Epidemiology of basal-like breast cancer

Lack of evidence for KRAS oncogenic mutations in triple-negative breast cancer

Background

Mutational analysis of the KRAS gene has recently been established as a complementary in vitro diagnostic tool for the identification of patients with colorectal cancer who will not benefit from anti-epidermal growth factor receptor (EGFR) therapies. Assessment of the mutation status of KRAS might also be of potential relevance in other EGFR-overexpressing tumors, such as those occurring in breast cancer. Although KRAS is mutated in only a minor fraction of breast tumors (5%), about 60% of the basal-like subtype express EGFR and, therefore could be targeted by EGFR inhibitors. We aimed to study the mutation frequency of KRAS in that subtype of breast tumors to provide a molecular basis for the evaluation of anti-EGFR therapies.

Methods

Total, genomic DNA was obtained from a group of 35 formalin-fixed paraffin-embedded, triple-negative breast tumor samples. Among these, 77.1% (27/35) were defined as basal-like by immunostaining specific for the established surrogate markers cytokeratin (CK) 5/6 and/or EGFR. KRAS mutational status was determined in the purified DNA samples by Real Time (RT)-PCR using primers specific for the detection of wild-type KRAS or the following seven oncogenic somatic mutations: Gly12Ala, Gly12Asp, Gly12Arg, Gly12Cys, Gly12Ser, Gly12Val and Gly13Asp.

Results

We found no evidence of KRAS oncogenic mutations in all analyzed tumors.

Conclusions

This study indicates that KRAS mutations are very infrequent in triple-negative breast tumors and that EGFR inhibitors may be of potential benefit in the treatment of basal-like breast tumors, which overexpress EGFR in about 60% of all cases.

Interaction between menopausal status and obesity in affecting breast cancer risk

Obesity has a complex relationship to breast cancer risk that differs in premenopausal and postmenopausal women. Before the menopause, the level of adiposity is inversely related to risk, indicative of a protective effect, whereas in postmenopausal women, particularly the elderly, the association is a positive one, consistent with obesity being a risk factor. The importance of high estrogen production in adipose tissue, with consequent elevation of circulating biologically available estradiol, in the promotional effect of obesity on postmenopausal breast carcinogenesis is well established; the resulting tumors express both estrogen and progesterone receptors. The mechanism(s) for the protective effect in premenopausal women is less well understood, but the breast cancers that do develop in the presence of obesity are most often estrogen and progesterone receptor negative, consistent with the selection of non-estrogen-dependent tumor cells which are dependent on growth factors such as insulin, insulin-like growth factor-I and some adipokines. The influence of menopausal status on the relationships between adiposity and breast cancer appears to be modified within each category by age; the protective effect before the menopause may be limited to younger women (<35 years), and the adverse effect was found to apply specifically to older postmenopausal women. Although randomized trials of weight reduction for postmenopausal breast cancer prevention have not been performed, observational studies suggested that risk reduction does occur; in addition, other health benefits of weight control need to be considered regardless of menopausal status.

Triple negative breast cancers: clinical and prognostic implications

Triple negative breast cancers are defined by the absence of oestrogen, progesterone and HER2 expression. Most triple negative cancers display distinct clinical and pathological characteristics with a high proportion of these tumours occurring at a younger age of onset and in African-American women. Triple negative tumours typically demonstrate high histological grade and are the most common breast cancer subtype in BRCA1 carriers. In addition, many of the features of triple negative cancers are similar to those identified in the basal-like molecular subtype which has recently been characterised by gene expression profiling. Although the two groups overlap, they are not synonymous. Triple negative breast cancers are of pivotal clinical importance given the lack of therapeutic options. The prognostic significance of triple negative tumours remains unclear since the group is heterogeneous and worst prognosis seems to be mostly confined to those that express basal cytokeratins or epidermal growth factor receptor (EGFR). This review focuses on outlining the pathological, molecular, and clinical features of triple negative breast cancers, discusses its prognostic value and summarises current therapeutic approaches and future directions of research.

Clinical relevance of the triple-negative breast cancer concept: genetic basis and clinical utility of the concept

The beginning of microarray technology in the 1990s and the sequencing of the human genome in 2000 paved the way for the seminal paper of the Stanford group on the molecular portraits of human breast tumours in the same year. They described four distinct breast cancer subtypes, which they called 'luminal', 'basal', 'HER2-positive', and 'normal breast-like', based on unique gene expression patterns. This paper caused a paradigm shift. Breast cancer was no longer hormone receptor-positive or -negative, but rather luminal, basal or HER2-positive. Since then, numerous papers have appeared, trying to further characterise these subtypes on the DNA, RNA and protein level. Other groups have focussed on the epidemiology, prognosis and outcome after therapy of breast cancer patients according to these molecular subtypes. A promising prognostic marker within the subgroup of basal-like breast cancer is an up-regulated immune response, which is associated with favourable outcome. In addition, the majority of basal-like breast cancers harbour traits of a DNA damage repair defect. This feature can be exploited by the use of DNA damaging agents, and first exciting clinical results of the combination of carboplatin, gemcitabine and a poly (ADP-ribose) polymerase 1 (PARP-1) inhibitor have recently been reported. In this review, the molecular characterisation of triple-negative breast cancer, a proxy for basal-like breast cancer, is described and findings have been put into clinical context.

Use of four biomarkers to evaluate the risk of breast cancer subtypes in the women's contraceptive and reproductive experiences study

Epidemiologic studies suggest that some hormone-related risk factors in breast cancer differentially influence risk for disease subtypes classified by the status of the estrogen and progesterone receptors (ER/PR). However, it remains unclear whether human epidermal growth factor receptor 2 (HER2) or p53 expression status further differentiates these exposure-risk group associations. We evaluated the associations of oral contraceptive (OC) use and reproductive factors with incident invasive breast cancer subtypes among 1,197 population-based cases and 2,015 controls from the Los Angeles County or Detroit components of the Women's Contraceptive and Reproductive Experiences Study. Case-control comparisons by ER/PR/HER2/p53 status were conducted by multivariable polychotomous unconditional logistic regression methods. We found that OC use was not associated with any breast cancer subtype as defined by ER/PR/HER2/p53 status, except for a 2.9-fold increased risk of so-called triple-negative tumors (ER(-)/PR(-)/HER2(-)) among women of 45 to 64 years of age who started OC use before age 18. Parity was associated with a decreased risk of luminal A (ER(+) or PR(+), HER2(-)), luminal B (ER(+) or PR(+)/HER2(+)), and ER(-)/PR(-)/HER2(+) tumors. Age at first full-term pregnancy was positively associated with luminal A tumors among older women. Neither of these reproductive factors was associated with triple-negative tumors. Long duration of breast-feeding lowered the risk of triple-negative and luminal A tumors. p53 status did not define further differential risk patterns. Our findings offer evidence of differences in the hormone-related risk factors between triple-negative cancers and other ER/PR/HER2-defined subtypes of breast cancer.

