Adjuvant denosumab in breast cancer (ABCSG-18): a multicentre, randomised, double-blind, placebo-controlled trial

Therapeutic Bone-Modifying Agents in the Nonmetastatic Breast Cancer Setting: The Controversy and a Value Assessment

Clinical trials and meta-analyses investigating bisphosphonates as an adjuvant breast cancer therapy have shown a consistent trend, with postmenopausal women and women receiving ovarian suppression with gonadotropin-releasing hormone therapy gaining improved breast cancer outcomes with the use of adjuvant bisphosphonate therapy. The interpretation of these data is controversial, because the primary endpoints of the majority of adjuvant bisphosphonate studies have been negative. Pros and cons as well as the value of adjuvant bisphosphonate therapy are discussed here.

Management of Aromatase Inhibitor-Associated Bone Loss (AIBL) in postmenopausal women with hormone sensitive breast cancer: Joint position statement of the IOF, CABS, ECTS, IEG, ESCEO IMS, and SIOG

BACKGROUND

Several guidelines have been reported for bone-directed treatment in women with early breast cancer (EBC) for averting fractures, particularly during aromatase inhibitor (AI) therapy. Recently, a number of studies on additional fracture related risk factors, new treatment options as well as real world studies demonstrating a much higher fracture rate than suggested by randomized clinical controlled trials (RCTs). Therefore, this updated algorithm was developed to better assess fracture risk and direct treatment as a position statement of several interdisciplinary cancer and bone societies involved in the management of AI-associated bone loss (AIBL).

PATIENTS AND METHODS

A systematic literature review identified recent advances in the management of AIBL. Results with individual agents were assessed based on trial design, size, follow-up, and safety.

RESULTS

Several fracture related risk factors in patients with EBC were identified. Although, the FRAX algorithm includes fracture risk factors (RF) in addition to BMD, it does not seem to adequately address the effects of AIBL. Several antiresorptive agents can prevent and treat AIBL. However, concerns regarding compliance and long-term safety remain. Overall, the evidence for fracture prevention is strongest for denosumab 60 mg s.c. every 6 months. Additionally, recent studies as well as an individual patient data meta-analysis of all available randomized trial data support additional anticancer benefits from adjuvant bisphosphonate treatment in postmenopausal women with a 34% relative risk reduction in bone metastasis and 17% relative risk decrease in breast cancer mortality that needs to be taken into account when advising on management of AIBL.

CONCLUSIONS

In all patients initiating AI treatment, fracture risk should be assessed and recommendation with regard to exercise and calcium/vitamin D supplementation given. Bone-directed therapy should be given to all patients with a T-score<-2.0 or with a T-score of <-1.5 SD with one additional RF, or with ≥2 risk factors (without BMD) for the duration of AI treatment. Patients with T-score>-1.5 SD and no risk factors should be managed based on BMD loss during the first year and the local guidelines for postmenopausal osteoporosis. Compliance should be regularly assessed as well as BMD on treatment after 12 - 24 months. Furthermore, because of the decreased incidence of bone recurrence and breast cancer specific mortality, adjuvant bisphosphonates are recommended for all postmenopausal women at significant risk of disease recurrence.

Assessing fracture risk in early stage breast cancer patients treated with aromatase-inhibitors: An enhanced screening approach incorporating trabecular bone score

INTRODUCTION

Aromatase-inhibitors (AIs) are commonly used for treatment of patients with hormone-receptor positive breast carcinoma, and are known to induce bone density loss and increase the risk of fractures. The current standard-of-care screening tool for fracture risk is bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). The fracture risk assessment tool (FRAX®) may be used in conjunction with BMD to identify additional osteopenic patients at risk of fracture who may benefit from a bone-modifying agent (BMA). The trabecular bone score (TBS), a novel method of measuring bone microarchitecture by DXA, has been shown to be an independent indicator of increased fracture risk. We report how the addition of TBS and FRAX®, respectively, to BMD contribute to identification of elevated fracture risk (EFR) in postmenopausal breast cancer patients treated with AIs.

METHODS

100 patients with early stage hormone-positive breast cancer treated with AIs, no prior BMAs, and with serial DXAs were identified. BMD and TBS were measured from DXA images before and following initiation of AIs, and FRAX® scores were calculated from review of clinical records. EFR was defined as either: BMD ≤-2.5 or BMD between -2.5 and -1 plus either increased risk by FRAX® or degraded microstructure by TBS.

RESULTS

At baseline, BMD alone identified 4% of patients with EFR. The addition of FRAX® increased detection to 13%, whereas the combination of BMD, FRAX® and TBS identified 20% of patients with EFR. Following AIs, changes in TBS were independent of changes in BMD. On follow-up DXA, BMD alone detected an additional 1 patient at EFR (1%), whereas BMD+ FRAX® identified 3 additional patients (3%), and BMD+FRAX®+TBS identified 7 additional patients (7%).

CONCLUSIONS

The combination of FRAX®, TBS, and BMD maximized the identification of patients with EFR. TBS is a novel assessment that enhances the detection of patients who may benefit from BMAs.

Low-trauma fractures without osteoporosis

In clinical practice, areal bone mineral density (aBMD) is usually measured using dual-energy X-ray absorptiometry (DXA) to assess bone status in patients with or without osteoporotic fracture. As BMD has a Gaussian distribution, it is difficult to define a cutoff for osteoporosis diagnosis. Based on epidemiological considerations, WHO defined a DXA-based osteoporosis diagnosis with a T-score <-2.5. However, the majority of individuals who have low-trauma fractures do not have osteoporosis with DXA (i.e., T-score <-2.5), and some of them have no decreased BMD at all. Some medical conditions (spondyloarthropathies, chronic kidney disease and mineral bone disorder, diabetes, obesity) or drugs (glucocorticoids, aromatase inhibitors) are more prone to cause fractures with subnormal BMD. In the situation of fragility fractures with subnormal or normal BMD, clinicians face a difficulty as almost all the pharmacologic treatments have proved their efficacy in patients with low BMD. However, some data are available in post hoc analyses in patients with T score >-2. Overall, in patients with a previous fragility fracture (especially vertebra or hip), treatments appear to be effective. Thus, the authors recommend treating some patients with a major fragility fracture even if areal BMD T score is above -2.5.

