Estimate of tumor growth time for breast cancer local recurrences: rapid growth after wake-up?

Impact of Chemotherapeutic Stress Depends on The Nature of Breast Cancer Spheroid and Induce Behavioral Plasticity to Resistant Population

Cellular or tumor dormancy, identified recently as one of the main reasons behind post-therapy recurrence, can be caused by diverse reasons. Chemotherapy has recently been recognized as one of such reasons. However, in-depth studies of chemotherapy-induced dormancy are lacking due to the absence of an in vitro human-relevant model tailor-made for such a scenario. This report utilized multicellular breast cancer spheroid to create a primary platform for establishing a chemotherapy-induced dormancy model. It is observed that extreme chemotherapeutic stress affects invasive and non-invasive spheroids differently. Non-invasive spheroids exhibit more resilience and maintain viability and migrational ability, while invasive spheroids display heightened susceptibility and improved tumorigenic capacity. Heterogenous spheroids exhibit increased tumorigenic capacity while show minimal survival ability. Further probing of chemotherapeutically dormant spheroids is needed to understand the molecular mechanism and identify dormancy-related markers to achieve therapeutic success in the future.

Clinical Tumor Dormancy

This chapter summarizes clinical evidence on tumor dormancy, with a special focus on our research supporting the role of dormancy both in local and distant recurrence of breast cancer following mastectomy. Starting from these premises, we propose a model of neoplastic development that allows us to elucidate several relevant clinical phenomena, including the mammographic paradox, the significance of ipsilateral breast tumor recurrence after conservative surgery, and the effect of surgeries performed after the removal of the primary. We will discuss the biological implications of the dormancy-based model, which are at odds with Somatic Mutation Theory. We will then review new models, alternatives to the Somatic Mutation Theory, for cancer development, with special emphasis on the Dynamic System Theory and the originality of its conceptual approach. Finally, we will put particular emphasis on the view of cancer development as a tissue-level process. We believe that this will help harmonize the molecular biology research with the new conceptual approach and bridge the knowledge gap on dormancy between bench and bedside.

COMMD3 loss drives invasive breast cancer growth by modulating copper homeostasis

BACKGROUND

Despite overall improvement in breast cancer patient outcomes from earlier diagnosis and personalised treatment approaches, some patients continue to experience recurrence and incurable metastases. It is therefore imperative to understand the molecular changes that allow transition from a non-aggressive state to a more aggressive phenotype. This transition is governed by a number of factors.

METHODS

As crosstalk with extracellular matrix (ECM) is critical for tumour cell growth and survival, we applied high throughput shRNA screening on a validated '3D on-top cellular assay' to identify novel growth suppressive mechanisms.

RESULTS

A number of novel candidate genes were identified. We focused on COMMD3, a previously poorly characterised gene that suppressed invasive growth of ER + breast cancer cells in the cellular assay. Analysis of published expression data suggested that COMMD3 is normally expressed in the mammary ducts and lobules, that expression is lost in some tumours and that loss is associated with lower survival probability. We performed immunohistochemical analysis of an independent tumour cohort to investigate relationships between COMMD3 protein expression, phenotypic markers and disease-specific survival. This revealed an association between COMMD3 loss and shorter survival in hormone-dependent breast cancers and in particularly luminal-A-like tumours (ER+/Ki67-low; 10-year survival probability 0.83 vs. 0.73 for COMMD3-positive and -negative cases, respectively). Expression of COMMD3 in luminal-A-like tumours was directly associated with markers of luminal differentiation: c-KIT, ELF5, androgen receptor and tubule formation (the extent of normal glandular architecture; p < 0.05). Consistent with this, depletion of COMMD3 induced invasive spheroid growth in ER + breast cancer cell lines in vitro, while Commd3 depletion in the relatively indolent 4T07 TNBC mouse cell line promoted tumour expansion in syngeneic Balb/c hosts. Notably, RNA sequencing revealed a role for COMMD3 in copper signalling, via regulation of the Na+/K+-ATPase subunit, ATP1B1. Treatment of COMMD3-depleted cells with the copper chelator, tetrathiomolybdate, significantly reduced invasive spheroid growth via induction of apoptosis.

CONCLUSION

Overall, we found that COMMD3 loss promoted aggressive behaviour in breast cancer cells.

Molecular changes during extended neoadjuvant letrozole treatment of breast cancer: distinguishing acquired resistance from dormant tumours

BACKGROUND

The risk of recurrence for endocrine-treated breast cancer patients persists for many years or even decades following surgery and apparently successful adjuvant therapy. This period of dormancy and acquired resistance is inherently difficult to investigate; previous efforts have been limited to in-vitro or in-vivo approaches. In this study, sequential tumour samples from patients receiving extended neoadjuvant aromatase inhibitor therapy were characterised as a novel clinical model.

METHODS

Consecutive tumour samples from 62 patients undergoing extended (4-45 months) neoadjuvant aromatase inhibitor therapy with letrozole were subjected to transcriptomic and proteomic analysis, representing before (≤ 0), early (13-120 days), and long-term (> 120 days) neoadjuvant aromatase inhibitor therapy with letrozole. Patients with at least a 40% initial reduction in tumour size by 4 months of treatment were included. Of these, 42 patients with no subsequent progression were classified as "dormant", and the remaining 20 patients as "acquired resistant".