Triple-negative breast cancer: molecular features, pathogenesis, treatment and current lines of research

Breast cancer is a heterogeneous disease with different morphologies, molecular profiles, clinical behaviour and response to therapy. The triple negative is a particular type of breast cancer defined by absence of oestrogen and progesterone receptor expression as well as absence of ERBB2 amplification. It is characterized by its biological aggressiveness, worse prognosis and lack of a therapeutic target in contrast with hormonal receptor positive and ERBB2+ breast cancers. Given these characteristics, triple-negative breast cancer is a challenge in today's clinical practice. A new breast cancer classification emerged recently in the scientific scene based in gene expression profiles. The new subgroups (luminal, ERBB2, normal breast and basal-like) have distinct gene expression patterns and phenotypical characteristics. Triple-negative breast cancer shares phenotypical features with basal-like breast cancer, which is in turn the most aggressive and with worse outcome. Since microarray gene-expression assays are only used in the research setting, clinicians use the triple-negative definition as a surrogate of basal-like breast cancer. The aim of this review, that focuses on triple-negative breast cancer, is to summarize the most relevant knowledge on this particular type of cancer in terms of molecular features, pathogenesis, clinical characteristics, current treatments and the new therapeutic options that include the use of platinum compounds, EGFR antagonists, antiangiogenics and PARP inhibitors. Advances in research are promising and new types of active drugs will become a reality in the near future, making possible a better outcome for this subgroup of breast cancer patients.

Epigenetic Reactivation of Estrogen Receptor: Promising Tools for Restoring Response to Endocrine Therapy

Breast tumors expressing estrogen receptor alpha (ER) respond well to therapeutic strategies using SERMs (selective estrogen receptor modulators) such as tamoxifen. However, about thirty percent of invasive breast cancers are hormone independent because they lack ER expression due to hypermethylation of ER promoter. Treatment of ER-negative breast cancer cells with demethylating agents and histone deacetylase inhibitors leads to expression of ER mRNA and functional protein. Additionally, growth factor signaling pathways have also been implicated in ER silencing in ER-negative tumor phenotype. Recently, important role of components of ubiquitin-proteasome pathway has been shown in mediating downregulation of ER. In this article, we will review various mechanisms underlying the silencing of ER in ER negative tumor phenotype and discuss diverse strategies to combat it. Ongoing studies may provide the mechanistic insight to design therapeutic strategies directed towards epigenetic and non-epigenetic mechanisms in the prevention or treatment of ER-negative breast cancer.

Breast cancer molecular subtypes in patients with locally advanced disease: impact on prognosis, patterns of recurrence, and response to therapy

Gene expression profiling has led to the discovery of 4 distinct molecular subtypes of breast cancer: luminal A, luminal B, basal like, and HER2 enriched. Investigation of these subtypes in women with breast cancer has given insight into the heterogeneous biology and outcomes in patients with locally advanced disease. These subtypes have been found to be predictors for survival, response to systemic therapy, and locoregional recurrence. This review discusses the biology of locally advanced breast cancer and the available data on how molecular subtype may provide information regarding response to treatment and prognosis of women with locally advanced breast cancer.

Triple-negative breast cancer--current status and future directions

Triple-negative breast cancer (TNBC) is defined by a lack of expression of both estrogen and progesterone receptor as well as human epidermal growth factor receptor 2. It is characterized by distinct molecular, histological and clinical features including a particularly unfavorable prognosis despite increased sensitivity to standard cytotoxic chemotherapy regimens. TNBC is highly though not completely concordant with various definitions of basal-like breast cancer (BLBC) defined by high-throughput gene expression analyses. The lack in complete concordance may in part be explained by both BLBC and TNBC comprising entities that in themselves are heterogeneous. Numerous efforts are currently being undertaken to improve prognosis for patients with TNBC. They comprise both optimization of choice and scheduling of common cytotoxic agents (i.e. addition of platinum salts or dose intensification strategies) and introduction of novel agents (i.e. poly-ADP-ribose-polymerase-1 inhibitors, agents targeting the epidermal growth factor receptor, multityrosine kinase inhibitors or antiangiogenic agents).

Obesity and angiolymphatic invasion in primary breast cancer

BACKGROUND

Obesity is associated with poorer breast cancer-specific survival. The purpose of this study was to investigate the relationships between obesity and the presence of angiolymphatic invasion as well as other features of invasive breast cancer, including stage at presentation, estrogen receptor (ER) status, triple-negative phenotype, and tumor grade.

METHODS

Detailed clinical and pathologic data were abstracted from the medical records of all 1,312 patients with stage I-III primary breast cancer who had breast surgery at the University of Michigan Comprehensive Cancer Center between January 1, 2000 and December 31, 2006. Bivariate and multivariate analyses were conducted to investigate the relationships between body mass index and tumor biologic features, controlling for menopausal status, diabetes and hypertension, hormone replacement therapy before diagnosis, race, and ethnicity.

RESULTS

In multivariate analyses, severe obesity was independently associated with the presence of angiolymphatic invasion [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.08-2.99, joint test of significance, P = 0.03]. Severe obesity was associated with lower likelihood of triple-negative breast cancer (OR 0.39, 95% CI 0.16-0.96). Among premenopausal women with diabetes, ER-negative (OR 5.22, 95% CI 1.12-24.29) and triple-negative (OR 14.8, 95% CI 1.92-113.91) disease was significantly more common.

DISCUSSION

In this large sample of invasive breast cancers, obesity was independently associated with the presence of angiolymphatic invasion. Higher rates of angiolymphatic invasion among obese women may account in part for poorer outcomes among obese women with breast cancer.

The association of metabolic syndrome with triple-negative breast cancer

Metabolic syndrome, a conglomerate of obesity, insulin resistance, dyslipidemia, and hypertension has been linked with an increased risk of breast cancer. We investigated the possible association of highly aggressive triple-negative breast cancer and the metabolic syndrome. Information on metabolic syndrome components and tumor characteristics were reviewed in a cohort of 176 patients (including 86 triple-negatives). Retrospective comparison was performed using Pearson Chi-square test or Student's t test for data analysis. A statistically significant association of triple-negative breast cancer with the metabolic syndrome was observed. In accordance with the NCEP (National Cholesterol Education Program) definition, 58.1% of triple-negative patients had metabolic syndrome compared to only 36.7% of non-triple-negative patients (P = 0.004). Consistently, by the AACE (American Association of Clinical Endocrinologists) criteria, 52.3% of triple-negative patients had metabolic syndrome as compared to 34.4% of non-triple-negative patients (P = 0.017). Blood glucose, triglyceride, and HDL levels but not hypertension or BMI (body mass index) showed significant independent association with triple-negative breast cancer. Additionally, triple-negative tumors displayed a significantly higher histological grade and relative paucity of ductal carcinoma in situ (DCIS) when compared to the non-triple-negative tumors (P < 0.001). Our study suggests that metabolic syndrome is significantly more prevalent in triple-negative breast cancer patients as opposed to non-triple-negative patients. Furthermore, triple-negative breast cancer showed a significantly higher histological grade and a relative absence of DCIS. Whether the presence of metabolic syndrome preferentially increases the risk of developing triple-negative-breast cancer remains to be elucidated with future prospective studies.

An admixture scan in 1,484 African American women with breast cancer

African American women with breast cancer present more commonly with aggressive tumors that do not express the estrogen receptor (ER) and progesterone receptor (PR) compared with European American women. Whether this disparity is the result of inherited factors has not been established. We did an admixture-based genome-wide scan to search for risk alleles for breast cancer that are highly differentiated in frequency between African American and European American women, and may contribute to specific breast cancer phenotypes, such as ER-negative (ER-) disease. African American women with invasive breast cancer (n = 1,484) were pooled from six population-based studies and typed at approximately 1,500 ancestry-informative markers. We investigated global genetic ancestry and did a whole genome admixture scan searching for breast cancer-predisposing loci in association with disease phenotypes. We found a significant difference in ancestry between ER+PR+ and ER-PR- women, with higher European ancestry among ER+PR+ individuals, after controlling for possible confounders (odds ratios for a 0 to 1 change in European ancestry proportion, 2.84; 95% confidence interval, 1.13-7.14; P = 0.026). Women with localized tumors had higher European ancestry than women with non-localized tumors (odds ratios, 2.65; 95% confidence interval, 1.11-6.35; P = 0.029). No genome-wide statistically significant associations were observed between European or African ancestry at any specific locus and breast cancer, or in analyses stratified by ER/PR status, stage, or grade. In summary, in African American women, genetic ancestry is associated with ER/PR status and disease stage. However, we found little evidence that genetic ancestry at any one region contributes significantly to breast cancer risk or hormone receptor status.

