Molecular and Biological Mechanisms of Bone Metastasis

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

Artificial intelligence in skeletal metastasis imaging

In the field of metastatic skeletal oncology imaging, the role of artificial intelligence (AI) is becoming more prominent. Bone metastasis typically indicates the terminal stage of various malignant neoplasms. Once identified, it necessitates a comprehensive revision of the initial treatment regime, and palliative care is often the only resort. Given the gravity of the condition, the diagnosis of bone metastasis should be approached with utmost caution. AI techniques are being evaluated for their efficacy in a range of tasks within medical imaging, including object detection, disease classification, region segmentation, and prognosis prediction in medical imaging. These methods offer a standardized solution to the frequently subjective challenge of image interpretation.This subjectivity is most desirable in bone metastasis imaging. This review describes the basic imaging modalities of bone metastasis imaging, along with the recent developments and current applications of AI in the respective imaging studies. These concrete examples emphasize the importance of using computer-aided systems in the clinical setting. The review culminates with an examination of the current limitations and prospects of AI in the realm of bone metastasis imaging. To establish the credibility of AI in this domain, further research efforts are required to enhance the reproducibility and attain robust level of empirical support.

Ranking the Orthopedic Procedures With the Highest Morbidity and Mortality

BACKGROUND

Musculoskeletal conditions currently affect more than one-third of the US population and orthopedic procedures play a pivotal role in managing them. Like any invasive intervention, these carry a wide spectrum of risk, necessitating a comprehensive understanding of the associated morbidity and mortality. This study sought to provide a global perspective of the risks and complications associated with these procedures to establish an easy to understand risk stratification tool for both patients and providers.

MATERIALS AND METHODS

Current Procedural Terminology codes associated with orthopedic surgery were identified in the American College of Surgeons National Surgical Quality Improvement Program database from 2018 to 2020. Each code was associated with its rate of 30-day mortality as well as any adverse event (AAE) and then ranked for descriptive analysis.

RESULTS

In total, there were 698,549 patients who underwent orthopedic procedures associated with 94 CPT codes with at least 1 morbidity event and 144 CPT codes with at least 1 AAE. The CPT code associated with the highest mortality was 27590 or above knee amputation. The CPT code associated with the highest rate of AAE was 27507 or open treatment of femoral shaft fracture with plate and screws.

CONCLUSION

This is the first study to compare the rates of morbidity and mortality in all patients with orthopedic procedures. There was a strong bias toward increased risk associated with lower extremity surgery and surgery most often performed in the geriatric population. [Orthopedics. 202x;4x(x):xx-xx.].

Oncologic Applications of Artificial Intelligence and Deep Learning Methods in CT Spine Imaging-A Systematic Review

In spinal oncology, integrating deep learning with computed tomography (CT) imaging has shown promise in enhancing diagnostic accuracy, treatment planning, and patient outcomes. This systematic review synthesizes evidence on artificial intelligence (AI) applications in CT imaging for spinal tumors. A PRISMA-guided search identified 33 studies: 12 (36.4%) focused on detecting spinal malignancies, 11 (33.3%) on classification, 6 (18.2%) on prognostication, 3 (9.1%) on treatment planning, and 1 (3.0%) on both detection and classification. Of the classification studies, 7 (21.2%) used machine learning to distinguish between benign and malignant lesions, 3 (9.1%) evaluated tumor stage or grade, and 2 (6.1%) employed radiomics for biomarker classification. Prognostic studies included three (9.1%) that predicted complications such as pathological fractures and three (9.1%) that predicted treatment outcomes. AI's potential for improving workflow efficiency, aiding decision-making, and reducing complications is discussed, along with its limitations in generalizability, interpretability, and clinical integration. Future directions for AI in spinal oncology are also explored. In conclusion, while AI technologies in CT imaging are promising, further research is necessary to validate their clinical effectiveness and optimize their integration into routine practice.

Emerging Medical Technologies and Their Use in Bionic Repair and Human Augmentation

As both the proportion of older people and the length of life increases globally, a rise in age-related degenerative diseases, disability, and prolonged dependency is projected. However, more sophisticated biomedical materials, as well as an improved understanding of human disease, is forecast to revolutionize the diagnosis and treatment of conditions ranging from osteoarthritis to Alzheimer's disease as well as impact disease prevention. Another, albeit quieter, revolution is also taking place within society: human augmentation. In this context, humans seek to improve themselves, metamorphosing through self-discipline or more recently, through use of emerging medical technologies, with the goal of transcending aging and mortality. In this review, and in the pursuit of improved medical care following aging, disease, disability, or injury, we first highlight cutting-edge and emerging materials-based neuroprosthetic technologies designed to restore limb or organ function. We highlight the potential for these technologies to be utilized to augment human performance beyond the range of natural performance. We discuss and explore the growing social movement of human augmentation and the idea that it is possible and desirable to use emerging technologies to push the boundaries of what it means to be a healthy human into the realm of superhuman performance and intelligence. This potential future capability is contrasted with limitations in the right-to-repair legislation, which may create challenges for patients. Now is the time for continued discussion of the ethical strategies for research, implementation, and long-term device sustainability or repair.

