Biology and natural history of breast cancer

The diverse distribution of risk factors between breast cancer subtypes of ER, PR and HER2: a 10-year retrospective multi-center study in China

Introduction

Hormone receptors, human epidermal growth factor receptor 2 and some risk factors determine therapies and prognosis of breast cancer. The risk factors distributed differently between patients with receptors. This study aimed to investigate the distribution of risk factors between subtypes of breast cancer by the 3 receptors in Chinese native women with a large sample size.

Methods

The multi-center study analyzed 4211 patient medical records from 1999 to 2008 in 7 regions of China. Data on patients’ demographic information, risk factors (menopausal status, parity, body mass index) and receptor statuses were extracted. Breast cancer subtypes included ER (+/−), PR (+/−), HER2 (+/−), 4 ER/PR and 4 molecular subtypes. Wilcoxon and Chi-square tests were used to estimate the difference. The unconditional logistic regression model was used for analysis, and presented p-value after Bonferroni correction in the results.

Results

Compared to patients with negative progesterone receptor, the positive patients were younger at diagnosis, and reported less likely in postmenopausal status and lower parity (p<0.05). Comparing with the subtype of ER+/PR+, ER+/PR− subtype were 4-year older at diagnosis (OR = 1.02), more likely to be postmenopausal (OR = 1.91) and more likely to have >1 parity (OR = 1.36) (p<0.05); ER−/PR− subtype were more likely to be postmenopausal (OR = 1.33) and have >1 parity (OR = 1.19) (p<0.05). In contrast to the luminal A subtype, triple negative subtype had a lower BMI (OR = 0.96) and ORs of overweight and obesity reduced by >20% (p<0.05).

Conclusion

In this study, it was found that Chinese female patients did have statistically significant differences of age, menopausal status, parity and body mass index between breast cancer subtypes. Studies are warranted to further investigate the risk factors between subtypes, which was meaningful for prevention and treatment among Chinese females.

Association between chronological change of reproductive factors and breast cancer risk defined by hormone receptor status: results from the Seoul Breast Cancer Study

Lifestyle factors have been chronologically changed into western style ones, which could result in the rapid increase of breast cancer incidence in Korea. It is plausible that reproductive factors through hormonal mechanisms are differentially related to the risk of breast cancer subtypes. We investigated the association of reproductive risk factors on breast cancer by birth year groups and also evaluated the differential associations on the hormone receptor-defined subtypes. Using the data from the Seoul Breast Cancer Study (SeBCS), a multicenter case-control study, 3,332 breast cancer patients and 3,620 control subjects were analyzed. The distribution of subtypes among cases was as follows: 61.0 % estrogen receptor (ER)-positive, 51.9 % progesterone receptor (PR)-positive, and 43.4 % both ER/PR-positive status, respectively. Polytomous logistic regression and Wald tests for heterogeneity have been used across the subtypes. The frequencies of reproductive-related risk factors including early age at menarche, nulligravid, age at first full-term pregnancy (FFTP), duration of estrogen exposure before FFTP (EEBF), less number of children, never breastfeeding, and short duration of breastfeeding has increased as women were born later in both cases and controls, respectively (p trend < 0.0001. Among breast cancer patients, either ER- or PR-positive subtypes were increased in women born in 1960s compared to women born in 1940s. Early age at menarche increased the risk of breast cancer regardless of the subtypes while nulligravid, late age at FFTP, and longer duration of EEBP were associated with hormone receptor-positive cancer risk only (p heterogeneity < 0.05), which associations were stronger among women born later. Our results suggest that the associations of age at menarche, parity, age at FFTP, and duration of EEBF with breast cancer risk were different based on the hormone receptor status and birth year groups in Korea.