Committee Opinion No. 663: Aromatase Inhibitors in Gynecologic Practice

Aromatase inhibitors have been used for the treatment of breast cancer, ovulation induction, endometriosis, and other estrogen-modulated conditions. For women with breast cancer, bone mineral density screening is recommended with long-term aromatase inhibitor use because of risk of osteoporosis due to estrogen deficiency. Based on long-term adverse effects and complication safety data, when compared with tamoxifen, aromatase inhibitors are associated with a reduced incidence of thrombosis, endometrial cancer, and vaginal bleeding. For women with polycystic ovary syndrome and a body mass index greater than 30, letrozole should be considered as first-line therapy for ovulation induction because of the increased live birth rate compared with clomiphene citrate. Lifestyle changes that result in weight loss should be strongly encouraged. Aromatase inhibitors are a promising therapeutic option that may be helpful for the management of endometriosis-associated pain in combination therapy with progestins.

Overcoming immunosuppression in bone metastases

Bone metastases are present in up to 70% of advanced prostate and breast cancers and occur at significant rates in a variety of other cancers. Bone metastases can be associated with significant morbidity. The establishment of bone metastasis activates several immunosuppressive mechanisms. Hence, understanding the tumor-bone microenvironment is crucial to inform the development of novel therapies. This review describes the current standard of care for patients with bone metastatic disease and novel treatment options targeting the microenvironment. Treatments reviewed include immunotherapies, cryoablation, and targeted therapies. Combinatorial treatment strategies including targeted therapies and immunotherapies show promise in pre-clinical and clinical studies to overcome the suppressive environment and improve treatment of bone metastases.

St. Gallen/Vienna 2017: A Brief Summary of the Consensus Discussion about Escalation and De-Escalation of Primary Breast Cancer Treatment

For the second time, the St. Gallen Consensus Conference on early breast cancer treatment standards took place in Vienna, Austria, where it will remain for the foreseeable future (next date: March 20-23, 2019). With the probably most prominent line-up of global breast cancer experts and more than 3,000 participants from over 100 countries, the 2017 St. Gallen/Vienna conference again was a huge success. A generation change took place with respect to the Conference Co-Chairpersons. Traditionally, the experts from all continents reviewed publications from the past 2 years, and discussed whether new diagnostic or therapeutic means were ready for routine everyday practice. This year, the conference's main theme was 'Escalating and Deescalating Treatment', and the traditional panel votings clarified a number of issues in this respect. Several subjects of all breast cancer modalities were further de-escalated (surgery: 'no ink on tumor' clearly confirmed as standard; resection within new limits after neoadjuvant systemic therapy; axillary dissection may also be avoided after mastectomy under certain circumstances; radiotherapy: hypofractionation is standard of care in breast conserving therapy; chemotherapy: can be avoided in low-risk patients). However, others were escalated: surgery: after neoadjuvant treatment and after mastectomy a positive sentinel node leads to axillary dissection; radiotherapy: regional nodes have to be irradiated in 4+ nodes situations; adjuvant therapy: bisphosphonates as standard for postmenopausal women. There was no clear panel opinion on the optimal use of multigenomic assays. As always, the panel recommendations are strictly opinion-based, and try to depict the 'usual' treatment for the 'average' patients. This rapid report by the editors-in-chief of Breast Care summarizes the results of the 2017 international panel votings with respect to loco-regional systemic treatment, and does not intend to replace the official St. Gallen Consensus publication.

Highlights from the 15th St Gallen International Breast Cancer Conference 15-18 March, 2017, Vienna: tailored treatments for patients with early breast cancer

The 15th St Gallen International Breast Cancer Conference was held in Vienna for the second time, from 15th–18th March 2017. 4000 people from 105 countries all over the world were invited to take part in the event. The real highlight of the conference was the last day with the International Consensus Session which was chaired by around 50 experts on breast cancer worldwide. With reference to data from scientific research, the consensus panel tried to offer guidelines for the management of breast cancer with the aim of providing patients with optimal treatment. The topics covered focused on the treatment of breast cancer, consideration of surgery, radiotherapy, neo-adjuvant, and adjuvant systemic therapy for breast cancer, as well as genetics and prevention of breast cancer.

In particular, in terms of precision medicine, an important topic of the conference was ‘is it possible to think that it could become routine in clinical practice to use immunotherapy and targeted therapy based on genetic signatures?’

In view of personalised therapy, it is important to take into consideration women’s treatment preferences. It is also important not only to offer guidelines which help breast cancer experts all over the world to choose the proper treatment for women with breast cancer but also to discuss the pros and cons of the therapy with the patient. This allows for a better understanding of the disease.

‘From the maximum tolerable to the minimum effective treatment: it is essential to escalate treatment when necessary and to de-escalate when unnecessary’. These few words could summarise the meaning of the 15th St Gallen International Breast Cancer Conference. Prof Martine Piccart-Gebhart was awarded with the St Gallen International Breast Cancer Award 2017 for her fundamental clinical research contribution and Prof Giuseppe Curigliano with the Umberto Veronesi Memorial Award which aims to recognise a physician’s leading role in advancing the science and care of breast cancer patients. Curigliano, in his lecture, spoke about the revolutionary immunotherapy in the clinical management of breast cancer (BC). For the development of these therapies, it is necessary to identify the genetic determinants of BC immune phenotypes in which The Cancer Genome Atlas (TCGA) has contributed towards this.

For example, the T helper (Th-1) phenotype (ICR4), which also exhibits upregulation of immune-regulatory transcripts (eg. PDL1, PD1, FOXP3, IDO1, and CTLA4), was associated with prolonged patients’ survival. Chromosome segment 4q21, which includes genes encoding the Th-1 chemokines CXCL9-11, was significantly amplified only in the immune favourable phenotype (ICR4). The mutation and neo-antigen load progressively decreased from ICR4 to ICR1 but could not explain immune phenotypic differences. Mutations of TP53 were enriched in the immune favourable phenotype (ICR4). Instead, the presence of MAP3K1 and MAP2K4 mutations were closely associated with an immune unfavourable phenotype (ICR1). Using both the TCGA and the validation dataset, the degree of MAPK deregulation segregates BC according to their immune disposition. These findings suggest that mutational-driven deregulation of MAPK pathways is linked to the negative regulation of intratumoural immune response in BC.