RESULTS

Changes in gene expression in dormant tumours begin early and become more pronounced at later time points. Therapy-induced changes in resistant tumours were common features of treatment, rather than being specific to the resistant phenotype. Comparative analysis of long-term treated dormant and resistant tumours highlighted changes in epigenetics pathways including DNA methylation and histone acetylation. The DNA methylation marks 5-methylcytosine and 5-hydroxymethylcytosine were significantly reduced in resistant tumours compared with dormant tissues after extended letrozole treatment.

CONCLUSIONS

This is the first patient-matched gene expression study investigating long-term aromatase inhibitor-induced dormancy and acquired resistance in breast cancer. Dormant tumours continue to change during treatment whereas acquired resistant tumours more closely resemble their diagnostic samples. Global loss of DNA methylation was observed in resistant tumours under extended treatment. Epigenetic alterations may lead to escape from dormancy and drive acquired resistance in a subset of patients, supporting a potential role for therapy targeted at these epigenetic alterations in the management of resistance to oestrogen deprivation therapy.

Engineered In Vitro Models of Tumor Dormancy and Reactivation

Metastatic recurrence is a major hurdle to overcome for successful control of cancer-associated death. Residual tumor cells in the primary site, or disseminated tumor cells in secondary sites, can lie in a dormant state for long time periods, years to decades, before being reactivated into a proliferative growth state. The microenvironmental signals and biological mechanisms that mediate the fate of disseminated cancer cells with respect to cell death, single cell dormancy, tumor mass dormancy and metastatic growth, as well as the factors that induce reactivation, are discussed in this review. Emphasis is placed on engineered, in vitro, biomaterial-based approaches to model tumor dormancy and subsequent reactivation, with a focus on the roles of extracellular matrix, secondary cell types, biochemical signaling and drug treatment. A brief perspective of molecular targets and treatment approaches for dormant tumors is also presented. Advances in tissue-engineered platforms to induce, model, and monitor tumor dormancy and reactivation may provide much needed insight into the regulation of these processes and serve as drug discovery and testing platforms.

Association of breast carcinoma growth with a non-canonical axis of IFNγ/IDO1/TSP1

Reciprocal interactions between cancers and the surrounding microenvironment have an important role in tumour evolution. In this study, our data suggested that through thrombospondin 1 (TSP1), tumour-associated microvessel provides a dormant niche to sustain inactive status of breast invasive ductal carcinoma (IDC) cells. TSP1 levels in the tumour stroma were negatively correlated with vascular indoleamine 2,3-dioxygenase 1 (IDO1) in IDC tissues. IDO1 is an intracellular enzyme initiating the first and rate-limited step of tryptophan breakdown. Lower stromal TSP1 levels and positive tumour vascular IDO1 staining seems to associate with poor survive of patients with IDC. IDC cells induced a significantly increase in IDO1 expression in endothelial cells (ECs). IFNγ exerts a similar effect on ECs. We hypothesized a tryptophan starvation theory that since tryptophan is essential for the synthesis of TSP1, IDO1 induce a decrease in tryptophan availability and a reduction in TSP1 synthesis in ECs, leading to overcoming the dormancy state of IDC cells and exacerbating conditions such as tumour invasion and metastasis. These findings identify a non-canonical role of IFNγ/IDO1/TSP1 axis in microvascular niche-dominated dormancy of breast invasive ductal carcinoma with a solid foundation for further investigation of therapeutic and prognostic relevance.

Imaging Sensitivity of Quiescent Cancer Cells to Metabolic Perturbations in Bone Marrow Spheroids

Malignant cells from breast cancer and other common cancers such as prostate and melanoma may persist in bone marrow as quiescent, non-dividing cells that remain viable for years or even decades before resuming proliferation to cause recurrent disease. This phenomenon, referred to clinically as tumor dormancy, poses tremendous challenges to curing patients with breast cancer. Quiescent tumor cells resist chemotherapy drugs that predominantly target proliferating cells, limiting success of neo-adjuvant and adjuvant therapies. We recently developed a 3D spheroid model of quiescent breast cancer cells in bone marrow for mechanistic and drug testing studies. We combined this model with optical imaging methods for label-free detection of cells preferentially utilizing glycolysis versus oxidative metabolism to investigate the metabolic state of co-culture spheroids with different bone marrow stromal and breast cancer cells. Through imaging and biochemical assays, we identified different metabolic states of bone marrow stromal cells that control metabolic status and flexibilities of co-cultured breast cancer cells. We tested metabolic stresses and targeted inhibition of specific metabolic pathways to identify approaches to preferentially eliminate quiescent breast cancer cells from bone marrow environments. These studies establish an integrated imaging approach to analyze metabolism in complex tissue environments to identify new metabolically-targeted cancer therapies.

Mechanisms of Cancer Cell Dormancy--Another Hallmark of Cancer?