Impact of menstrual and reproductive factors on breast cancer risk in Japan: results of the JACC study

The incidence of breast cancer among Japanese women, a traditionally low-risk population, has increased substantially. To evaluate the association of reproductive factors with breast cancer risk, we examined 38,159 Japanese women, aged 40-79 years, who responded to a questionnaire on reproductive and other lifestyle factors from 1988 to 1990 in the Japan Collaborative Cohort Study. During an average 7.6 years of follow-up, we documented 151 incidents of breast cancers. Cox proportional hazards modeling was employed to estimate relative risks (RR) and 95% confidence intervals (CI). There was a significant decline in the risk of breast cancer with increasing parity among parous women (trend P=0.01). Women with four or more parities had a 69% lower risk than uniparous women, a reduced risk was also evident among menopausal women. Breast cancer risk tended to rise with increasing age at first delivery (trend P=0.05), the association being very apparent among menopausal women (trend P=0.02). Compared to the women who had their first delivery before age 25, those who delayed this event until after age 34 had an RR of 2.12 (95% CI: 0.72-6.21) and 3.33 (1.07-10.3) among the overall subjects and the menopausal, respectively. There was no apparent association of breast cancer risk with age at menarche or menopause. Our study concerning reproductive risk factors suggests that breast cancer in Japan is similar to that in Western countries, and that reproductive factors, particularly the number of parity and age at first delivery, might be important in the etiology of breast cancer among Japanese women.

Analysis of p53 mutations in cells taken from paraffin-embedded tissue sections of ductal carcinoma in situ and atypical ductal hyperplasia of the breast

Mutations in the p53 tumor suppressor gene are frequent in breast tumors but the implication of p53 mutations in breast cancer development remains poorly understood. In this study, we applied laser capture microdissection (LCM) microscope to histologically review and sample cells from paraffin-embedded breast tissue sections obtained from six cases of ductal carcinoma in situ (DCIS) and ten cases of atypical ductal hyperplasia (ADH). p53 mutations were detected, using single stranded conformational polymorphism (SSCP) and sequencing, in cell samples of three cases with DCIS and five cases with ADH. p53 mutations are therefore present in DCIS and ADH of the breast, considered as pre-malignant precursors to breast cancer, and some of them may represent early events in breast cancer development.

Transcriptomic changes in human breast cancer progression as determined by serial analysis of gene expression

Introduction

Genomic and transcriptomic alterations affecting key cellular processes such us cell proliferation, differentiation and genomic stability are considered crucial for the development and progression of cancer. Most invasive breast carcinomas are known to derive from precursor in situ lesions. It is proposed that major global expression abnormalities occur in the transition from normal to premalignant stages and further progression to invasive stages. Serial analysis of gene expression (SAGE) was employed to generate a comprehensive global gene expression profile of the major changes occurring during breast cancer malignant evolution.

Methods

In the present study we combined various normal and tumor SAGE libraries available in the public domain with sets of breast cancer SAGE libraries recently generated and sequenced in our laboratory. A recently developed modified t test was used to detect the genes differentially expressed.

Results

We accumulated a total of approximately 1.7 million breast tissue-specific SAGE tags and monitored the behavior of more than 25,157 genes during early breast carcinogenesis. We detected 52 transcripts commonly deregulated across the board when comparing normal tissue with ductal carcinoma in situ, and 149 transcripts when comparing ductal carcinoma in situ with invasive ductal carcinoma (P < 0.01).

Conclusion

A major novelty of our study was the use of a statistical method that correctly accounts for the intra-SAGE and inter-SAGE library sources of variation. The most useful result of applying this modified t statistics beta binomial test is the identification of genes and gene families commonly deregulated across samples within each specific stage in the transition from normal to preinvasive and invasive stages of breast cancer development. Most of the gene expression abnormalities detected at the in situ stage were related to specific genes in charge of regulating the proper homeostasis between cell death and cell proliferation. The comparison of in situ lesions with fully invasive lesions, a much more heterogeneous group, clearly identified as the most importantly deregulated group of transcripts those encoding for various families of proteins in charge of extracellular matrix remodeling, invasion and cell motility functions.

Differential effects of reproductive factors on the risk of pre- and postmenopausal breast cancer. Results from a large cohort of French women