The main themes of this congress were: 1) Surgery of the primary tumour and margins; 2) Surgery of the axilla; 3) Radiotherapy: hypofractionated, ‘boost’ to tumour bed, partial breast, regional node, after mastectomy, advanced technology; 4) Pathology: subtypes, TILs; 5) Multi-gene signatures and therapy; 6) Endocrine therapy: pre- and post-menopausal and duration; 7) Chemotherapy: subtypes, stages; 8) Anti-HER-2 therapy; 9) Neo-adjuvant therapy; 10) Adjuvant bisphosponates; 11) Adjuvant diet and exercise.

Morphometric vertebral fractures in breast cancer patients treated with adjuvant aromatase inhibitor therapy: A cross-sectional study

BACKGROUND

The impact of long-term adjuvant therapy with aromatase inhibitors (AIs) on vertebral fracture (VF) risk is still unclear.

OBJECTIVE

In this cross-sectional study, we explored the prevalence and determinants of VFs in breast cancer (BC) patients before and during AI therapy. Each woman underwent a dual-energy X-ray absorptiometry (DXA) to evaluate bone mineral density (BMD) and identify VFs by a quantitative morphometric approach. Blood samples were collected to measure serum hormone and calcium levels.

RESULTS

We consecutively included 263 postmenopausal women with hormone receptor-positive early BC. One-hundred-sixty-nine women were AI-naïve, and 94 were AI-treated. AI-treated patients had lower BMD at total hip (p=0.01) and lumbar spine (p=0.03), higher serum vitamin D (p<0.001) and parathyroid hormone (p=0.006) values as compared to AI-naïve patients. The prevalence of VFs was 18.9% in AI-naïve patients, and 31.2% in those assessed during AI therapy (odds ratio 1.90, 95% CI 1.1-3.5, p=0.03). In AI-naïve patients, VFs were associated with older age (p=0.002) and lower BMD values at femoral neck (p=0.04) and total hip (p=0.007), whereas VFs occurred without association with any parameter analyzed in AI-treated patients. In AI-treated group, the prevalence of VFs was not significantly different between patients with osteoporosis and those with normal BMD (36.7% vs. 20.0%; p=0.31).

CONCLUSIONS

In women with early BC, AI therapy is associated with high prevalence of radiological VFs, which were shown to be independent of BMD values during the adjuvant treatment. These findings may be clinically relevant since they may lead to a change in management of AI-induced skeletal fragility. Specifically, the results of this study provide a rationale for performing a morphometric evaluation of VFs in all women undergoing treatment with AIs.

Non-autonomous cell proliferation in the mammary gland and cancer

Cells decide whether to grow and divide by integrating internal and external signals. Non-autonomous cell growth and proliferation occurs when microenvironmental signals from neighboring cells, both physical and secreted, license this decision. Understanding these processes is vital to developing an accurate framework for cell-cell interactions and cellular decision-making, and is useful for advancing new therapeutic strategies to prevent dysregulated growth. Here, we review some recent examples of non-autonomous cell growth in the mammary gland and tumor cell proliferation.

Precancer Atlas to Drive Precision Prevention Trials

Cancer development is a complex process driven by inherited and acquired molecular and cellular alterations. Prevention is the holy grail of cancer elimination, but making this a reality will take a fundamental rethinking and deep understanding of premalignant biology. In this Perspective, we propose a national concerted effort to create a Precancer Atlas (PCA), integrating multi-omics and immunity - basic tenets of the neoplastic process. The biology of neoplasia caused by germline mutations has led to paradigm-changing precision prevention efforts, including: tumor testing for mismatch repair (MMR) deficiency in Lynch syndrome establishing a new paradigm, combinatorial chemoprevention efficacy in familial adenomatous polyposis (FAP), signal of benefit from imaging-based early detection research in high-germline risk for pancreatic neoplasia, elucidating early ontogeny in BRCA1-mutation carriers leading to an international breast cancer prevention trial, and insights into the intricate germline-somatic-immunity interaction landscape. Emerging genetic and pharmacologic (metformin) disruption of mitochondrial (mt) respiration increased autophagy to prevent cancer in a Li-Fraumeni mouse model (biology reproduced in clinical pilot) and revealed profound influences of subtle changes in mt DNA background variation on obesity, aging, and cancer risk. The elaborate communication between the immune system and neoplasia includes an increasingly complex cellular microenvironment and dynamic interactions between host genetics, environmental factors, and microbes in shaping the immune response. Cancer vaccines are in early murine and clinical precancer studies, building on the recent successes of immunotherapy and HPV vaccine immune prevention. Molecular monitoring in Barrett's esophagus to avoid overdiagnosis/treatment highlights an important PCA theme. Next generation sequencing (NGS) discovered age-related clonal hematopoiesis of indeterminate potential (CHIP). Ultra-deep NGS reports over the past year have redefined the premalignant landscape remarkably identifying tiny clones in the blood of up to 95% of women in their 50s, suggesting that potentially premalignant clones are ubiquitous. Similar data from eyelid skin and peritoneal and uterine lavage fluid provide unprecedented opportunities to dissect the earliest phases of stem/progenitor clonal (and microenvironment) evolution/diversity with new single-cell and liquid biopsy technologies. Cancer mutational signatures reflect exogenous or endogenous processes imprinted over time in precursors. Accelerating the prevention of cancer will require a large-scale, longitudinal effort, leveraging diverse disciplines (from genetics, biochemistry, and immunology to mathematics, computational biology, and engineering), initiatives, technologies, and models in developing an integrated multi-omics and immunity PCA - an immense national resource to interrogate, target, and intercept events that drive oncogenesis. Cancer Res; 77(7); 1510-41. ©2017 AACR.

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Zusammenfassung. Die Senkung der Inzidenz osteoporotischer Frakturen ist eine grosse Herausforderung in den nächsten Jahrzehnten. Primärprävention, Früherkennung von Risikopatienten, Reduktion von Risikofaktoren und rechtzeitiger Behandlungsbeginn sind wirksame Massnahmen zur Vermeidung von Osteoporosefrakturen. Basis jeder Osteoporosetherapie sind Allgemeinmassnahmen, Optimierung der Ernährung, Diagnostik und Risikoanalyse sowie die Wahl des optimalen Medikamentes. Die Behandlung der Osteoporose erfordert jahrzehntelanges Management. Regelmässige Kontrolle des Therapieerfolges und die Reevaluation der Risiken der Langzeitbehandlung sind gefordert. Nebenwirkungen kommen grosse Aufmerksamkeit zu, weshalb der Druck nach Therapiepausen gross ist. Einige Patienten erleiden während eines solchen Therapieunterbruchs eine neue Fraktur. Für Hochrisikopatienten kann eventuell ein medikamentöser Substanzwechsel, nicht aber eine Pause empfohlen werden. In diesem Artikel werden die aktuellen Guidelines und Langzeitstrategien diskutiert.