A polymorphic variant in human MDM4 associates with accelerated age of onset of estrogen receptor negative breast cancer

Murine double minute 4 (MDM4) shares significant structural homology with murine double minute 2 (MDM2) and interacts and regulates transcriptional activity of the tumor suppressor p53. In tumors with wild-type p53, there is often overexpression of MDM2 or MDM4 leading to functional inactivation of p53. A single-nucleotide polymorphism (SNP) in the promoter of human MDM2 (SNP309) was shown to associate with increased MDM2 expression and increased risk of cancer. This study evaluated the association of a SNP in human MDM4 (C>T) with age of onset of breast cancer in two independent cohorts. In cohort 1 of 675 patients, the average age of diagnosis for women with estrogen receptor (ER)-positive and ER-negative breast cancers was 53.2 and 48 years, respectively. In this cohort, homozygous variant (TT) carriers developed ER-negative carcinomas at an earlier age than homozygous wild-type (CC) or heterozygous (TC) such that the age at diagnosis was accelerated by 5.0 years (P = 0.018). This association was validated in a second cohort of breast cancer patients (n = 148), where TT carriers with ER-negative cancer developed the disease 3.8 years earlier than CC carriers (P = 0.006). The effect was more pronounced in Caucasians with ER-negative ductal carcinomas with TT homozygotes developing disease 7.5 years (P = 0.031) and 6.2 years (P = 7 x 10(-5)) earlier than CC carriers in cohorts 1 and 2, respectively. No association was seen in ER-positive ductal cancers suggesting that the SNP in MDM4 only has a functional association in ER-negative breast cancer.

Population differences in breast cancer: survey in indigenous African women reveals over-representation of triple-negative breast cancer

PURPOSE

Compared with white women, black women experience a disproportionate burden of aggressive breast cancer for reasons that remain unknown and understudied. In the first study of its kind, we determined the distribution of molecular subtypes of invasive breast tumors in indigenous black women in West Africa.

PATIENTS AND METHODS

The study comprised 507 patients diagnosed with breast cancer between 1996 and 2007 at six geographic regions in Nigeria and Senegal. Formalin-fixed and paraffin-embedded sections were constructed into tissue microarrays and immunostained with 15 antibodies. Five molecular subtypes were determined, and hierarchical cluster analysis was conducted to explore subgroups for unclassified cases.

RESULTS

The mean (+/- standard deviation) age of 378 patients in the first cohort was 44.8 +/- 11.8 years, with the majority of women presenting with large (4.4 +/- 2.0 cm) high-grade tumors (83%) in advanced stages (72% node positive). The proportions of estrogen receptor (ER) -positive, progesterone receptor-positive, and human epidermal growth factor receptor 2 (HER2) -positive tumors were 24%, 20%, and 17%, respectively. Triple negativity for these markers was predominant, including basal-like (27%) and unclassified subtype (28%). Other subtypes were luminal A (27%), luminal B (2%), and HER2 positive/ER negative (15%). The findings were replicated in the second cohort of 129 patients. The unclassified cases could be grouped into a bad prognosis branch, with expression of vascular endothelial growth factor, B-cell lymphoma extra-large protein, and Cyclin E, and a good prognosis branch, with expression of B-cell lymphoma protein 2 and Cyclin D1.

CONCLUSION

These findings underscore the urgent need for research into the etiology and treatment of the aggressive molecular subtypes that disproportionately affect young women in the African diaspora.

Vasomotor symptoms, adoption of a low-fat dietary pattern, and risk of invasive breast cancer: a secondary analysis of the Women's Health Initiative randomized controlled dietary modification trial

PURPOSE

To assess whether the effect of a low-fat dietary pattern on breast cancer incidence varied by report of baseline vasomotor symptoms.

METHODS

Postmenopausal women age 50 to 79 years enrolled onto the Women's Health Initiative (WHI) Dietary Modification trial from 1993 to 1998 were randomly assigned to a low-fat dietary intervention (n = 19,541) or comparison (n = 29,294). Presence of vasomotor symptoms at baseline was ascertained from a 34-item self-report symptom inventory. Women were queried semi-annually for a new diagnosis of breast cancer. Each case report was verified by medical record and pathology report review by centrally trained WHI physician adjudicators.

RESULTS

Among participants who reported hot flashes (HFs) at baseline (n = 3,375), those assigned to the low-fat diet had a breast cancer rate of 0.27 compared with their counterparts in the control group who had a rate of 0.41 (hazard ratio [HR] = 0.65; 95% CI, 0.42 to 1.01). Among women reporting no HFs (n = 45,160), the breast cancer rate was 0.42 in those assigned to the low-fat diet compared with 0.46 in the control group (HR = 0.93; 95% CI, 0.84 to 1.03; P for interaction = .12 by HF status). Furthermore, the dietary benefits observed seemed to be specific to estrogen receptor (ER) -positive/progesterone receptor (PR) -positive tumors (ER positive/PR positive v other, P for risk = .03). Although women with and without HFs differed with regard to breast cancer risk factors, the effect of the diet intervention on breast cancer incidence by HF status was consistent across risk factor strata.

CONCLUSION

The results of this trial, which are hypothesis generating, suggest that HFs may identify a subgroup of postmenopausal women whose risk of invasive breast cancer might be reduced with the adoption of a low-fat eating pattern.

Challenges in studying the etiology of breast cancer subtypes

Research that classifies breast tumors into homogenous subgroups could ultimately help to define public health prevention strategies for aggressive breast cancer subtypes. However, etiologic research on molecular breast cancer subtypes must overcome several challenges. Stratifying breast cancers into subgroups can reduce statistical power and, therefore, may require non-traditional analytical methods. Integrating results across studies is hampered by varying definitions of molecular subtypes, with some studies using triple negative status and others using specific markers to define basal-like cancers. In addition, triple negative and basal-like breast cancers appear to show strong associations with race, so the varied racial and ethnic composition of different datasets can make comparison across studies challenging. In spite of these challenges, some strong and consistent associations between triple negative or basal-like breast cancer and demographic variables are emerging, and there are hints that prevention strategies for this aggressive subtype of breast cancer may also be attainable.