Disease relapse in cancer patients many years after clinical remission, often referred to as cancer dormancy, is well documented but remains an incompletely understood phenomenon on the biologic level. Recent reviews have summarized potential models that can explain this phenomenon, including angiogenic, immunologic, and cellular dormancy. We focus on mechanisms of cellular dormancy as newer biologic insights have enabled better understanding of this process. We provide a historical context, synthesize current advances in the field, and propose a mechanistic framework that treats cancer cell dormancy as a dynamic cell state conferring a fitness advantage to an evolving malignancy under stress. Cellular dormancy appears to be an active process that can be toggled through a variety of signaling mechanisms that ultimately downregulate the RAS/MAPK and PI(3)K/AKT pathways, an ability that is preserved even in cancers that constitutively depend on these pathways for their growth and survival. Just as unbridled proliferation is a key hallmark of cancer, the ability of cancer cells to become quiescent may be critical to evolving malignancies, with implications for understanding cancer initiation, progression, and treatment resistance.

A signature of epithelial-mesenchymal plasticity and stromal activation in primary tumor modulates late recurrence in breast cancer independent of disease subtype

Introduction

Despite improvements in adjuvant therapy, late systemic recurrences remain a lethal consequence of both early- and late-stage breast cancer. A delayed recurrence is thought to arise from a state of tumor dormancy, but the mechanisms that govern tumor dormancy remain poorly understood.

Methods

To address the features of breast tumors associated with late recurrence, but not confounded by variations in systemic treatment, we compiled breast tumor gene expression data from 4,767 patients and established a discovery cohort consisting of 743 lymph node-negative patients who did not receive systemic neoadjuvant or adjuvant therapy. We interrogated the gene expression profiles of the 743 tumors and identified gene expression patterns that were associated with early and late disease recurrence among these patients. We applied this classification to a subset of 46 patients for whom expression data from microdissected tumor epithelium and stroma was available, and identified a distinct gene signature in the stroma and also a corresponding tumor epithelium signature that predicted disease recurrence in the discovery cohort. This tumor epithelium signature was then validated as a predictor for late disease recurrence in the entire cohort of 4,767 patients.

Results

We identified a novel 51-gene signature from microdissected tumor epithelium associated with late disease recurrence in breast cancer independent of the molecular disease subtype. This signature correlated with gene expression alterations in the adjacent tumor stroma and describes a process of epithelial to mesenchymal transition (EMT) and tumor-stroma interactions.

Conclusions

Our findings suggest that an EMT-related gene signature in the tumor epithelium is related to both stromal activation and escape from disease dormancy in breast cancer. The presence of a late recurrence gene signature in the primary tumor also suggests that intrinsic features of this tumor regulate the transition of disseminated tumor cells into a dormant phenotype with the ability to outgrowth as recurrent disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0407-9) contains supplementary material, which is available to authorized users.

What can be learnt about disease progression in breast cancer dormancy from relapse data?

Breast cancer patients have an anomalously high rate of relapse many years–up to 25 years–after apparently curative surgery removed the primary tumour. Disease progression during the intervening years between resection and relapse is poorly understood. There is evidence that the disease persists as dangerous, tiny metastases that remain at a growth restricted, clinically undetectable size until a transforming event restarts growth. This is the starting point for our study, where patients who have metastases that are all tiny and growth-restricted are said to have cancer dormancy. Can long-term follow-up relapse data from breast cancer patients be used to extract knowledge about the progression of the undetected disease? Here, we evaluate whether this is the case by introducing and analysing four simple mathematical models of cancer dormancy. These models extend the common assumption that a random transforming event, such as a mutation, can restart growth of a tiny, growth-restricted metastasis; thereafter, cancer dormancy progresses to detectable metastasis. We find that physiopathological details, such as the number of random transforming events that metastases must undergo to escape from growth restriction, cannot be extracted from relapse data. This result is unsurprising. However, the same analysis suggested a natural question that does have a surprising answer: why are interesting trends in long-term relapse data not more commonly observed? Further, our models indicate that (a) therapies which induce growth restriction among metastases but do not prevent increases in metastases' tumourigenicity may introduce a time post-surgery when more patients are prone to relapse; and (b), if a number of facts about disease progression are first established, how relapse data might be used to estimate clinically relevant variables, such as the likely numbers of undetected growth-restricted metastases. This work is a necessary, early step in building a quantitative mechanistic understanding of cancer dormancy.

The molecular genomics of metastatic brain tumours

INTRODUCTION

Metastatic brain tumours remain an intractable clinical problem despite notable advances in the treatment of the primary cancers. It is estimated that 30-40% of breast and lung cancer patients will develop brain metastases. Typically, brain lesions are not diagnosed until patients exhibit neurological symptoms because there are currently no tests that can predict which patients will be afflicted. Brain metastases are resistant to current chemotherapies, and despite surgical resection and radiotherapy, the prognosis for these patients remains very poor with an average survival of only 6-9 months. Cancer is ultimately a genetic disease, involving patient genetics and aberrant tumour genomics; therefore the pursuit of an explanation for why or how brain metastases occur requires investigation of the associated somatic mutations. In this article, we review the current literature surrounding the molecular and genome-based mechanistic evidence to indicate driver oncogenes that hold potential biomarkers for risk, or therapeutic targets for treatment of brain metastases.