A Prospective Observational Study on Effect of Short-Term Periodic Steroid Premedication on Bone Metabolism in Gastrointestinal Cancer (ESPRESSO-01)

BACKGROUND

A multicenter prospective observational study evaluated the effect of gastrointestinal cancer chemotherapy with short-term periodic steroid premedication on bone metabolism.

PATIENTS AND METHODS

Seventy-four patients undergoing chemotherapy for gastrointestinal cancer were studied. The primary endpoints were changes in bone mineral densities (BMDs) and metabolic bone turnover 16 weeks after initiation of chemotherapy. BMDs, measured by dual-energy x-ray absorptiometry, and serum cross-linked N-telopeptides of type I collagen (sNTX), and bone alkaline phosphatase (sBAP) were assessed for evaluation of bone resorption and formation, respectively.

RESULTS

In 74.3% (55/74) of the patients, BMDs were significantly reduced at 16 weeks relative to baseline. The percent changes of BMD were -1.89% (95% confidence interval [CI], -2.67% to -1.11%: p < .0001) in the lumbar spine, -2.24% (95% CI, -3.59% to -0.89%: p = .002) in the total hip, and -2.05% (95% CI, -3.11% to -0.99%: p < .0001) in the femoral neck. Although there was no significant difference in sNTX levels during 16 weeks (p = .136), there was a significant increase in sBAP levels (p = .010). Decreased BMD was significantly linked to number of chemotherapy cycles (p = .02). There were no significant correlations between changes in BMDs and the primary site of malignancy, chemotherapy regimens, total cumulative steroid dose, steroid dose intensity, and additive steroid usage.

CONCLUSION

Gastrointestinal cancer chemotherapy with periodic glucocorticoid premedication was associated with reduced BMD and increased sBAP levels, which were linked to number of chemotherapy cycles but independent of primary site, chemotherapy regimen, duration, and additive steroid usage. The Oncologist 2017;22:592-600 IMPLICATIONS FOR PRACTICE: Bone health and the management of treatment-related bone loss are important for cancer care. The present study showed that a significant decrease in bone mineral density (BMD) and an increase in serum bone alkaline phosphatase levels occurred in gastrointestinal cancer patients receiving chemotherapy, which were linked to number of chemotherapy cycles but were independent of primary site, chemotherapy regimen, total steroid dose, and steroid dose intensity. Surprisingly, it seems that the decreasing BMD levels after only 16 weeks of chemotherapy for gastrointestinal cancer were comparable to that of 12-month adjuvant aromatase inhibitor therapy for early-stage breast cancer patients.

Breast cancer

Breast cancer is one of the three most common cancers worldwide. Early breast cancer is considered potentially curable. Therapy has progressed substantially over the past years with a reduction in therapy intensity, both for locoregional and systemic therapy; avoiding overtreatment but also undertreatment has become a major focus. Therapy concepts follow a curative intent and need to be decided in a multidisciplinary setting, taking molecular subtype and locoregional tumour load into account. Primary conventional surgery is not the optimal choice for all patients any more. In triple-negative and HER2-positive early breast cancer, neoadjuvant therapy has become a commonly used option. Depending on clinical tumour subtype, therapeutic backbones include endocrine therapy, anti-HER2 targeting, and chemotherapy. In metastatic breast cancer, therapy goals are prolongation of survival and maintaining quality of life. Advances in endocrine therapies and combinations, as well as targeting of HER2, and the promise of newer targeted therapies make the prospect of long-term disease control in metastatic breast cancer an increasing reality.

Bone Density Screening in Postmenopausal Women With Early-Stage Breast Cancer Treated With Aromatase Inhibitors

PURPOSE

In postmenopausal women with breast cancer treated with aromatase inhibitors (AIs), most expert panels advise baseline bone mineral density testing with a dual-energy x-ray absorptiometry (DXA) scan repeated every 1 to 2 years. How often this recommendation is followed is unclear.

METHODS

We performed a retrospective analysis of women with stage I to III breast cancer who started AI therapy from January 1, 2008, to December 31, 2010, with follow-up through December 31, 2012, by using the SEER-Medicare database. Selection criteria included AI use for ≥ 6 months and no recent osteoporosis diagnosis or bisphosphonate use. We used multivariable logistic regression to investigate associations between patient characteristics and receipt of a baseline DXA scan. In patients who continued AI treatment, we assessed rates of follow-up scans.

RESULTS

In the sample of 2,409 patients (median age, 74 years), 51.0% received a baseline DXA scan. Demographic characteristics associated with the absence of a baseline DXA scan were older age (85 to 94 years v 67 to 69 years; odds ratio [OR], 0.62; 95% CI, 0.42 to 0.92) and black v white race (OR, 0.68; 95% CI, 0.47 to 0.97). Among patients who underwent a baseline DXA scan and continued AI for 3 years, 28.0% had a repeat DXA scan within 2 years and 65.9% within 3 years. In aggregate, of the 1,164 patients who continued with AI treatment for 3 years, only 34.5% had both a baseline and at least one DXA scan during the 3-year follow-up period.

CONCLUSION

The majority of older Medicare beneficiaries with breast cancer treated with AIs do not undergo appropriate bone mineral density evaluation.

Use of Adjuvant Bisphosphonates and Other Bone-Modifying Agents in Breast Cancer: A Cancer Care Ontario and American Society of Clinical Oncology Clinical Practice Guideline

Purpose To make recommendations regarding the use of bisphosphonates and other bone-modifying agents as adjuvant therapy for patients with breast cancer. Methods Cancer Care Ontario and ASCO convened a Working Group and Expert Panel to develop evidence-based recommendations informed by a systematic review of the literature. Results Adjuvant bisphosphonates were found to reduce bone recurrence and improve survival in postmenopausal patients with nonmetastatic breast cancer. In this guideline, postmenopausal includes patients with natural menopause or that induced by ovarian suppression or ablation. Absolute benefit is greater in patients who are at higher risk of recurrence, and almost all trials were conducted in patients who also received systemic therapy. Most studies evaluated zoledronic acid or clodronate, and data are extremely limited for other bisphosphonates. While denosumab was found to reduce fractures, long-term survival data are still required. Recommendations It is recommended that, if available, zoledronic acid (4 mg intravenously every 6 months) or clodronate (1,600 mg/d orally) be considered as adjuvant therapy for postmenopausal patients with breast cancer who are deemed candidates for adjuvant systemic therapy. Further research comparing different bone-modifying agents, doses, dosing intervals, and durations is required. Risk factors for osteonecrosis of the jaw and renal impairment should be assessed, and any pending dental or oral health problems should be dealt with prior to starting treatment. Data for adjuvant denosumab look promising but are currently insufficient to make any recommendation. Use of these agents to reduce fragility fractures in patients with low bone mineral density is beyond the scope of the guideline. Recommendations are not meant to restrict such use of bone-modifying agents in these situations. Additional information at www.asco.org/breast-cancer-adjuvant-bisphosphonates-guideline , www.asco.org/guidelineswiki , https://www.cancercareontario.ca/guidelines-advice/types-of-cancer/breast .