Biology, metastatic patterns, and treatment of patients with triple-negative breast cancer

Of the estimated 1 million cases of breast cancer diagnosed annually worldwide, it is estimated that over 170,000 will harbor the triple-negative (estrogen receptor/progesterone receptor/HER2-negative) phenotype. Most, though not all, triple-negative breast cancers will be basal-like on gene expression micorarrays. The basal-like molecular subtype exhibits a unique molecular profile and set of risk factors, aggressive and early pattern of metastasis, limited treatment options, and poor prognosis. Large population-based studies have identified a higher proportion of triple-negative breast tumors among premenopausal African American women, and a suggestion that increased parity, younger age at first-term pregnancy, shorter duration of breast feeding, and elevated hip-to-waist ratio might be particular risk factors. When BRCA1 mutation carriers develop breast cancer, it is usually basal-like; given the central role of BRCA1 in DNA repair, this could have profound therapeutic implications. When diagnosed, triple-negative breast cancers illustrate preferential relapse in visceral organs, including the central nervous system. Although initial response to chemotherapy might be more profound, relapse is early and common among triple-negative breast cancers compared with luminal breast cancers. The armamentarium of "targeted therapeutics" for triple-negative breast cancer is evolving and includes strategies to inhibit angiogenesis, epidermal growth factor receptor, and other kinases. Finally, the positive association between triple-negative breast cancer and BRCA mutations makes inhibition of poly(adenosine diphosphate-ribose) polymerase-1 an attractive therapeutic strategy that is in active study.

Epidemiology of breast cancer subtypes in two prospective cohort studies of breast cancer survivors

Introduction

The aim of this study was to describe breast tumor subtypes by common breast cancer risk factors and to determine correlates of subtypes using baseline data from two pooled prospective breast cancer studies within a large health maintenance organization.

Methods

Tumor data on 2544 invasive breast cancer cases subtyped by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (Her2) status were obtained (1868 luminal A tumors, 294 luminal B tumors, 288 triple-negative tumors and 94 Her2-overexpressing tumors). Demographic, reproductive and lifestyle information was collected either in person or by mailed questionnaires. Case-only odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression, adjusting for age at diagnosis, race/ethnicity, and study origin.

Results

Compared with luminal A cases, luminal B cases were more likely to be younger at diagnosis (P = 0.0001) and were less likely to consume alcohol (OR = 0.74, 95% CI = 0.56 to 0.98), use hormone replacement therapy (HRT) (OR = 0.66, 95% CI = 0.46 to 0.94), and oral contraceptives (OR = 0.73, 95% CI = 0.55 to 0.96). Compared with luminal A cases, triple-negative cases tended to be younger at diagnosis (P ≤ 0.0001) and African American (OR = 3.14, 95% CI = 2.12 to 4.16), were more likely to have not breastfed if they had parity greater than or equal to three (OR = 1.68, 95% CI = 1.00 to 2.81), and were more likely to be overweight (OR = 1.82, 95% CI = 1.03 to 3.24) or obese (OR = 1.97, 95% CI = 1.03 to 3.77) if premenopausal. Her2-overexpressing cases were more likely to be younger at diagnosis (P = 0.03) and Hispanic (OR = 2.19, 95% CI = 1.16 to 4.13) or Asian (OR = 2.02, 95% CI = 1.05 to 3.88), and less likely to use HRT (OR = 0.45, 95% CI = 0.26 to 0.79).

Conclusions

These observations suggest that investigators should consider tumor heterogeneity in associations with traditional breast cancer risk factors. Important modifiable lifestyle factors that may be related to the development of a specific tumor subtype, but not all subtypes, include obesity, breastfeeding, and alcohol consumption. Future work that will further categorize triple-negative cases into basal and non-basal tumors may help to elucidate these associations further.

The epidemiology of triple-negative breast cancer, including race

OBJECTIVE

Predictors of intrinsic breast cancer subtypes, including the triple-negative (TN) subtype, are largely unknown. We evaluated whether anthropometrics, demographics, and reproductive history were associated with distinct breast cancer subtypes.

METHODS

Invasive breast tumors from a population-based case-control study of 476 (116 black and 360 white) Atlanta women aged 20-54, diagnosed between 1990 and 1992, were centrally reviewed and immunohistochemically analyzed for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2); then grouped [TN (ER-PR-HER2-); ER-PR-HER2+; ER/PR+HER2+; ER/PR+HER2- (case-only reference group)]. Data were from interviews and anthropometric measurements; adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression, including both case-only and case-control comparisons.

RESULTS

From the case-only analyses and compared with the ER/PR+HER2- subtype, women with TN tumors were more likely to be obese than normal/underweight [OR = 1.89 (95% CI = 1.22, 2.92)]. Regardless of HER2 status, ER-PR- tumors were associated with black race, young age at first birth, having a recent birth, and being overweight.

CONCLUSIONS

Distinct breast cancer subtypes have unique sociodemographic, anthropometric and reproductive characteristics and possibly different pathways for development.

Risk factors for triple-negative breast cancer in women under the age of 45 years

Little is known about the etiologic profile of triple-negative breast cancer (negative for estrogen receptor/progesterone receptor/human epidermal growth factor), a breast cancer subtype associated with high mortality and inadequate therapeutic options. We undertook this study to assess the risk for triple-negative breast cancer among women 45 years of age and younger in relation to demographic/lifestyle factors, reproductive history, and oral contraceptive use. Study participants were ascertained in two previous population-based, case-control studies. Eligible cases included all primary invasive breast cancers among women ages 20 to 45 years in the Seattle-Puget Sound area, diagnosed between January 1983 and December 1992, for whom complete data was obtained for estrogen receptor, progesterone receptor, and human epidermal growth factor status (n = 897; including n = 187 triple-negative breast cancer cases). Controls were age matched and ascertained via random digit dialing. Oral contraceptive use > or =1 year was associated with a 2.5-fold increased risk for triple-negative breast cancer (95% confidence interval, 1.4-4.3) and no significantly increased risk for non-triple-negative breast cancer (P(heterogeneity) = 0.008). Furthermore, the risk among oral contraceptive users conferred by longer oral contraceptive duration and by more recent use was significantly greater for triple-negative breast cancer than non-triple-negative breast cancer (P(heterogeneity) = 0.02 and 0.01, respectively). Among women < or =40 years, the relative risk for triple-negative breast cancer associated with oral contraceptive use > or =1 year was 4.2 (95% confidence interval, 1.9-9.3), whereas there was no significantly increased risk with oral contraceptive use for non-triple-negative breast cancer among women < or =40 years, nor for triple-negative breast cancer or non-triple-negative breast cancer among women 41 to 45 years of age. In conclusion, significant heterogeneity exists for the association of oral contraceptive use and breast cancer risk between triple-negative breast cancer and non-triple-negative breast cancer among young women, lending support to a distinct etiology.

Triple-negative breast cancers are increased in black women regardless of age or body mass index

Introduction

We investigated clinical and pathologic features of breast cancers (BC) in an unselected series of patients diagnosed in a tertiary care hospital serving a diverse population. We focused on triple-negative (Tneg) tumours (oestrogen receptor (ER), progesterone receptor (PR) and HER2 negative), which are associated with poor prognosis.

Methods

We identified female patients with invasive BC diagnosed between 1998 and 2006, with data available on tumor grade, stage, ER, PR and HER2 status, and patient age, body mass index (BMI) and self-identified racial/ethnic group. We determined associations between patient and tumour characteristics using contingency tables and multivariate logistic regression.

Results

415 cases were identified. Patients were racially and ethnically diverse (born in 44 countries, 36% white, 43% black, 10% Hispanic and 11% other). 47% were obese (BMI > 30 kg/m2). 72% of tumours were ER+ and/or PR+, 20% were Tneg and 13% were HER2+. The odds of having a Tneg tumour were 3-fold higher (95% CI 1.6, 5.5; p = 0.0001) in black compared with white women. Tneg tumours were equally common in black women diagnosed before and after age 50 (31% vs 29%; p = NS), and who were obese and non-obese (29% vs 31%; p = NS). Considering all patients, as BMI increased, the proportion of Tneg tumours decreased (p = 0.08).