CONCLUSION

Patients afflicted with metastatic brain tumours are in dire need of more effective therapies, and clinicians need predictive laboratory tests to identify patients at risk of developing metastatic brain tumours. The as yet unrealized comprehensive analysis of metastatic brain tumour genomics is necessary to meet these needs. Moreover, without improved understanding of the genomic aberrations that drive metastatic brain tumours, development of biomarkers and molecularly targeted therapies will remain stalled and patient outcomes will continue to be dismal.

Promising development from translational or perhaps anti-translational research in breast cancer

Background

A great deal of the public’s money has been spent on cancer research but demonstrable benefits to patients have not been proportionate. We are a group of scientists and physicians who several decades ago were confronted with bimodal relapse patterns among early stage breast cancer patients who were treated by mastectomy. Since the bimodal pattern was not explainable with the then well-accepted continuous growth model, we proposed that metastatic disease was mostly inactive before surgery but was driven into growth somehow by surgery. Most relapses in breast cancer would fall into the surgery-induced growth category thus it was highly important to understand the ramifications of this process and how it may be curtailed. With this hypothesis, we have been able to explain a wide variety of clinical observations including why mammography is less effective for women age 40–49 than it is for women age 50–59, why adjuvant chemotherapy is most effective for premenopausal women with positive lymph nodes, and why there is a racial disparity in outcome.

Methods

We have been diligently looking for new clinical or laboratory information that could provide a connection or correlation between the bimodal relapse pattern and some clinical factor or interventional action and perhaps lead us towards methods to prevent surgery-initiated tumor activity.

Results

A recent development occurred when a retrospective study appeared in an anesthesiology journal that suggested the perioperative NSAID analgesic ketorolac seems to reduce early relapses following mastectomy. Collaborating with these anesthesiologists to understand this effect, we independently re-examined and updated their data and, in search of a mechanism, focused in on the transient systemic inflammation that follows surgery to remove a primary tumor. We have arrived at several possible explanations ranging from mechanical to biological that suggest the relapses avoided in the early years do not show up later.

Conclusions

We present the possibility that a nontoxic and low cost intervention could prevent early relapses. It may be that preventing systemic inflammation post surgery will prevent early relapses. This could be controlled by the surgical anesthesiologist’s choice of analgesic drugs. This development needs to be confirmed in a randomized controlled clinical trial and we have identified triple negative breast cancer as the ideal subset with which to test this. If successful, this would be relatively easy to implement in developing as well as developed countries and would be an important translational result.

Genomic analysis of circulating cell-free DNA infers breast cancer dormancy

Biomarkers in breast cancer to monitor minimal residual disease have remained elusive. We hypothesized that genomic analysis of circulating free DNA (cfDNA) isolated from plasma may form the basis for a means of detecting and monitoring breast cancer. We profiled 251 genomes using Affymetrix SNP 6.0 arrays to determine copy number variations (CNVs) and loss of heterozygosity (LOH), comparing 138 cfDNA samples with matched primary tumor and normal leukocyte DNA in 65 breast cancer patients and eight healthy female controls. Concordance of SNP genotype calls in paired cfDNA and leukocyte DNA samples distinguished between breast cancer patients and healthy female controls (P < 0.0001) and between preoperative patients and patients on follow-up who had surgery and treatment (P = 0.0016). Principal component analyses of cfDNA SNP/copy number results also separated presurgical breast cancer patients from the healthy controls, suggesting specific CNVs in cfDNA have clinical significance. We identified focal high-level DNA amplification in paired tumor and cfDNA clustered in a number of chromosome arms, some of which harbor genes with oncogenic potential, including USP17L2 (DUB3), BRF1, MTA1, and JAG2. Remarkably, in 50 patients on follow-up, specific CNVs were detected in cfDNA, mirroring the primary tumor, up to 12 yr after diagnosis despite no other evidence of disease. These data demonstrate the potential of SNP/CNV analysis of cfDNA to distinguish between patients with breast cancer and healthy controls during routine follow-up. The genomic profiles of cfDNA infer dormancy/minimal residual disease in the majority of patients on follow-up.

Cancer dormancy: a model of early dissemination and late cancer recurrence

Cancer dormancy is a stage in tumor progression in which residual disease remains occult and asymptomatic for a prolonged period of time. Dormant tumor cells can be present as one of the earliest stages in tumor development, as well as a stage in micrometastases, and/or minimal residual disease left after an apparently successful treatment of the primary tumor. The general mechanisms that regulate the transition of disseminated tumor cells that have lain dormant into a proliferative state remain largely unknown. However, regulation of the growth from dormant tumor cells may be explained in part through the interaction of the tumor cell with its microenvironment, limitations in the blood supply, or an active immune system. An understanding of the regulatory machinery of these processes is essential for identifying early cancer biomarkers and could provide a rationale for the development of novel agents to target dormant tumor cells. This review focuses on the different signaling models responsible for early cancer dissemination and tumor recurrence that are involved in dormancy pathways.