Extended Adjuvant Endocrine Therapy in Breast Cancer: Evidence and Update - A Review

The optimal duration and treatment strategies involving adjuvant endocrine therapy in early breast cancer remained largely undetermined. As data emerge on the various modalities of treatment in both pre- and postmenopausal groups, debates, and discussions continue. Most studies to date focused on the 5-year duration of treatment consisting of mainly tamoxifen. The Arimidex, Tamoxifen, Alone or in Combination (ATAC) study demonstrated that anastrozole is superior to tamoxifen and has become the mainstream treatment in postmenopausal women with early breast cancer, although the duration was arbitrarily set for 5 years, analogous to tamoxifen treatment. Several clinical trials, however, have emerged to support extended endocrine therapy as it becomes clear that the recurrence risk of breast cancer does not decrease beyond the initial 5 years of treatment. The advent of molecular signatures also plays an important role in the breast cancer profiling, and where available should be incorporated in the overall decision-making. Furthermore, side effects and noncompliance pose another issue in achieving an optimal treatment benefit. The decision-making as regards to extended endocrine treatment should therefore focus not only on the cancer biology alone but also include treatment side effects, assessment of risk of recurrence and patients' preference. In this review, we present an overview of the published studies to date as well as ongoing studies on the topic to better refine the options for adjuvant hormonal therapy.

Denosumab for the treatment of osteoporosis

Denosumab, a specific inhibitor of RANK ligand, is a novel therapy for postmenopausal osteoporosis and related disorders. An extensive clinical development program has evaluated the clinical efficacy and safety of denosumab with several thousand patients being followed for up to 10 years. Combined with more than six years of postmarketing experience, these studies provide substantial confidence that denosumab is a convenient and appropriate treatment for patients, including Asians, at high risk for fracture. This review will summarize the clinical development of denosumab and lessons learned since its approval for clinical use in 2010.

Adjudication of osteonecrosis of the jaw in phase III randomized controlled trials of denosumab: a systematic review

PURPOSE

Denosumab (an anti RANKL antibody) is known to be associated with an increased risk for osteonecrosis of the jaw (ONJ). Due to the variety of clinical presentation, many ONJ definitions are used. Evaluation of ONJ's frequency during phase III randomized controlled trials (RCTs) is crucial to assess benefit-risk ratio. We verified that phase III RCTs involving denosumab reported the definition of ONJ used.

METHODS

We systematically searched in Central, Medline, Cochrane, and Scopus, until 31 August 2015. We included original phase III RCTs, involving denosumab. Post hoc analysis and trial extension were excluded. Articles that did not mention ONJ in their methods or results were excluded. The primary outcome was the prevalence of a complete definition of ONJ. When no definition was provided, ONJ adjudication process was analyzed.

RESULTS

Of 313 articles found, 13 RCTs were included. A definition of ONJ was detailed in two RCTs (15%). For the remaining 11 RCTs, adjudication process was mentioned for nine. In those processes, "blinded," "expert," and "independent" were the most used words.

CONCLUSION

Most of the published phase III RCTs involving denosumab did not specify the definition of ONJ used to adjudicate events in the study. Instead of definition, non-scientific and non-reproducible expressions were used. Because the chosen definition could impact the ONJ estimated frequency, it should be mandatory to give the precise definition used in each RCT publication involving denosumab.

Should bone-targeted agents be standard of care in postmenopausal patients with early breast cancer?

The role of bone-targeted agents in the adjuvant treatment of early breast cancer has been debated for decades. A recent meta-analysis of individual patient data from 18,766 women provides compelling evidence supporting the use of these agents in postmenopausal women with early-stage breast cancer. Postmenopausal women who received a bisphosphonate had a significant reduction in breast cancer mortality (14.7 vs 18%; p = 0.002) and in overall survival (21.1 vs 23.5%; p = 0.005). Some questions remain such as; what bone-targeted agent is the best? What are the optimum doses, durations and schedules? Which patients benefit the most? The decision to include a bone-targeted agent should consider the absolute risk of distant recurrence and breast cancer mortality.

Severe Rebound-Associated Vertebral Fractures After Denosumab Discontinuation: 9 Clinical Cases Report

CONTEXT

Denosumab inhibits bone resorption, increases bone mineral density, and reduces fracture risk. Denosumab was approved for the treatment of osteoporosis and the prevention of bone loss in some oncological situations. Denosumab discontinuation is associated with a severe bone turnover rebound (BTR) and a rapid loss of bone mineral density. The clinical consequences of the BTR observed after denosumab discontinuation are not known.

CASES DESCRIPTION

We report 9 women who presented 50 rebound-associated vertebral fractures (RAVFs) after denosumab discontinuation. A broad biological and radiological assessment excluded other causes than osteoporosis. These 9 cases are unusual and disturbing for several reasons. First, all vertebral fractures (VFs) were spontaneous, and most patients had a high number of VFs (mean = 5.5) in a short period of time. Second, the fracture risk was low for most of these women. Third, their VFs occurred rapidly after last denosumab injection (9-16 months). Fourth, vertebroplasty was associated with a high number of new VFs. All the observed VFs seem to be related to denosumab discontinuation and unlikely to the underlying osteoporosis or osteopenia. We hypothesize that the severe BTR is involved in microdamage accumulation in trabecular bone and thus promotes VFs.

CONCLUSION

Studies are urgently needed to determine 1) the pathophysiological processes involved, 2) the clinical profile of patients at risk for RAVFs, and 3) the management and/or treatment regimens after denosumab discontinuation. Health authorities, physicians, and patients must be aware of this RAVF risk. Denosumab injections must be scrupulously done every 6 months but not indefinitely.