Conclusions

Black women of diverse background have 3-fold more Tneg tumours than non-black women, regardless of age and BMI. Other factors must determine tumour subtype. The higher prevalence of Tneg tumours in black women in all age and weight categories likely contributes to black women's unfavorable breast cancer prognosis.

"New" molecular taxonomy in breast cancer

Advances in the analysis of expression profiles, using genomic techniques, have revealed the high heterogeneity present in breast cancers. These approaches have served to identify different breast cancer subgroups with specific molecular characteristics that could sub-classify these tumours as carcinomas expressing hormone receptors, denominated Luminal subtype, and tumours with negative expression of hormone receptors, the Basal and HER2+ phenotypes. Therefore, during recent years, identification of markers characteristic of each subtype has been the focus of many research groups. All of these breast tumour subtypes probably have specific clinical and morphological features; however, this hypothesis needs to be confirmed by analysing more homogenous series. Although this "new" classification has limitations, it could be useful in the clinical practice, allowing not only a more accurate prognosis in breast cancer patients but also a selective treatment for each predefined subtype.

Coding polymorphisms in Casp5, Casp8 and DR4 genes may play a role in predisposition to lung cancer

Apoptosis plays a role in the elimination of DNA-damaged cells thus protecting the host from cancer development. Some data indicate that normal variations within the sequence of apoptotic genes may lead to suboptimal apoptotic capacity and therefore increased cancer risk. We tested 19 coding apoptotic gene SNPs in 2-stage molecular epidemiological study. For the preliminary sorting of SNP candidates, we employed a "comparison of extremes" approach, where 111 patients with highly pronounced LC susceptibility (non-smokers or young-onset light smokers) were analyzed against 110 subjects with the evidence for LC tolerance (elderly tumor-free heavy smokers). Three genotypes demonstrated possible association with LC risk (Leu/Leu-homozygotes for Casp5 Val318Leu versus other genotypes: OR=2.47 (95% CI: 1.07-5.69), p=0.03; His-carriers for Casp8 His302Asp: OR=2.26 (95% CI: 1.18-4.31), p=0.02; Arg-carriers for DR4 Lys441Arg: OR=1.89 (95% CI: 1.05-3.40), p=0.03), and therefore were selected for the validation. The extended study included 2 case-control series, namely subjects from Russia (351 LC cases and 538 controls) and Moldova (296 LC cases and 295 controls). Interestingly, all three candidate genotypes consistently demonstrated OR above 1 both in Russian and in Moldovian groups. Although the combined Mantel-Haenszel analysis yet failed to reach statistical significance (OR=1.22 (95% CI: 0.90-1.65), p=0.21; OR=1.17 (95% CI: 0.92-1.50), p=0.21; OR=1.19 (95% CI: 0.95-1.51), p=0.14, respectively), the obtained data indicate that Casp5, Casp8 and DR4 gene polymorphisms may deserve consideration in large-scale case-control studies of LC risk modifiers.

Is there a difference in the association between percent mammographic density and subtypes of breast cancer? Luminal A and triple-negative breast cancer

BACKGROUND

Mammographic density is a potentially modifiable risk factor for breast cancer. To what extent mammographic density is a predictor for both hormone receptor-positive and hormone receptor-negative tumors is unclear. Even less is known about whether mammographic density predicts subtypes of breast cancer defined by expression status of the three receptors: estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2).

METHODS

We estimated the association of percent mammographic density with subtypes of invasive breast cancer among 479 population-based female breast cancer patients and 376 control subjects ages 35 to 64 years. The expression status of ER, PR, and HER-2 was assessed using immunohistochemistry methods in a single laboratory. We considered ER+ or PR+ plus HER-2- tumors as luminal A breast cancer and ER-/PR-/HER-2- tumors as triple-negative breast cancer. We used unconditional logistic regression methods to estimate odd ratios (95% confidence intervals) for both case-control and case-case comparisons.

RESULTS

Mammographic density was associated with increased risk of both invasive breast cancer subtypes, luminal A and triple-negative, in the case-control analysis. Results from case-case comparisons yielded no differences between the two subtypes among all women combined or in analyses done separately by race (White versus African American women) or menopausal status (premenopausal versus postmenopausal women; all P values > 0.05).

CONCLUSIONS

Our results suggest that percent mammographic density is positively associated with both luminal A and triple-negative breast cancer.

Triple-negative breast cancer: risk factors to potential targets

Triple-negative breast cancer has recently been recognized as an important subgroup of breast cancer with a distinct outcome and therapeutic approach when compared with other subgroups of breast cancer. Triple-negative breast cancer comprises primarily, but not exclusively, a molecularly distinct subtype of breast cancer, the basal-like subtype. We do not yet have an assay to identify basal-like breast cancer in clinical samples, so triple-negative breast cancer has become a commonly used proxy for this subtype. The molecular biology and pathophysiology of triple-negative breast cancer are not completely understood, but understanding is improving rapidly with the advent of sophisticated molecular biology platforms. Moreover, the established risk factors of breast cancer as a whole may not apply to this unique subgroup of patients. Finally, because triple-negative breast cancer is defined by the absence of a target, there are currently limitations to using a tailored therapeutic approach, leaving conventional cytotoxic therapies as the mainstay. Active preclinical and clinical research programs focus on defining the clinical behavior, delineating the risk factors, and more completely understanding the molecular biology of triple-negative breast cancer to improve prevention, optimize conventional agents, and unveil novel therapeutic targets. This CCR focus article will review the current state of the art on triple-negative breast cancer.

Advances in breast cancer: pathways to personalized medicine

Breast cancer is a complex disease caused by the progressive accumulation of multiple gene mutations combined with epigenetic dysregulation of critical genes and protein pathways. There is substantial interindividual variability in both the age at diagnosis and phenotypic expression of the disease. With an estimated 1,152,161 new breast cancer cases diagnosed worldwide per year, cancer control efforts in the postgenome era should be focused at both population and individual levels to develop novel risk assessment and treatment strategies that will further reduce the morbidity and mortality associated with the disease. The discovery that mutations in the BRCA1 and BRCA2 genes increase the risk of breast and ovarian cancers has radically transformed our understanding of the genetic basis of breast cancer, leading to improved management of high-risk women. A better understanding of tumor host biology has led to improvements in the multidisciplinary management of breast cancer, and traditional pathologic evaluation is being complemented by more sophisticated genomic approaches. A number of genomic biomarkers have been developed for clinical use, and increasingly, pharmacogenetic end points are being incorporated into clinical trial design. For women diagnosed with breast cancer, prognostic or predictive information is most useful when coupled with targeted therapeutic approaches, very few of which exist for women with triple-negative breast cancer or those with tumors resistant to chemotherapy. The immediate challenge is to learn how to use the molecular characteristics of an individual and their tumor to improve detection and treatment, and ultimately to prevent the development of breast cancer. The five articles in this edition of CCR Focus highlight recent advances and future directions on the pathway to individualized approaches for the early detection, treatment, and prevention of breast cancer.