True local recurrences do not metastasize

Generally, the limits of local tumor control are in part connected with the term "field cancerization" and are known from oral, lung, prostate, or mammary cancer. With the example of breast cancer (BC), the problem of ipsilateral breast tumor recurrences (IBTR) after breast-conserving surgery will be reviewed. Three types of local recurrences are distinguished: true recurrences, new primaries, or residual tumors. Good data for BC allow the description of the time-dependent risk of these three types, relative to the diagnosis of the primary tumor, because the time of initiation and the growth duration of the IBTR can be estimated. Two hypotheses explain the data: first, local recurrences may be initiated years before the diagnosis of a primary tumor (PT) and can then appear as multifocal PT at diagnosis, and second, true local recurrences probably do not metastasize. The generalizability of these hypotheses for other tumors will be discussed.

Mathematical model of the role of intercellular signalling in intercellular cooperation during tumorigenesis

OBJECTIVES

Intercellular cooperation has been hypothesized to enhance cell proliferation during cancer metastasis through autocrine signalling cascades and mathematical models can provide valuable insights into underlying mechanisms of metastatic tumorigenesis. Here, we present a model that incorporates signal-stimulated cell proliferation, and investigate influences of diffusion-driven heterogeneity in signal concentration on proliferation dynamics.

MATERIALS AND METHODS

Our model incorporates signal production through both autocrine and paracrine pathways, and signal diffusion and loss for a metastasizing cell population at a host site. We use the signalling pathway of IL-6 for illustration where this signalling species forms an intermediate complex with its receptor IL-6R. This in turn forms a heterodimeric complex with transmembrane protein gp130, ultimately resulting in production of downstream signals. Cell population dynamics are taken to follow a modified logistic equation for which the rate term is dependent on local IL-6 concentration.

RESULTS AND CONCLUSIONS

Our spatiotemporal model agrees closely with experimental results. The model is also able to predict two phenomena typical of metastatic tumorigenesis - host tissue preference and long periods of proliferation dormancy. It confirms that diffusivity of the signalling species in a host tissue plays a significant role during the process. Our results show that the proliferation-apoptosis balance is tipped in favour of the former for host sites that have relatively smaller signal diffusivities.

Gap junction-mediated import of microRNA from bone marrow stromal cells can elicit cell cycle quiescence in breast cancer cells

Bone marrow (BM) metastasis of breast cancer (BC) can recur even decades after initial diagnosis and treatment, implying the long-term survival of disseminated cancer cells in a dormant state. Here we investigated the role of microRNAs (miRNA) transmitted from BM stroma to BC cells via gap junctions and exosomes in tumor cell quiescence. MDA-MB-231 and T47D BC cells arrest in G(0) phase of the cell cycle when cocultured with BM stroma. Analyses of miRNA expression profiles identified numerous miRNAs implicated in cell proliferation including miR-127, -197, -222, and -223 targeting CXCL12. Subsequently, we showed that these CXCL12-specific miRNAs are transported from BM stroma to BC cells via gap junctions, leading to reduced CXCL12 levels and decreased proliferation. Stroma-derived exosomes containing miRNAs also contributed to BC cell quiescence, although to a lesser degree than miRNAs transmitted via gap junctions. This study shows that the transfer of miRNAs from BM stroma to BC cells might play a role in the dormancy of BM metastases.

Does tumour dormancy offer a therapeutic target?

The increasing number of cancer survivors is cause for celebration, but this expanding population has highlighted the problem of tumour dormancy, which can lead to relapse. As we start to understand more about the biology of dormant cancer cells, we can begin to address how best to treat this form of disease. Preclinical models and initial clinical trials, as exemplified in patients with breast cancer, are paving the way to address how best to treat long-term cancer survivors to minimize the risk of cancer recurrence.

Breast cancer dormancy can be maintained by small numbers of micrometastases

Late relapse of breast cancer can occur more than 25 years after primary diagnosis. During the intervening years between initial treatment and relapse, occult cancers are maintained in an apparent state of dormancy that is poorly understood. In this study, we applied a probabilistic mathematical model to long-term follow-up studies of postresection patients to investigate the factors involved in mediating breast cancer dormancy. Our results suggest that long-term dormancy is maintained most often by just one growth-restricted dangerous micrometastasis. Analysis of the empirical data by Approximate Bayesian Computation indicated that patients in dormancy have between 1 and 5 micrometastases at 10 years postresection, when they escape growth restriction with a half-life of <69 years and are >0.4 mm in diameter. Before resection, primary tumors seed at most an average of 6 dangerous micrometastases that escape from growth restriction with a half-life of at least 12 years. Our findings suggest that effective preventive treatments will need to eliminate these small numbers of micrometastases, which may be preangiogenic and nonvascularized until they switch to growth due to one oncogenic mutation or tumor suppressor gene inactivation. In summary, breast cancer dormancy seems to be maintained by small numbers of sizeable micrometastases that escape from growth restriction with a half-life exceeding 12 years.