The aim of this study was to obtain a better understanding of the role of hormonal factors in breast cancer risk and to determine whether the effect of reproductive events differs according to age at diagnosis. It analysed the effect of age at menarche, age at first full-term pregnancy, number of full-term pregnancies and number of spontaneous abortions both on the overall risk of breast cancer and on its pre- or postmenopausal onset, using the data on 1718 breast cancer cases, obtained from a large sample of around 100000 French women participating in the E3N cohort study. The results provide further evidence that the overall risk of breast cancer increases with decreasing age at menarche, increasing age at first pregnancy and low parity. No overall effect of spontaneous abortions was observed. The effect of these reproductive factors differed according to menopausal status. Age at menarche had an effect on premenopausal breast cancer risk, with a decrease in risk with increasing age of 7% per year (P<0.05). Compared to those who had their first menstrual periods at 11 or before, women experiencing menarche at 15 or after had an RR of 0.66 (95% CI 0.45-0.97) in the premenopausal group. Age at first full-term pregnancy had an effect on both pre- and postmenopausal breast cancer risk, with significant tests showing increasing risk per year of increasing age (P=0.001 and P<0.05 respectively). A first full-term pregnancy above age 30 conveyed a risk of 1.63 (95% CI 1.12-2.38) and 1.35 (95% CI 1.02-1.78) in the pre- and postmenopausal groups respectively. A protective effect of high parity was observed only for postmenopausal breast cancer risk (P for trend test =0.001), with point estimates of 0.79 (95% CI 0.60-1.04), 0.69 (95% CI 0.54-0.88), 0.66 (95% CI 0.51-0.85) and 0.64 (95% CI 0.48-0.86) associated to a one, two, three and four or more full-term pregnancies. A history of spontaneous abortion had no significant effect on the risk of breast cancer diagnosed before or after menopause. Our results suggest that reproductive events have complex effects on the risk of breast cancer.

Reproductive factors and breast cancer risk. Do they differ according to age at diagnosis?

Studies yielding results on risk factors stratified by age at diagnosis or menopausal status were reviewed to better understand the role of hormonal factors and to determine whether reproductive events influence breast cancer risk differently according to age at diagnosis of breast cancer. Through a Medline/Pubmed search, 26 articles providing risk estimates by age at diagnosis of breast cancer or by menopausal status were analysed. A decrease of about 9% of breast cancer risk was found for each additional year at menarche when breast cancer was diagnosed early or before the menopause, and of about 4% when diagnosed late or after. Breast cancer risk increased with increasing age at FFTP by 5% per year for breast cancer diagnosed early or before the menopause and by 3% for cancers diagnosed late or after the menopause. Each full term pregnancy (or child) led to a 3% reduction in the risk of breast cancer diagnosed early or before the menopause, whereas the reduction attained 12% for the breast cancers diagnosed later. No change in the effect of these three factors with time (date of diagnosis of the breast cancer before 1980 or after) was observed. These results support the hypothesis of an age-specific effect of the three breast cancer risk factors considered herein, based on the time of initiation of the carcinogenic process. These observations underline the importance of the time of initiation of the carcinogenic process in determining the effect of promoters such as reproductive factors. This largely unexplored aspect of breast carcinogenesis might open the way for new prevention approaches.

Cytogenetic clues to breast carcinogenesis

The somatic mutation theory of cancer maintains that tumorigenesis is driven by genetic alterations, many of which are visible cytogenetically. We have examined breast cancer by chromosome banding analysis after short-term culturing of tumor cells and here review our findings in 322 karyotypically abnormal samples obtained since 1992 from 256 patients. The screening capabilities of this technique enabled us to identify several cytogenetic subgroups of breast cancer, to study the intratumor heterogeneity of breast carcinomas, and to compare primary tumors with their metastases. Using chromosome abnormalities as clonality markers, we could determine on an individual basis when multiple, ipsilateral or bilateral breast, tumors were independent de novo carcinomas and when they resulted from the spreading of a single malignant clone within one breast or from one breast to the other. The distribution of chromosomal breakpoints and genomic gains and losses is clearly nonrandom in breast cancer, something that can guide further investigations using molecular methods. Based on the total dataset, we propose a multipathway model of mammary carcinogenesis that takes into consideration the genetic heterogeneity revealed by the karyotypic findings and review the karyotypic-pathologic correlations and the possible clinical applications of the cytogenetic knowledge.

Cytogenetic evaluation of 20 primary breast carcinomas

Chromosome analysis was performed on samples from 20 Brazilian patients with breast cancer. All the samples were from untreated patients who presented the clinical symptoms for months or years before surgical intervention. Six cases showed axillary lymph node metastases. Clonal chromosome abnormalities were detected in all cases. The numerical alterations most frequently observed involved the loss of chromosomes X, 19, 20, and 22 followed by gain of chromosomes 9 and 8. Among the structural anomalies observed, there was preferential involvement of chromosomes 11, 6, 1, 7, 3, and 12, supporting previous reports that these chromosomes may harbour genes of importance in the development of breast tumors. Two cases with a family history of breast cancer had in common total or partial trisomy 1.