Genetic susceptibility loci for breast cancer by estrogen receptor status

Breast cancer is a heterogeneous disease, and risk factors could be differentially associated with the development of distinct tumor subtypes that manifest different biological behavior and progression. In support of this view, there is growing evidence that known breast cancer risk factors vary by hormone receptor status and perhaps other pathologic characteristics of disease. Recent work from large consortial studies has led to the discovery of novel breast cancer susceptibility loci in genic (CASP8, FGFR2, TNRC9, MAP3K1, LSP1) and nongenic regions (8q24, 2q35, 5p12) of the genome, and to the finding of substantial heterogeneity by tumor characteristics. In particular, susceptibility loci in FGFR2, TNRC9, 8q24, 2q35, and 5p12 have stronger associations for estrogen receptor-positive (ER+) disease than estrogen receptor-negative (ER -) disease. These findings suggest that common genetic variants can influence the pathologic subtype of breast cancer, and provide further support for the hypothesis that ER+ and ER(-) disease result from different etiologic pathways. Current studies had limited power to detect susceptibility loci for less common tumor subtypes, such as ER(-) disease including triple-negative and basal-like tumors. Ongoing work targeting uncommon subtypes is likely to identify additional tumor-specific susceptibility loci in the near future. Characterization of etiologic heterogeneity of breast cancer may lead to improvements in the understanding of the biological mechanisms for breast cancer, and ultimately result in improvements in prevention, early detection, and treatment.

Age-related crossover in breast cancer incidence rates between black and white ethnic groups

BACKGROUND

Although breast cancer incidence is higher in black women than in white women among women younger than 40 years, the reverse is true among those aged 40 years or older. This crossover in incidence rates between black and white ethnic groups has been well described, has not been completely understood, and has been viewed as an artifact.

METHODS

To quantify this incidence rate crossover, we examined data for 440 653 women with invasive breast cancer from the National Cancer Institute's Surveillance, Epidemiology, and End Results database from January 1, 1975, through December 31, 2004. Data on invasive female breast cancers were stratified by race, age at diagnosis, year of diagnosis, and tumor characteristics. Standard descriptive analyses were supplemented with Poisson regression models, age-period-cohort models, and two-component mixture models. All statistical tests were two-sided.

RESULTS

We observed qualitative (ie, crossing or reversing) interactions between age and race. That is, age-specific incidence rates overall (expressed as number of breast cancers per 100 000 woman-years) were higher among black women (15.5) than among white women (13.1) younger than 40 years (difference = 2.4, 95% confidence interval [CI] = 2.4 to 2.4), and then, age-specific rates crossed with rates higher among white women (281.3) than among black women (239.5) aged 40 years or older (difference = 41.8, 95% CI = 41.7 to 41.9). The black-to-white incidence rate crossover was observed for all tumor characteristics assessed, although the crossover occurred at earlier ages of diagnosis for low-risk tumor characteristics than for high-risk tumor characteristics. The incidence rate crossover between ethnic groups was robust (ie, reliable and reproducible) to adjustment for calendar period and birth cohort effects in age-period-cohort models (P < .001 for difference by race).

CONCLUSION

Although this ecologic study cannot determine the individual-level factors responsible for the racial crossover in vital rates, it confirms that the age-related crossover in breast cancer incidence rates between black and white ethnic groups is a robust age-specific effect that is independent of period and cohort effects.

Breast cancer classification according to immunohistochemical markers: clinicopathologic features and short-term survival analysis in a population-based study from the South of Switzerland

BACKGROUND

Breast cancer may be classified into distinct molecular subtypes based on gene expression profiling and/or immunophenotypic characteristics. Aim of the study was to investigate prevalence, clinicopathologic features and overall survival (OS) of molecular subtypes, in a large European population-based study.

PATIENTS AND METHODS

All invasive breast cancers from 2003 to 2007 were selected from the files of Ticino Cancer Registry. Molecular subtypes were defined by immunohistochemical markers. Clinicopathological characteristics and short-term OS were analyzed.

RESULTS

Of 1214 invasive breast cancers, 73.2% were luminal A subtype, 13.8% luminal B, 7.4% basal like and 5.6% Her2/neu. Basal like presented largely in premenopausal women and displayed aggressive features, such as large tumor size, poorly differentiated cancers, high Ki-67 proliferation index and the worst 24-month OS. Luminal A included the highest percentage of patients >70, the highest proportion of stage I tumors and well/moderately differentiated lesions. Her2/neu was more frequent in postmenopausal women and showed the highest percentage of positive lymph nodes and stage IV cases.

CONCLUSION

This is a comprehensive European population-based study on breast cancer molecular subtypes. We provide strong evidence that the molecular classification is useful for clinical management and superior to World Health Organization classification in terms of short-term prognostic value.

In vitro and in vivo analysis of B-Myb in basal-like breast cancer

A defining feature of basal-like breast cancer, a breast cancer subtype with poor clinical prognosis, is the high expression of 'proliferation signature' genes. We identified B-Myb, a MYB family transcription factor that is often amplified and overexpressed in many tumor types, as being highly expressed in the proliferation signature. However, the roles of B-Myb in disease progression, and its mammary-specific transcriptional targets, are poorly understood. Here, we showed that B-Myb expression is a significant predictor of survival and pathological complete response to neoadjuvant chemotherapy in breast cancer patients. We also identified a significant association between the G/G genotype of a nonsynonymous B-Myb germline variant (rs2070235, S427G) and an increased risk of basal-like breast cancer [OR 2.0, 95% CI (1.1-3.8)]. In immortalized, human mammary epithelial cell lines, but not in basal-like tumor lines, cells ectopically expressing wild-type B-Myb or the S427G variant showed increased sensitivity to two DNA topoisomerase IIalpha inhibitors, but not to other chemotherapeutics. In addition, microarray analyses identified many G2/M genes as being induced in B-Myb overexpressing cells. These results confirm that B-Myb is involved in cell cycle control, and that its dysregulation may contribute to increased sensitivity to a specific class of chemotherapeutic agents. These data provide insight into the influence of B-Myb in human breast cancer, which is of potential clinical importance for determining disease risk and for guiding treatment.

Recent trends in breast cancer among younger women in the United States

Increases in the incidence of postmenopausal breast cancers have been linked to screening and menopausal hormone use, but younger women have received less attention. Thus, we analyzed trends in breast cancer incidence (N = 387 231) using the National Cancer Institute's Surveillance, Epidemiology, and End Results Program 13-Registry database (1992-2004). Whites had higher incidence rates than blacks after age 40 years, but the reverse was true among younger women (black-white crossover). Among younger women, the rate per 100,000 woman-years was 16.8 for black vs 15.1 for white women; the highest black-white incidence rate ratio (IRR) was seen among women younger than 30 years (IRR = 1.52, 95% confidence interval = 1.34 to 1.73). This risk pattern was not observed in other ethnic groups. The black-white crossover among younger women was largely restricted to breast cancers with favorable tumor characteristics. The annual percentage change in the incidence of invasive breast cancers decreased modestly among older women but increased among younger (<40 years) white women. Continued surveillance of trends is needed, particularly for molecular subtypes that preferentially occur among young women.

Reproductive and hormonal risk factors for postmenopausal luminal, HER-2-overexpressing, and triple-negative breast cancer

BACKGROUND

Molecular profiling studies have identified subtypes of breast cancer that can be approximately classified by estrogen receptor (ER), progesterone receptor (PR), and HER-2/neu (HER-2) expression. These molecular subtypes are prognostically significant, but to the authors' knowledge, differences in their etiologic profiles have not been established. Reproductive factors may plausibly be differentially correlated with the risk of different breast cancer subtypes because these factors are presumed to impact exposure to endogenous sex hormones.

METHODS

The authors pooled 2 population-based, case-control studies of breast cancer in women ages 55 to 79 years for an analysis including 1476 controls and 1023 cases of luminal breast cancer, 39 cases of HER-2-overexpressing breast cancer, and 78 cases of triple-negative breast cancer. Polytomous logistic regression was used to compare each case group with controls.