Issues in Breast Cancer Survivorship: Optimal Care, Bone Health, and Lifestyle Modifications

There are an estimated 3.1 million survivors of breast cancer in the United States. The predominant reasons for this substantially large population are that breast cancer is the most common noncutaneous malignancy among women and that 5-year survival rates after breast cancer treatment are approximately 90%. These patients have many medical considerations, including the need to monitor for disease recurrence and to manage complications of their previous cancer treatments. Most patients remain at risk indefinitely for local and systemic recurrences of their breast cancers and have an increased risk of developing contralateral new primary breast cancers. Therefore, optimizing care for this patient population is critical to the overall health care landscape in the United States. Here, we summarize survivorship care delivery and its challenges, the optimization of bone health in breast cancer survivors, and opportunities for risk reduction through lifestyle modifications.

Bone Metastases and Skeletal-Related Events in Medullary Thyroid Carcinoma

CONTEXT

Bone metastases (BM) can lead to devastating skeletal-related events (SREs) in cancer patients. Data regarding medullary thyroid carcinoma (MTC) with BM are lacking.

OBJECTIVE

We evaluated the natural history of BM and SREs in MTC patients identified by a cancer center tumor registry.

SETTING

The study was conducted at a tertiary cancer center.

PATIENTS AND MAIN OUTCOME MEASURES

We retrospectively reviewed the charts of MTC patients with BM who received care from 1991 to 2014 to characterize BM and SREs.

RESULTS

Of 1008 MTC patients treated, 188 were confirmed to have BM (19%), of whom 89% (168 of 188) had nonosseous distant metastases. Median time from MTC to BM diagnosis was 30.9 months (range 0-533 mo); 25% (45 of 180) had BM identified within 3 months of MTC diagnosis. Median follow-up after detecting BM was 1.6 years (range 0-23.2 y). Most patients (77%) had six or more BM lesions, most often affecting the spine (92%) and pelvis (69%). Many patients (90 of 188, 48%) experienced one or more SREs, most commonly radiotherapy (67 of 90, 74%) followed by pathological fracture (21 of 90, 23%). Only three patients had spinal cord compression. Patients with more than 10 BM lesions were more likely to experience SREs (odds ratio 2.4; P = .007), with no difference in 5-year mortality after MTC diagnosis between patients with (31%) and without SREs (23%) (P = .11).

CONCLUSIONS

In this large retrospective series, BM in MTC was multifocal, primarily involving the spine and pelvis, supporting screening these regions for metastases in at-risk patients. SREs were common but spinal cord compression was rare. Antiresorptive therapies in this population should be investigated further with prospective trials.

The endocrine influence on the bone microenvironment in early breast cancer

Multiple factors influence the survival of disseminated breast tumour cells (DTCs) in bone. Whereas gene signature studies have identified genes that predict a propensity of tumours to metastasise to bone, the bone environment is key in determining the fate of these tumour cells. Breast cancer cells locate to specific niches within the bone that support their survival, regulated by host factors within the bone microenvironment including bone cells, cells of the bone micro vasculature, immune cells and the extracellular matrix. Reproductive endocrine hormones that affect bone and clinical studies across the menopausal transition have provided comprehensive understanding of the changes in the bone microenvironment during this time. Menopause is characterized by a decrease in ovarian oestradiol and inhibins, with an increase in pituitary follicle-stimulating hormone and this review will focus on the role of these three hormones in determining the fate of DTCs in bone. Both in vivo and clinical data suggest that premenopausal bone is a conducive environment for growth of breast cancer cells in bone. Adjuvant cancer treatment aims to reduce the risk of tumour recurrence by affecting DTCs. Drugs targeting the bone resorbing osteoclasts, such as bisphosphonates, have therefore been evaluated in this setting. Both preclinical and adjuvant clinical studies have shown that bisphosphonates' ability to decrease tumour growth in bone is influenced by the levels of endocrine hormones, with enhanced effects in a postmenopausal bone microenvironment. The challenge is to understand the molecular mechanisms behind this phenomenon and to evaluate if alternative adjuvant bone-targeted therapies may be effective in premenopausal women.

SEOM Clinical Guideline for bone metastases from solid tumours (2016)

Bone metastases are common in many advanced solid tumours, being breast, prostate, thyroid, lung, and renal cancer the most prevalent. Bone metastases can produce skeletal-related events (SREs), defined as pathological fracture, spinal cord compression, need of bone irradiation or need of bone surgery, and hypercalcaemia. Patients with bone metastases experience pain, functional impairment and have a negative impact on their quality of life. Several imaging techniques are available for diagnosis of this disease. Bone-targeted therapies include zoledronic acid, a potent biphosfonate, and denosumab, an anti-RANKL monoclonal antibody. Both reduce the risk and/or delay the development of SREs in several types of tumours. Radium 233, an alpha-particle emitter, increases overall survival in patients with bone metastases from resistant castration prostate cancer. Multidisciplinary approach is essential and bone surgery and radiotherapy should be integrated in the treatment of bone metastases when necessary. This SEOM Guideline reviews bone metastases pathogenesis, clinical presentations, lab tests, imaging techniques for diagnosis and response assessment, bone-targeted agents, and local therapies, as radiation and surgery, and establishes recommendations for the management of patients with metastases to bone.

Risk of hospitalisation and death due to bone fractures after breast cancer: a registry-based cohort study

BACKGROUND

Bone fractures may have an impact on prognosis of breast cancer. The long-term risks of bone fracture in breast cancer patients have not been thoroughly studied.

METHODS

Poisson regression was used to investigate the incidence of hospitalisation due to bone fracture comparing women with and without breast cancer based on Swedish National registers. Cox regression was used to investigate the risk of being hospitalised with bone fracture, and subsequent risk of death, in a regional cohort of breast cancer patients.

RESULTS

For breast cancer patients, the 5-year risk of bone fracture hospitalisation was 4.8% and the 30-day risk of death following a bone fracture hospitalisation was 2.0%. Compared with the general population, breast cancer patients had incidence rate ratios of 1.25 (95% CI: 1.23-1.28) and 1.18 (95% CI: 1.14-1.22) for hospitalisation due to any bone fracture and hip fracture, respectively. These ratios remained significantly increased for 10 years. Comorbidities (Charlson Comorbidity Index ⩾1) were associated with the risk of being hospitalised with bone fracture. Women taking aromatase inhibitors were at an increased risk as compared with women taking tamoxifen (HR=1.48; 95% CI: 0.98-2.22). Breast cancer patients hospitalised for a bone fracture showed a higher risk of death (HR=1.83; 95% CI: 1.50-2.22) compared with those without bone fracture.