Tumour development, histology and grade of breast cancers: prognosis and progression

Using 1,973 breast tumours from women aged 40-69 participating in the Swedish two-county trial of mammographic screening for breast cancer, we examined the effect of histological type on prognosis and sojourn time (the duration of the preclinical screen-detectable phase) by age. The hypothesis of dedifferentiation, according to which a cancer of mixed malignancy grade drifts towards grade 3 as the more poorly differentiated part of the tumour grows faster than the well-differentiated part, was also assessed. Ductal carcinoma in situ, invasive ductal carcinoma of grade 1, mucinous carcinoma and tubular carcinoma were all associated with good survival. Ductal carcinoma of grade 3 was associated with poor survival. Ductal carcinoma of grade 2, lobular and medullary carcinoma were associated with intermediate survival. These patterns were much the same in women aged 40-49 as in women aged 50-69. In women aged 40-49, sojourn time was estimated at about 2 years regardless of histological type. For women aged 50-69, there was a marked association of sojourn time with histological type, the shortest sojourn time being observed for lobular (2 years) and medullary (1.2 years) carcinoma, and the longest for ductal carcinoma grade 1 (7.7 years) and tubular carcinoma (7.1 years). There was strong evidence of a potential to dedifferentiation. A mover-stayer mixture of Markov chain models estimated that, in women aged 40-54, 91% of ductal tumours have the potential to dedifferentiate and, in women aged 55-69, 38% of ductal tumours have such a potential.

Epidemiology of in situ and invasive breast cancer in women aged under 45

The incidence of in situ breast cancer in the USA has increased rapidly in recent years, even among young women. A population-based case-control study of 1616 breast cancer cases aged under 45 in the USA was used to examine risk factors for in situ, local and regional/distant tumours. Almost 60% of in situ tumours were detected by routine mammograms compared with 18% of local tumours and 8% of regional/distant tumours. After adjustment for screening history and established risk factors, family history of breast cancer in a first-degree relative and African-American race were associated with an increased risk of all stages of breast cancer. The associations with nulliparity, a previous breast biopsy and body mass index were significantly stronger for in situ tumours than for local or regional/distant disease. Alcohol consumption was associated with an increasing trend in risk of regional/distant tumours but not of earlier stage tumours, indicating that alcohol may be involved in late-stage events. Analyses by histological type of in situ tumours suggested that both ductal and lobular carcinoma in situ were associated with most established breast cancer risk factors, and the magnitude of association tended to be greater for the ductal form.

Breast cancer: prognostic significance of c-erb-B2 and int-2 amplification compared with DNA ploidy, S-phase fraction, and conventional clinicopathological features

The prognostic value of oncogene amplification and conventional clinicopathological features was determined in consecutive breast cancers detected during 5 months in 1975-1976 in 4 Swedish counties. Material was collected from 162 of the 179 patients and tumor size, nodal status, FSH, estrogen/progesterone receptor status, DNA ploidy and S-phase fraction determined. Tissues remaining from 80 patients were stored frozen until 1991, when amplification of the oncogenes c-erb-B2 and int-2 was determined. We show that c-erb-B2 amplification (but not int-2 amplification) and positive axillary nodal status show prognostic significance for both survival and relapse-free survival in univariate and multivariate analysis. The other examined factors showed no significance.

An alternative approach for treatment of breast cancer

Since adjuvant chemotherapy and hormonal therapy generally extend disease free survival in breast cancer rather than provide a cure, we have examined the current breast cancer paradigm. Heterogeneity is a fundamental characteristic of breast cancer tissue and a well recognized aspect of the disease. There are variations in natural history, histopathology, biochemistry and endocrinology, and molecular biology of cancer tissues and cells within the tissues. A variety of data indicate that growth kinetics are also variable, not only from tumor to tumor, but also during the natural history of an individual's tumor. To better understand kinetic heterogeneity, a stochastic numeric computer model of the natural history of breast cancer has been developed. To be consistent with inter- and intratumor kinetic heterogeneity and with late relapse, the model predicts that tumors grow in an irregular fashion with alternating periods of growth and periods of dormancy rather than the generally accepted modified exponential, or Gompertzian fasion. The prediction of irregular growth has been compared to data relevant to growth characteristics of human breast cancer. Much data support the concept of irregular kinetics and temporary dormancy rather than steady, Gompertzian growth of human breast cancer. Thus, in addition to drug resistance, kinetic heterogeneity may help explain the limited impact that traditional chemotherpeutic treatment has had on mortality from breast cancer. Although the mechanisms underlying irregular growth need to be better understood, non-Gompertzian growth kinetics indicates that there may be alternative approaches for breast cancer treatment.