RESULTS

Associations varied by molecular subtype. Early age at menarche was only found to be associated with risk of HER-2-overexpressing disease (odds ratio [OR] of 2.7; 95% confidence interval [95% CI], 1.4-5.5), whereas breastfeeding for > or =6 months was only found to be protective for luminal and triple-negative disease (OR of 0.8 [95% CI, 0.6-1.0] and OR of 0.5 [95% CI, 0.3-0.9], respectively). Both late age at menopause and the use of estrogen plus progestin hormone therapy were only found to be associated with risk of luminal disease (OR of 1.6 [95% CI, 1.1-2.2] and OR of 1.7 [95% CI, 1.3-2.1], respectively). No differences in risks associated with parity or age at first live birth were observed by subtype.

CONCLUSIONS

Certain reproductive factors may have a greater impact on the risk of certain molecular subtypes of disease compared with others. Future studies that further define the etiology of breast cancer subtypes will add to the biologic understanding of this disease.

Understanding and treating triple-negative breast cancer

Triple-negative breast cancer is a subtype of breast cancer that is clinically negative for expression of estrogen and progesterone receptors (ER/PR) and HER2 protein. It is characterized by its unique molecular profile, aggressive behavior, distinct patterns of metastasis, and lack of targeted therapies. Although not synonymous, the majority of triple-negative breast cancers carry the "basal-like" molecular profile on gene expression arrays. The majority of BRCA1-associated breast cancers are triple-negative and basal-like; the extent to which the BRCA1 pathway contributes to the behavior of sporadic basal-like breast cancers is an area of active research. Epidemiologic studies illustrate a high prevalence of triple-negative breast cancers among younger women and those of African descent. Increasing evidence suggests that the risk factor profile differs between this subtype and the more common luminal subtypes. Although sensitive to chemotherapy, early relapse is common and a predilection for visceral metastasis, including brain metastasis, is seen. Targeted agents, including epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), and poly (ADP-ribose) polymerase (PARP) inhibitors, are currently in clinical trials and hold promise in the treatment of this aggressive disease.

The removal of multiplicative, systematic bias allows integration of breast cancer gene expression datasets - improving meta-analysis and prediction of prognosis

Background

The number of gene expression studies in the public domain is rapidly increasing, representing a highly valuable resource. However, dataset-specific bias precludes meta-analysis at the raw transcript level, even when the RNA is from comparable sources and has been processed on the same microarray platform using similar protocols. Here, we demonstrate, using Affymetrix data, that much of this bias can be removed, allowing multiple datasets to be legitimately combined for meaningful meta-analyses.

Results

A series of validation datasets comparing breast cancer and normal breast cell lines (MCF7 and MCF10A) were generated to examine the variability between datasets generated using different amounts of starting RNA, alternative protocols, different generations of Affymetrix GeneChip or scanning hardware. We demonstrate that systematic, multiplicative biases are introduced at the RNA, hybridization and image-capture stages of a microarray experiment. Simple batch mean-centering was found to significantly reduce the level of inter-experimental variation, allowing raw transcript levels to be compared across datasets with confidence. By accounting for dataset-specific bias, we were able to assemble the largest gene expression dataset of primary breast tumours to-date (1107), from six previously published studies. Using this meta-dataset, we demonstrate that combining greater numbers of datasets or tumours leads to a greater overlap in differentially expressed genes and more accurate prognostic predictions. However, this is highly dependent upon the composition of the datasets and patient characteristics.

Conclusion

Multiplicative, systematic biases are introduced at many stages of microarray experiments. When these are reconciled, raw data can be directly integrated from different gene expression datasets leading to new biological findings with increased statistical power.

High prevalence of triple-negative tumors in an urban cancer center

BACKGROUND

A disparate proportion of breast cancer deaths occur among young women, those of African-American (AA) ancestry, and particularly young AA women. Estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor-2 (HER-2) are key clinically informative biomarkers. The triple-negative (ER-/PR-/HER-2-) tumor subgroup is intrinsically resistant to treatment and portends a poor prognosis. Age, race, and socioeconomic status have been associated with triple-negative tumors (TNT). In the current study, the authors investigated breast cancer subgroups among patients in an urban cancer center serving a multiracial, low socioeconomic population.

METHODS

This case series analyzed female invasive breast cancers diagnosed and/or treated between 2003 and 2004 in the AVON Comprehensive Breast Center at Grady Hospital in Atlanta, Georgia. Data were obtained from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program, and augmented by the hospital registry and pathology reports. Statistical analyses utilized frequency distributions and logistic regression.

RESULTS

Of 190 breast cancers; 167 (88%) were diagnosed among AA and 23 (12%) were diagnosed among non-AA women. The median age at diagnosis in the 2 groups was 58 years and 57 years, respectively. TNT prevalence was found to differ by race (29.3% among AA women and 13.0% among non-AA women; P = .010). Differences persisted after adjustment for age and stage (odds ratio [OR] of 3.1; 95%confidence interval [95% CI], 0.8-11.6). The majority of recurrences (40.0%) occurred among women with TNT, who were also most likely to experience a fatal event (OR of 3.7; 95%CI, 1.1-13.0).

CONCLUSIONS

Despite a similarity in their age at diagnosis, AA women in our urban cancer center presented with a higher prevalence of TNT and TNT was found to predict the poorest outcomes. Institutional interactive breast conferences and intervention/navigation programs could help to dispel breast cancer disparities and improve outcomes.

Comparison of molecular phenotypes of ductal carcinoma in situ and invasive breast cancer

INTRODUCTION

At least four major categories of invasive breast cancer that are associated with different clinical outcomes have been identified by gene expression profiling: luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) and basal-like. However, the prevalence of these phenotypes among cases of ductal carcinoma in situ (DCIS) has not been previously evaluated in detail. The purpose of this study was to compare the prevalence of these distinct molecular subtypes among cases of DCIS and invasive breast cancer.

METHODS

We constructed tissue microarrays (TMAs) from breast cancers that developed in 2897 women enrolled in the Nurses' Health Study (1976 to 1996). TMA slides were immunostained for oestrogen receptor (ER), progesterone receptor (PR), HER2, cytokeratin 5/6 (CK5/6) and epidermal growth factor receptor (EGFR). Using these immunostain results, cases were grouped into molecularly defined subtypes.

RESULTS

The prevalence of the distinct molecular phenotypes differed significantly between DCIS (n = 272) and invasive breast cancers (n = 2249). The luminal A phenotype was significantly more frequent among invasive cancers (73.4%) than among DCIS lesions (62.5%) (p = 0.0002). In contrast, luminal B and HER2 molecular phenotypes were both more frequent among DCIS (13.2% and 13.6%, respectively) as compared with invasive tumours (5.2% and 5.7%, respectively) (p < 0.0001). The basal-like phenotype was more frequent among the invasive cancers (10.9%) than DCIS (7.7%), although this difference was not statistically significant (p = 0.15). High-grade DCIS and invasive tumours were more likely to be HER2 type and basal-like than low- or intermediate-grade lesions. Among invasive tumours, basal-like and HER2 type tumours were more likely to be more than 2 cm in size, high-grade and have nodal involvement compared with luminal A tumours.

CONCLUSION

The major molecular phenotypes previously identified among invasive breast cancers were also identified among cases of DCIS. However, the prevalence of the luminal A, luminal B and HER2 phenotypes differed significantly between DCIS and invasive breast cancers.