Recurrence and mortality dynamics for breast cancer patients undergoing mastectomy according to estrogen receptor status: different mortality but similar recurrence

(Cancer Sci 2010; 101: 826-830) The purpose was to ascertain whether the recurrence risk patterns for patients with estrogen receptor (ER)-positive (P) and ER-negative (N) breast cancer support the ER-related clinical divergence suggested by the observed different mortality patterns and gene expression profiles. Both recurrence and death were considered in a series of 771 patients undergoing mastectomy. ER status was available for 539 patients. The hazard rates for recurrence and mortality throughout 15 years of follow-up were assessed. The recurrence dynamics displays a bimodal pattern for both ERP and ERN tumors with comparable peak timings. The two curves cross during the 3rd year. By contrast, the mortality dynamics are definitely different for ERP and ERN tumors: during the early follow-up period ERN patients have their highest mortality risk, while ERP patients have their lowest mortality risk. The two curves cross during the 5th year. In spite of the different mortality dynamics, the recurrence dynamics do not demonstrate a major distinction in timing between ERP and ERN breast cancers, suggesting that the metastasis development process following mastectomy is apparently similar for both ER categories. The observed differences in the mortality risk are plausibly attributable to ER-related factors influencing the clinical course from recurrence to death. These clinical findings apparently contradict the occurrence of two different types of breast cancer, notwithstanding the distinct epidemiological, clinical, and molecular features linked to ERP and ERN tumors, although ER levels may concur to establish the event risk levels.

Immune, endocrine, and behavioral precursors to breast cancer recurrence: a case-control analysis

BACKGROUND

A period of tumor growth precedes the clinical detection of breast cancer recurrence. We explore immune, endocrine, and behavioral parameters during this period.

METHODS

We conducted a phase III clinical trial in which women with surgically treated stage II/III breast cancer (N = 227) were randomized to receive a psychological intervention or assessment-only and then regularly assessed for 10 years. Patients who recurred (R, n = 48) were matched with patients remaining disease-free (DF, n = 48) on demographic and prognostic characteristics, treatment, and duration of disease-free follow-up. Data at three assessment points, occurring, on average, 17, 11, and 4 months before the recurrence was detected clinically, with equivalent time points for the disease-free group, were examined. Mixed-effects models tested for group differences in immune cell counts and function as well as endocrine and behavioral parameters.

RESULTS

In the 17 months prior to recurrence detection, patients exhibited higher white blood cell count, neutrophil, lymphocyte, and natural killer cell counts, relative to DF patients. R patients also showed higher cortisol, worse physical functioning, fatigue, and quality of life. Follow-up analyses showed patients with local recurrences to differ from those with distant recurrence, with the former exhibiting elevated natural killer cell cytotoxicity, lymphocyte proliferative response, fatigue, pain, and emotional distress (depression, anxiety), and the latter exhibiting higher neutrophil, lymphocyte, and natural killer cell counts.

CONCLUSION

Patients who would recur showed reliable biobehavioral alterations more than a year prior to their diagnosis. This novel observation may contribute to our understanding of the disease relapse processes.

Tumor dormancy and surgery-driven interruption of dormancy in breast cancer: learning from failures

Primary tumor removal, usually considered intrinsically beneficial, can perturb metastatic homeostasis, and for some patients results in the acceleration of metastatic cancer. The continuous-growth model is required to yield to an interrupted-growth model, the implications of which are episodes of tumor dormancy. This Review analyzes the recent evolution of two paradigms related to the development of breast cancer metastases. The evolution of the paradigms described herein is supported by a growing body of findings from experimental models, and is required to explain breast cancer recurrence dynamics for patients undergoing surgery with or without adjuvant chemotherapy.

Tumour dormancy in breast cancer: an update

Delayed recurrences, common in breast cancer, are well explained by the concept of tumour dormancy. Numerous publications describe clinical times to disease recurrence or death, using mathematical approaches to infer mechanisms responsible for delayed recurrences. However, most of the clinical literature discussing tumour dormancy uses data from over a half century ago and much has since changed. This review explores how current breast cancer treatment could change our understanding of the biology of breast cancer tumour dormancy, and summarizes relevant experimental models to date. Current knowledge gaps are highlighted and potential areas of future research are identified.

Maintenance Therapy to Suppress Micrometastasis: The New Challenge for Adjuvant Cancer Treatment

The palliative efficacy of cytotoxic drugs is routinely assessed using tumor shrinkage (response) rates shown in clinical trials. Although adjuvant drug therapy has a goal distinct from that of palliative therapy (i.e., to prolong survival by inhibiting progression of micrometastatic disease), it is widely assumed that the adjuvant efficacy of a drug will parallel its response rate ("activity") in advanced stages of the disease. Reconsideration of this assumption seems timely in view of recent developments: the realization that many predictors of short-term tumor response correlate inversely with long-term survival outcomes; the characterization of tumor progression as a discontinuous process that may include dormant phases; the understanding that micrometastasis is therapeutically suppressible by a variety of mechanisms including direct tumor cell kill, cytotoxic disruption of paracrine growth signals from normal tissues, and targeted inhibition of prometastatic pathways; the recognition that tumor dormancy not only blocks the antimetastatic efficacy of cytotoxic drugs but also represents a therapeutic end point for metastasis-suppressive noncytotoxic drugs such as hormone inhibitors; and the insight that optimal adjuvant drug therapy is likely to include both induction and maintenance components. The traditional view of cytoreductive response as a prerequisite for adjuvant drug efficacy thus merits reappraisal, with a view to accelerating incorporation of novel noncytotoxic maintenance therapies into controlled studies.