Development of breast cancer chemopreventive drugs

Breast cancer is the second highest cause of cancer mortality (19%) estimated for U.S. women in 1993 and accounts for the highest proportion of new cancer cases (32%) in this population. The rate of documented cases increased during the early 1970s and again in 1980-87, probably due to early mammographic detection. Increased knowledge of personal risk may also have been a consideration; however, 60% of women diagnosed with breast cancer have no known risk factor(s), such as family history, early age at menarche, late age at menopause, nulliparity, late age at first live birth, socioeconomic status, contraceptive use, postmenopausal estrogen replacement, or high fat intake. To prevent cancer, one strategy undertaken by the NCI is cancer chemoprevention, or intervention with chemical agents at the precancer stage to halt or slow the carcinogenic process. An objective of the NCI, DCPC is to develop promising cancer chemopreventive chemical agents as drugs for human use. Briefly, the process begins with identification of potential agents (e.g., pharmaceuticals, natural products, minor dietary constituents) from surveillance and analysis of the literature and from in vitro prescreen assays. Data on both efficacy (i.e., biological activities that either directly or indirectly indicate inhibition of carcinogenesis) and toxicity are gathered these sources. Various criteria are used to select and prioritize agents for entry into the NCI, DCPC preclinical testing program. The program begins with battery of in vitro efficacy screens using both animal and human cells to select agents for further testing; agents positive in these assays are considered for further testing. In the assay used for breast cancer chemoprevention, 7,12-dimethylbenz(a)anthracene (DMBA)-induced mouse mammary organ culture, 64 chemicals have inhibited formation of hyperplastic alveolar-like nodules. A panel of organ-specific animal screening assays are then used to assess efficacy in vivo. Two assays relevant for breast cancer chemoprevention are inhibition of N-methyl-N-nitrosourea- and DMBA-induced rat mammary gland carcinogenesis. Of 89 agents tested, 29 have inhibited cancer incidence, multiplicity, or both in at least one of the mammary assays; 21 agents are currently on test. Highly promising agents are then placed in traditional preclinical toxicity tests performed in two species. Finally, the most promising and least toxic agents enter clinical trials. Phase I clinical trials are designed to investigate human dose-related safety and pharmacokinetics of the drug. Phase II trials are small scale, placebo-controlled studies designed to determine chemopreventive efficacy and optimal dosing regimens.(ABSTRACT TRUNCATED AT 400 WORDS)

A New Approach to Tumour Marker Assessment by Perioperative Determination in Breast and Colorectal Cancer

Preoperative serum tumour markers are currently classified as positive or negative according to a predetermined cut-off point. In the present study we examined the dynamic variation of marker levels after radical surgery of breast and colorectal cancer. CEA and CA15.3 were measured in 93 patients with breast cancer, CEA and CA19.9 in 97 patients with colorectal carcinoma before and 30 days after radical surgery. Any variation higher than 3-fold the analytical coefficient of variation of the assay was considered significant. In patients with negative preoperative marker levels a significant decrease was noted after surgery in 15.6% of cases for CEA and 27.8% for CA15.3 in breast cancer and in 46.8% for CEA and 25.7% for CA19.9 in colorectal cancer. Using both cut-off-based and dynamic criteria, we found an overall positivity rate of 19.6% for CEA and 33.3% for CA15.3 in breast cancer; 60.0% for CEA and 37.1% for CA19.9 in colorectal cancer.

From the present findings we conclude that the dynamic study of perioperative variations of tumour markers is a sensitive method additional to cut-off-based criteria for the assessment of the phenotypic expression of the marker by the tumour.

Mammography

A comparison is made of breast cancer mortality in women included in a mammography screening program, including those who refused to attend, and women who were not included--even those who underwent voluntary mammography. About 215,000 women in five different studies showed between 4 and 24% reduction of mortality; however, this was significant in only two of the studies. No significant reduction was seen in those under 50 yr of age.