CONCLUSIONS

Women with a previous breast cancer diagnosis are at an increased risk of hospitalisation due to a bone fracture, particularly if they have other comorbidities.

Adjuvant endocrine therapy in women with oestrogen-receptor-positive breast cancer: how should the skeletal and vascular side effects be assessed and managed?

Adjuvant endocrine therapy provides oncological benefits in women with early oestrogen-receptor-positive breast cancer, but has adverse effects consequent to induced oestradiol deficiency. Bone loss is accelerated, predisposing to increased fracture risk. Metabolic effects include changes in lipid metabolism and body composition although effects on cardiovascular risk are still unclear. Women commencing endocrine therapy should be proactively counselled about and monitored for these and other therapy-related complications including arthralgia and vasomotor symptoms. We provide strategies for prevention and management of these adverse effects, based, where available, on randomized controlled trial evidence specific to breast cancer survivors receiving endocrine treatment.

Management of Potential Long-Term Toxicities in Breast Cancer Patients

Breast cancer is the most common non-cutaneous malignancy among women, and there are over 3 million breast cancer survivors living in the United States today. Excellent cure rates with modern therapies are associated with substantial toxicities for many women; it is important that health care providers attend to the resulting symptoms and issues to optimize quality of life in this population. In this article, we review management options for potential long term toxicities in breast cancer survivors, with a particular focus on bone health, fertility preservation, premature menopause, cardiac dysfunction, and cognitive impairment.

Molecular Mechanisms of Bone Metastasis: Which Targets Came from the Bench to the Bedside?

Bone metastases ultimately result from a complex interaction between cancer cells and bone microenvironment. However, prior to the colonization of the bone, cancer cells must succeed through a series of steps that will allow them to detach from the primary tumor, enter into circulation, recognize and adhere to specific endothelium, and overcome dormancy. We now know that as important as the metastatic cascade, tumor cells prime the secondary organ microenvironment prior to their arrival, reflecting the existence of specific metastasis-initiating cells in the primary tumor and circulating osteotropic factors. The deep comprehension of the molecular mechanisms of bone metastases may allow the future development of specific anti-tumoral therapies, but so far the approved and effective therapies for bone metastatic disease are mostly based in bone-targeted agents, like bisphosphonates, denosumab and, for prostate cancer, radium-223. Bisphosphonates and denosumab have proven to be effective in blocking bone resorption and decreasing morbidity; furthermore, in the adjuvant setting, these agents can decrease bone relapse after breast cancer surgery in postmenopausal women. In this review, we will present and discuss some examples of applied knowledge from the bench to the bed side in the field of bone metastasis.

Adjuvant systemic therapy in older women with breast cancer

Breast cancer in the elderly is an increasing clinical problem. In addition, ~60% of deaths from breast cancer occur in women aged 65 years and older. Despite this, older women with breast cancer have been underrepresented in clinical trials, and this has led to less than optimal evidence to guide their therapy. The management of elderly women with early breast cancer is a complex process that requires careful evaluation of life expectancy, comorbidities, patient values, and risks and benefits of available treatment options. This review will focus on current adjuvant systemic therapy options for older women with breast cancer, discuss the principles in the decision-making process, and define the role of endocrine therapy, chemotherapy, and targeted agents.

Italian association of clinical endocrinologists (AME) position statement: drug therapy of osteoporosis

Treatment of osteoporosis is aimed to prevent fragility fractures and to stabilize or increase bone mineral density. Several drugs with different efficacy and safety profiles are available. The long-term therapeutic strategy should be planned, and the initial treatment should be selected according to the individual site-specific fracture risk and the need to give the maximal protection when the fracture risk is highest (i.e. in the late life). The present consensus focused on the strategies for the treatment of postmenopausal osteoporosis taking into consideration all the drugs available for this purpose. A short revision of the literature about treatment of secondary osteoporosis due both to androgen deprivation therapy for prostate cancer and to aromatase inhibitors for breast cancer was also performed. Also premenopausal females and males with osteoporosis are frequently seen in endocrine settings. Finally particular attention was paid to the tailoring of treatment as well as to its duration.

RANK ligand as a potential target for breast cancer prevention in BRCA1-mutation carriers

Individuals who have mutations in the breast-cancer-susceptibility gene BRCA1 (hereafter referred to as BRCA1-mutation carriers) frequently undergo prophylactic mastectomy to minimize their risk of breast cancer. The identification of an effective prevention therapy therefore remains a 'holy grail' for the field. Precancerous BRCA1(mut/+) tissue harbors an aberrant population of luminal progenitor cells, and deregulated progesterone signaling has been implicated in BRCA1-associated oncogenesis. Coupled with the findings that tumor necrosis factor superfamily member 11 (TNFSF11; also known as RANKL) is a key paracrine effector of progesterone signaling and that RANKL and its receptor TNFRSF11A (also known as RANK) contribute to mammary tumorigenesis, we investigated a role for this pathway in the pre-neoplastic phase of BRCA1-mutation carriers. We identified two subsets of luminal progenitors (RANK(+) and RANK(-)) in histologically normal tissue of BRCA1-mutation carriers and showed that RANK(+) cells are highly proliferative, have grossly aberrant DNA repair and bear a molecular signature similar to that of basal-like breast cancer. These data suggest that RANK(+) and not RANK(-) progenitors are a key target population in these women. Inhibition of RANKL signaling by treatment with denosumab in three-dimensional breast organoids derived from pre-neoplastic BRCA1(mut/+) tissue attenuated progesterone-induced proliferation. Notably, proliferation was markedly reduced in breast biopsies from BRCA1-mutation carriers who were treated with denosumab. Furthermore, inhibition of RANKL in a Brca1-deficient mouse model substantially curtailed mammary tumorigenesis. Taken together, these findings identify a targetable pathway in a putative cell-of-origin population in BRCA1-mutation carriers and implicate RANKL blockade as a promising strategy in the prevention of breast cancer.