Body size and risk of luminal, HER2-overexpressing, and triple-negative breast cancer in postmenopausal women

Although the clinical relevance of molecular subtypes of breast cancer has been documented, little is known about risk factors for different tumor subtypes, especially the HER2-overexpressing and the triple-negative subtypes that have poor prognoses. Obesity may be differentially related to the risk of different subtypes given the various potential mechanisms underlying its association with breast cancer. We pooled two population-based case-control studies of postmenopausal breast cancer for an analysis, including 1,447 controls and 1,008 luminal (hormone receptor positive), 39 HER2-overexpressing (hormone receptor negative, HER2 positive), and 77 triple-negative (hormone receptor and HER2 negative) cases. Associations between anthropometric factors and the risk of different breast cancer subtypes were evaluated using polytomous logistic regression. Among women not currently using menopausal hormone therapy, body mass index (BMI) and weight were associated with the risk of luminal tumors [odds ratio (OR) comparing highest versus lowest quartiles, 1.7; 95% confidence interval (95% CI), 1.2-2.4 and OR, 1.7; 95% CI, 1.2-2.4, respectively] and suggestively associated with risk of triple-negative tumors (OR, 2.7; 95% CI, 1.0-7.5 and OR, 5.1; 95% CI, 1.1-23.0, respectively). Neither BMI nor weight was associated with the risk of any tumor subtype among hormone therapy users. The positive relationship between BMI and luminal tumors among postmenopausal women not using hormone therapy is well characterized in the literature. Although our sample size was limited, body size may also be related to the risk of postmenopausal triple-negative breast cancer among nonusers of hormone therapy. Given the expanding obesity epidemic, the widespread cessation of hormone therapy use, and the poor prognosis of triple-negative tumors, this novel finding merits confirmation.

Tumor size is an unreliable predictor of prognosis in basal-like breast cancers and does not correlate closely with lymph node status

Larger breast tumors tend to be associated with a greater number of axillary lymph nodes involved with metastatic tumor than are smaller tumors. This rule may not fully apply in BRCA1-related breast cancers. We hypothesized that the rule also might not apply in basal-like breast cancers (BLBC), and further, that disruption of this relationship would impact on prognosis. In 1,324 non-BLBC (87.1% of 1520 tumors), after adjustment for grade, a strongly positive correlation between increasing tumor size and increasing number of lymph nodes involved by tumor was observed (P for trend <.001). The correlation was much weaker in 196 BLBC (12.9%) (P for trend = 0.58). Similarly, a worsening breast cancer-specific survival with increasing tumor size was observed in non-BLBC (P for trend <.001) but not in BLBC (P for trend = 0.43). The "size-nodes" relationship in BLBC is distinct and is similar to that seen in BRCA1-related breast cancer, further suggesting biological similarities between these sub-types of breast cancer. Moreover, tumor size is not a strong indicator of prognosis in BLBC.

Race and triple negative threats to breast cancer survival: a population-based study in Atlanta, GA

BACKGROUND

Breast cancers with a triple negative tumor (TNT) subtype (as defined by lacking protein expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2)) preclude the use of available targeted therapies and may contribute to poor outcome and to the historically poorest survival observed among African-American (AA) women. This study examines association of the ER/PR/HER2 subtypes with race and breast cancer survival.

METHODS

Breast tumors from a population-based cohort of 116 AA and 360 white Atlanta women aged 20-54, diagnosed from 1990 to 1992 were centrally reviewed and tested by immunohistochemistry. Multivariate survival analyses within subtypes (TNT, ER-PR-HER2+, ER+/PR+HER2+, ER+/PR+HER2-) were conducted using weighted Cox regression and included socio-demographic, prognostic, and treatment factors.

RESULTS

TNTs were more prevalent among young women and particularly among AA women (Odds Ratio [OR] = 1.9, 95% Confidence Interval [CI] 1.2-2.9), adjusting for age, stage, grade, and poverty index. Overall mortality was higher for AA women (Hazard Ratio [HR] = 1.9, 95% CI, 1.5-2.5) and differed by subtypes (P < 0.001). Within the TNT subtype, racial differences in survival persisted, after additional adjustment for treatment and comorbidities (HR = 2.0, 95% CI 1.0-3.7). TNTs were uniquely associated with high expression of p16, p53, and Cyclin E; and low Bcl-2 and Cyclin D1 expression.

CONCLUSIONS

The high prevalence of TNTs among younger women and particularly younger AA women, along with unique protein expression patterns and poorer survival, suggests varying gene-environment etiologies with respect to age and race/ethnicity and a need for effective therapies.

Gene expression analyses in breast cancer epidemiology: the Norwegian Women and Cancer postgenome cohort study

Introduction

The introduction of high-throughput technologies, also called -omics technologies, into epidemiology has raised the need for high-quality observational studies to reduce several sources of error and bias.

Methods

The Norwegian Women and Cancer (NOWAC) postgenome cohort study consists of approximately 50,000 women born between 1943 and 1957 who gave blood samples between 2003 and 2006 and filled out a two-page questionnaire. Blood was collected in such a way that RNA is preserved and can be used for gene expression analyses. The women are part of the NOWAC study consisting of 172,471 women 30 to 70 years of age at recruitment from 1991 to 2006 who answered one to three questionnaires on diet, medication use, and lifestyle. In collaboration with the Norwegian Breast Cancer Group, every NOWAC participant born between 1943 and 1957 who is admitted to a collaborating hospital for a diagnostic biopsy or for surgery of breast cancer will be asked to donate a tumor biopsy and two blood samples. In parallel, at least three controls are approached for each breast cancer case in order to obtain blood samples from at least two controls per case. The controls are drawn at random from NOWAC matched by time of follow-up and age. In addition, 400 normal breast tissues as well as blood samples will be collected among healthy women participating at the Norwegian Mammography Screening program at the Breast Imaging Center at the University Hospital of North-Norway, Tromsø.

Results

The NOWAC postgenome cohort offers a unique opportunity (a) to study blood-derived gene expression profiles as a diagnostic test for breast cancer in a nested case-control design with adjustment for confounding factors related to different exposures, (b) to improve the reliability and accuracy of this approach by adjusting for an individual's genotype (for example, variants in genes coding for hormone and drug-metabolizing and detoxifying enzymes), (c) to study gene expression profiles from peripheral blood as surrogate tissue to biomonitor defined exposure (for example, hormone) and its association with disease risk (that is, breast cancer), and (d) to study gene variants (single nucleotide polymorphisms and copy number variations) and environmental exposure (endogenous and exogenous hormones) and their influence on the incidence of different molecular subtypes of breast cancer.

Conclusion

The NOWAC postgenome cohort combining a valid epidemiological approach with richness of biological samples should make an important contribution to the study of the etiology and system biology of breast cancer.

Abrogated response to cellular stress identifies DCIS associated with subsequent tumor events and defines basal-like breast tumors

Approximately 15%-30% of women diagnosed with ductal carcinoma in situ (DCIS) develop a subsequent tumor event within 10 years after surgical lumpectomy. To date, little is known about the molecular pathways that confer this differential risk for developing subsequent disease. In this study, we demonstrate that expression of biomarkers indicative of an abrogated response to cellular stress predicts DCIS with worse outcome and is a defining characteristic of basal-like invasive tumors. Mechanistic studies identify the Rb pathway as a key regulator of this response. Conversely, biomarkers indicative of an intact response to cellular stress are strongly associated with a disease-free prognosis. Assessment of these biomarkers in DCIS begins to allow prediction of tumor formation years before it actually occurs.