.0 units (P = .03), respectively. Similar results were observed for estrogen receptor-positive disease (selected hormones: estrone sulfate, testosterone, prolactin, and SHBG; change in AUC, 8.8 [P < .001] for Gail score and 5.8 [P = .004] for Rosner-Colditz score).

CONCLUSION

Our results support that endogenous hormones improve risk prediction for invasive breast cancer and could help identify women who may benefit from chemoprevention or more screening.

Aromatase inhibitor-induced modulation of breast density: clinical and genetic effects

Background:

Change in breast density may predict outcome of women receiving adjuvant hormone therapy for breast cancer. We performed a prospective clinical trial to evaluate the impact of inherited variants in genes involved in oestrogen metabolism and signalling on change in mammographic percent density (MPD) with aromatase inhibitor (AI) therapy.

Methods:

Postmenopausal women with breast cancer who were initiating adjuvant AI therapy were enrolled onto a multicentre, randomised clinical trial of exemestane vs letrozole, designed to identify associations between AI-induced change in MPD and single-nucleotide polymorphisms in candidate genes. Subjects underwent unilateral craniocaudal mammography before and following 24 months of treatment.

Results:

Of the 503 enrolled subjects, 259 had both paired mammograms at baseline and following 24 months of treatment and evaluable DNA. We observed a statistically significant decrease in mean MPD from 17.1 to 15.1% (P<0.001), more pronounced in women with baseline MPD ⩾20%. No AI-specific difference in change in MPD was identified. No significant associations between change in MPD and inherited genetic variants were observed.

Conclusion:

Subjects with higher baseline MPD had a greater average decrease in MPD with AI therapy. There does not appear to be a substantial effect of inherited variants in biologically selected candidate genes.

Mammographic breast density response to aromatase inhibition

PURPOSE

Mammographic breast density (MBD) is decreased by tamoxifen, but the effect of aromatase inhibitors is less clear.

EXPERIMENTAL DESIGN

We enrolled early-stage postmenopausal patients with breast cancer initiating adjuvant aromatase inhibitor therapy and ascertained mammograms before and at an average 10 months of aromatase inhibitor therapy. We matched cases to healthy postmenopausal women (controls) from a large mammography screening cohort on age, baseline body mass index, baseline MBD, and interval between mammograms. We estimated change in MBD using a computer-assisted thresholding program (Cumulus) and compared differences between cases and matched controls.

RESULTS

In predominantly White women (96%), we found 14% of the 387 eligible cases had a MBD reduction of at least 5% after an average of 10 months of aromatase inhibitor therapy. MBD reductions were associated with higher baseline MBD, aromatase inhibitor use for more than 12 months, and prior postmenopausal hormone use. Comparing each case with her matched control, there was no evidence of an association of change in MBD with aromatase inhibitor therapy [median case-control difference among 369 pairs was -0.1% (10th and 90th percentile: -5.9%, 5.2%) P = 0.51]. Case-control differences were similar by type of aromatase inhibitor (P's 0.41 and 0.56); prior use of postmenopausal hormones (P = 0.85); baseline MBD (P = 0.55); and length of aromatase inhibitor therapy (P = 0.08).

CONCLUSIONS

In postmenopausal women treated with aromatase inhibitors, 14% of cases had a MBD reduction of more than 5%, but these decreases did not differ from matched controls. These data suggest that MBD is not a clinically useful biomarker for predicting the value of aromatase inhibitor therapy in White postmenopausal women.