[Bone metastases : New aspects of pathogenesis and systemic therapy]

The occurrence of bone metastases, in particular secondary to breast and prostate cancer, represents a complex medical condition that is debilitating for affected patients. In order to provide an efficient and personalized therapy, an interdisciplinary treatment approach is mandatory; therefore, systemic pharmacological therapy represents a core element of the overall treatment concept. In terms of pathophysiology, the cancer cells cause a massive disturbance of the local bone microenvironment, which as a rule leads to activation of bone resorbing osteoclasts. In addition to bisphosphonates, which can be considered classical antiresorptive agents, the monoclonal receptor activator of nuclear factor-kappa B ligand (RANKL) antibody denosumab has been in use in clinical practice since 2011. The alpha-emitting radioisotope Alpharadin was also recently approved for the treatment of metastatic prostate cancer. This article provides a summary of the most recent knowledge on the pathogenesis of how cancer cells alter the bone microenvironment as well as a review of established and future systemic treatment options.

Assessment of bone health in breast cancer patients starting adjuvant aromatase inhibitors: A quality improvement clinical audit

Introduction

Adjuvant Aromatase Inhibitors (AIs) predispose breast cancer patients to accelerated bone loss. Guidelines recommend initial screening and follow up of bone mineral density with dual energy X-ray absorptiometry (DEXA) scan. In this audit we assessed the rate of adherence to these guidelines and introduced awareness measures to improve it.

Methods

All post-menopausal women who started upfront adjuvant AIs (letrozole in all patients) between January 2007 and December 2013 were retrospectively identified. The standard to be audited was “These patients should have a baseline DEXA scan requested within the first 3 months of starting adjuvant AIs therapy”. A 90% or more compliance was accepted as satisfactory. Corrective measures in the form of educational and awareness sessions followed by re-auditing of the practice over the subsequent 12 months were planned in case of lower compliance rate.

Results

Three hundred and sixty seven eligible patients were identified. Baseline DEXA scan was performed in 188 (51.2%) patients. As planned, this result triggered the conduction of 4 consecutive educational sessions over a period of 2 weeks. Re-auditing the practice in the pre-defined subsequent subjects showed compliance in 47/52 (90.4%) patients.

Conclusion

This study of a sizable cohort confirms previous observations that adherence to skeletal health guidelines in this patient population is less than adequate. Adherence is improved dramatically by raising the awareness of relevant physicians.

Bone targeted therapy for preventing skeletal-related events in metastatic breast cancer

Cancer cells can alter physiological mechanisms within bone resulting in high bone turnover, and consequently in skeletal-related events (SREs), causing severe morbidity in affected patients. The goals of bone targeted therapy, as bisphosphonates and denosumab, are the reduction of incidence and the delay in occurrence of the SREs, to improve quality of life and pain control. The toxicity profile is similar between bisphosphonates and denosumab, even if pyrexia, bone pain, arthralgia, renal failure and hypercalcemia are more common with bisphosphonates, while hypocalcemia and toothache are more frequently reported with denosumab. Osteonecrosis of the jaw (ONJ) occurred infrequently without statistically significant difference. The present review aims to provide an assessment on bone targeted therapies for preventing the occurrence of SREs in bone metastatic breast cancer patients, critically analyzing the evidence available so far on their effectiveness, in light of the different mechanisms of action. Thus, we try to provide tools for the most fitting treatment of bone metastatic breast cancer patients. We also provide an overview on the usefulness of bone turnover markers in clinical practice and new molecules currently under study for the treatment of bone metastatic disease.

Bone metastasis: the importance of the neighbourhood

During the past decade preclinical studies have defined many of the mechanisms used by tumours to hijack the skeleton and promote bone metastasis. This has led to the development and widespread clinical use of bone-targeted drugs to prevent skeletal-related events. This understanding has also identified a critical dependency between colonizing tumour cells and the cells of bone. This is particularly important when tumour cells first arrive in bone, adapt to their new microenvironment and enter a long-lived dormant state. In this Review, we discuss the role of different bone cell types in supporting disseminated tumour cell dormancy and reactivation, and highlight the new opportunities this provides for targeting the bone microenvironment to control dormancy and bone metastasis.

Rebound-associated vertebral fractures after discontinuation of denosumab-from clinic and biomechanics

Rebound-associated vertebral fractures may follow treatment discontinuation of highly potent reversible bone antiresorptives, resulting from the synergy of rapid bone resorption and accelerated microdamage accumulation in trabecular bone.

INTRODUCTION

The purposes of this study are to characterize rebound-associated vertebral fractures following the discontinuation of a highly potent reversible antiresorptive therapy based on clinical observation and propose a pathophysiological rationale.

METHODS

This study is a case report of multiple vertebral fractures early after discontinuation of denosumab therapy in a patient with hormone receptor-positive non-metastatic breast cancer treated with an aromatase inhibitor.

RESULTS

Discontinuation of highly potent reversible bone antiresorptives such as denosumab may expose patients to an increased fracture risk due to the joined effects of absent microdamage repair during therapy followed by synchronous excess activation of multiple bone remodelling units at the time of loss-of-effect. We suggest the term rebound-associated vertebral fractures (RVF) for this phenomenon characterized by the presence of multiple new clinical vertebral fractures, associated with either no or low trauma, in a context consistent with the presence of high bone turnover and rapid loss of lumbar spine bone mineral density (BMD) occurring within 3 to 12 months after discontinuation (loss-of-effect) of a reversible antiresorptive therapy in the absence of secondary causes of bone loss or fractures. Unlike atypical femoral fractures that emerge from failure of microdamage repair in cortical bone with long-term antiresorptive treatment, RVF originate from the synergy of rapid bone resorption and accelerated microdamage accumulation in trabecular bone triggered by the discontinuation of highly potent reversible antiresorptives.

CONCLUSIONS

Studies are urgently needed to i) prove the underlying pathophysiological processes suggested above, ii) establish the predictive criteria exposing patients to an increased risk of RVF, and iii) determine appropriate treatment regimens to be applied in such patients.

Metastatic colonization by circulating tumour cells

Metastasis is the main cause of death in people with cancer. To colonize distant organs, circulating tumour cells must overcome many obstacles through mechanisms that we are only now starting to understand. These include infiltrating distant tissue, evading immune defences, adapting to supportive niches, surviving as latent tumour-initiating seeds and eventually breaking out to replace the host tissue. They make metastasis a highly inefficient process. However, once metastases have been established, current treatments frequently fail to provide durable responses. An improved understanding of the mechanistic determinants of such colonization is needed to better prevent and treat metastatic cancer.