Breast cancer recurrence dynamics following adjuvant CMF is consistent with tumor dormancy and mastectomy-driven acceleration of the metastatic process

PURPOSE

The aim of this study was to better understand human breast cancer biology by studying how the timing of metastasis following primary resection is affected by adjuvant CMF (cyclophoshamide, methotrexate, 5-fluorouracil) chemotherapy.

PATIENTS AND METHODS

Discrete hazards of recurrence and recurrence risk reductions for treated patients relative to controls were analyzed for all patients enrolled in two separate randomized clinical trials [study 1 (386 women): no further treatment versus 12 cycles of CMF; study 2 (459 women): six versus 12 cycles of CMF] and a historical group (396 women: surgery alone) of axillary node-positive patients undergoing mastectomy.

RESULTS

(i) Nearly all CMF benefit occurs during the first 4 years following resection/chemotherapy. (ii) The CMF recurrence rate reduction is largely restricted to two specific spans. These temporally separate recurrence clusters occur during the first and third year of follow-up, while the second-year recurrences are weakly affected. (iii) Prolonging adjuvant treatment from 6 to 12 months partially alters this recurrence timing, without appreciably affecting the overall recurrence rate. (iv) These effects upon the dynamics of post-resection occurrence are menopausal status-independent.

CONCLUSIONS

At least two different therapeutically vulnerable proliferative events, resulting in clinical appearance of two metastasis temporally distinct clusters of post-resection cancer recurrence, apparently occur during the administration of adjuvant chemotherapy. Metastases that transpire outside of these temporal windows are refractory to adjuvant therapy. The dynamics of both post-treatment recurrence risk and CMF effectiveness are similar for both pre- and postmenopausal women, suggesting that post-resection mechanisms by which chemotherapy prevents metastases are similar, but of different magnitude in pre- and postmenopausal women. These findings are consistent with a metastasis model that includes tumor dormancy in specific micrometastatic phases (single cells and avascular foci) and with the acceleration of the metastatic process by the surgical resection of the primary breast cancer.

Quantitative target sizes for breast tumor detection prior to metastasis: a prerequisite to rational design of 4D scanners for breast screening

It is important to determine a breast cancer tumor target size for new screening equipment and molecular detection. Records of women aged 40-69 years diagnosed in 1988-1997 with a nonmetastasized, node-negative, or node-positive T1-stage breast cancer were abstracted from the Surveillance, Epidemiology, and End Results (SEER) public-use database. The linear, Gompertzian, lognormal, and power-exponential models of the effect of tumor size on breast cancer specific mortality were compared using corresponding transforms of size in multivariate Cox proportional hazard models. Criteria for comparison were the linearization of the size transforms and the Nagelkerke R2N index for the Cox models. Our results show that the assumption of a linear effect of tumor size was rejected by the linearity test (P=0.05). The Gompertzian, lognormal, and power-exponential transforms satisfied the test with P-values of 0.08, 0.29, and 0.14, respectively. The corresponding R2N were 0.08410, 0.08420, and 0.08414, respectively, showing a marginally best fit with the lognormal model, which was selected as a model for small tumors. The lognormal function with unadjusted crude death rates gave a lognormal-location parameter of 25 and shape parameter of 1.7, while the corresponding values in multivariate models were 18 and 2, respectively. The derivation of the lognormal model indicates tumor growth acceleration starting at 3 mm (unadjusted crude data) or 2 mm (multivariate model). The breast cancer tumor target size for screening equipment, whether by imaging or molecular detection, is therefore 2 mm.

Menopausal status dependence of the timing of breast cancer recurrence after surgical removal of the primary tumour

INTRODUCTION

Information on the metastasis process in breast cancer patients undergoing primary tumour removal may be extracted from an analysis of the timing of clinical recurrence.

METHODS

The hazard rate for local-regional and/or distant recurrence as the first event during the first 4 years after surgery was studied in 1173 patients undergoing mastectomy alone as primary treatment for operable breast cancer. Subset analyses were performed according to tumour size, axillary nodal status and menopausal status.

RESULTS

A sharp two-peaked hazard function was observed for node-positive pre-menopausal patients, whereas results from node-positive post-menopausal women always displayed a single broad peak. The first narrow peak among pre-menopausal women showed a very steep rise to a maximum about 8-10 months after mastectomy. The second peak was considerably broader, reaching its maximum at 28-30 months. Post-menopausal patients displayed a wide, nearly symmetrical peak with maximum risk at about 18-20 months. Peaks displayed increasing height with increasing axillary lymph node involvement. No multi-peaked pattern was evident for either pre-menopausal or post-menopausal node-negative patients; however, this finding should be considered cautiously because of the limited number of events. Tumour size influenced recurrence risk but not its timing. Findings resulting from the different subsets of patients were remarkably coherent and each observed peak maintained the same position on the time axis in all analysed subsets.

CONCLUSIONS

The risk of early recurrence for node positive patients is dependent on menopausal status. The amount of axillary nodal involvement and the tumour size modulate the risk value at any given time. For pre-menopausal node-positive patients, the abrupt increase of the first narrow peak of the recurrence risk suggests a triggering event that synchronises early risk. We suggest that this event is the surgical removal of the primary tumour. The later, broader, more symmetrical risk peaks indicate that some features of the corresponding metastatic development may present stochastic traits. A metastasis development model incorporating tumour dormancy in specific micro-metastatic phases, stochastic transitions between them and sudden acceleration of the metastatic process by surgery can explain these risk dynamics.

An early peak of relapse after surgery for breast cancer

There is great interest among oncologists concerning what we might learn by examining the pattern of relapse after breast cancer surgery. What you see depends upon how hard you look. Up to now, investigators have examined the hazard ratio for relapse every 6–12 months. In a research paper, published in this issue of Breast Cancer Research, the Milan group have looked at the hazard ratio every three months and have found, for the first time, a distinct, very early peak of relapse in a group of premenopausal, node-positive patients not given chemotherapy or hormone therapy. What is now needed is for other groups to repeat this observation and, if found, to examine the characteristics of the tumours producing this phenomenon in order to develop hypotheses about its cause and possible treatments.

The effects of delays in radiotherapy treatment on tumour control

There is often a considerable delay from initial tumour diagnosis to the start of radiotherapy treatment, which may be due to factors such as waiting lists and referral delays. This paper uses widely published models and clinical parameters to calculate the effect of delays in treatment on local tumour control for four different types of tumour-squamous cell carcinoma (head and neck), breast, cervix and prostate. The Poisson model for tumour control probability (TCP), an exponential function for tumour growth and the linear quadratic model of cell kill are used to calculate the change in TCP for delays between diagnosis and treatment of up to 100 days. Typical values of the clinical parameters have been taken from the literature; these include alpha and beta, sigma(alpha), tumour size at diagnosis, pre-treatment doubling time, delay in onset of accelerated repopulation and doubling time during treatment. It is acknowledged that there are limitations in the reliability of these data for predicting absolute values of tumour control, but models are still useful for predicting how changes in treatment parameters are likely to affect the outcome. It is shown that for fast-growing tumours a delay of 1-2 months can have a significant adverse effect on the outcome, whereas for slow-growing tumours such as Ca prostate a delay of a few months does not significantly reduce the probability of tumour control. These calculations show the importance of ensuring that delays from diagnosis through to treatment are minimized, especially for patients with rapidly proliferating tumours.

Cancer spread and micrometastasis development: quantitative approaches for in vivo models

Death from cancer is usually due to metastasis. Fortunately, most cells that escape from a primary tumor fail to form metastases. Identifying reasons for this failure will help development of anti-metastatic therapies. Intravital videomicroscopy (IVVM) can be used to observe cancer cells injected into live animals. Co-injected microspheres can be used to assess cell survival. These techniques have been used to show that circulating tumor cells generally arrest in the microcirculation and may extravasate with high efficiency. While many tumor cells may survive in a secondary site, only a small subset form micrometastases and only a subset of these micrometastases persist to form vascularized macrometastases. Furthermore, solitary tumor cells may remain dormant for long periods of time in secondary sites. These findings suggest that metastatic growth and angiogenesis are prime targets for anti-metastatic therapy.

Dissemination and growth of cancer cells in metastatic sites

Metastases, rather than primary tumours, are responsible for most cancer deaths. To prevent these deaths, improved ways to treat metastatic disease are needed. Blood flow and other mechanical factors influence the delivery of cancer cells to specific organs, whereas molecular interactions between the cancer cells and the new organ influence the probability that the cells will grow there. Inhibition of the growth of metastases in secondary sites offers a promising approach for cancer therapy.

Sequencing surgery, radiotherapy and chemotherapy: insights from a mathematical analysis

We present results from a mathematical analysis that is aimed at finding the best way to sequence the three traditional cancer treatments: surgery (S), chemotherapy (C), and radiotherapy (R). The mathematical model tracks the temporal evolution of the primary tumor and its associated metastases, and incorporates the primary tumor's effect on the dormancy and growth of the metastases. We show that the SCR schedule (i.e., surgery followed by chemotherapy followed by radiotherapy) achieves a higher cure probability than SRC if the primary tumor is sufficiently large or if the metastatic population is sufficiently large relative to the primary tumor. We also show that a novel schedule, SRCR, which splits the radiotherapy regimen into two disjoint portions, is optimal among all schedules, provided that the patient's dormant metastatic tumors do not become vascularized within about 40 days after surgery.

Tumour dormancy: findings and hypotheses from clinical research on breast cancer

Breast cancer metastatic development is commonly considered as resulting from continuous tumour growth from tumour seeding until clinical recurrence is documented. Continuous growth model inferences, however, fail to explain clinical findings concerning local recurrences, as well as the time-distribution of first treatment failure and mortality for patients undergoing mastectomy. The tumour dormancy hypothesis is considered to provide a more reasonable description of the natural history of breast cancer, while primary tumour removal is believed to be a potential perturbing factor for metastasis development. A new model of the natural history of operable breast cancer, incorporating tumour dormancy and starting signals from surgery for micrometastatic growth is proposed.