Surgical Outcomes and Complications of Custom-Made Prostheses in Upper Limb Oncological Reconstruction: A Systematic Review

Bone tumors of the upper limb are a common cause of bone pain and pathological fractures in both old and young populations. Surgical reconstruction and limb salvage have become valid options for these patients despite this kind of surgery being challenging due to the need for wide bone resection and the involvement of surrounding soft tissues. Computer-assisted technology helps the surgeon in pre-operative planning and in designing customized implants. The aim of this study was to investigate the surgical outcomes and complications of custom-made prostheses in oncologic reconstruction of the upper limb and if they are reliable options for patients suffering from aggressive tumors. An electronic search on PubMed, Google Scholar, and Web of Knowledge was conducted to identify all available articles on the use of custom-made prostheses in oncological resections of the upper limb. Twenty-one studies were included in the review, comprising a total of 145 patients with a mean age of 33.68 years. The bone involved was the humerus in 93 patients, and the radius was involved in 36 patients. There were only six cases involving proximal ulna, three cases involving the scapula, and seven cases involving the elbow as well as soft tissues around it. The most frequent primary tumor was the giant cell tumor, with 36 cases, followed by osteosarcoma with 25 cases, Ewing Sarcoma with 17 cases, and Chondrosarcoma with 7 total cases. Forty patients were affected by bone metastases (such as renal cell cancer, breast cancer, melanoma, and rectal cancer) or hematologic diseases involving bone (lymphoma, myeloma, or non-Hodgkin disease). Custom-made prostheses are a viable option for patients who suffer from malignant tumors in their upper limbs. They are a reliable aid for surgeons in cases of extensive resections.

The Use of Microspheres for Cancer Embolization Therapy: Recent Advancements and Prospective

Embolization therapy involving biomaterials has improved the therapeutic strategy for most liver cancer treatments. Developing biomaterials as embolic agents has significantly improved patients' survival rates. Various embolic agents are present in liquid agents, foam, particulates, and particles. Some of the most applied embolic agents are microparticles, such as microspheres (3D micrometer-sized spherical particles). Microspheres with added functionalities are currently being developed for effective therapeutic embolization. Their excellent properties of high surface area and capacity for being loaded with radionuclides and alternate active or therapeutic agents provide an additional advantage to overcome limitations from traditional cancer treatments. Microspheres (non-radioactive and radioactive) have been widely used and explored for localized cancer treatment. Non-radioactive microspheres exhibit improved clinical performance as drug delivery vehicles in chemotherapy due to their controlled and sustained drug release to the target site. They offer better flow properties and are beneficial for the ease of delivery via injection procedures. In addition, radioactive microspheres have also been exploited for use as an embolic platform in internal radiotherapy as an alternative to cancer treatment. This short review summarizes the progressive development of non-radioactive and radioactive embolic microspheres, emphasizing material characteristics. The use of embolic microspheres for various modalities of therapeutic arterial embolization and their impact on therapeutic performance are also discussed.

Beyond boundaries: unraveling innovative approaches to combat bone-metastatic cancers

Evidence demonstrated that bones, liver, and lungs are the most common metastasis sites in some human malignancies, especially in prostate and breast cancers. Bone is the third most frequent target for spreading tumor cells among these organs and tissues. Patients with bone-metastatic cancers face a grim prognosis characterized by short median survival time. Current treatments have proven insufficient, as they can only inhibit metastasis or tumor progression within the bone tissues rather than providing a curative solution. Gaining a more profound comprehension of the interplay between tumor cells and the bone microenvironment (BME) is of utmost importance in tackling this issue. This knowledge will pave the way for developing innovative diagnostic and therapeutic approaches. This review summarizes the mechanisms underlying bone metastasis and discusses the clinical aspects of this pathologic condition. Additionally, it highlights emerging therapeutic interventions aimed at enhancing the quality of life for patients affected by bone-metastatic cancers. By synthesizing current research, this review seeks to shed light on the complexities of bone metastasis and offer insights for future advancements in patient care.

The British Orthopaedic Oncology Management (BOOM) audit

Aims

Most patients with advanced malignancy suffer bone metastases, which pose a significant challenge to orthopaedic services and burden to the health economy. This study aimed to assess adherence to the British Orthopaedic Oncology Society (BOOS)/British Orthopaedic Association (BOA) guidelines on patients with metastatic bone disease (MBD) in the UK.

Methods

A prospective, multicentre, national collaborative audit was designed and delivered by a trainee-led collaborative group. Data were collected over three months (1 April 2021 to 30 June 2021) for all patients presenting with MBD. A data collection tool allowed investigators at each hospital to compare practice against guidelines. Data were collated and analyzed centrally to quantify compliance from 84 hospitals in the UK for a total of 1,137 patients who were eligible for inclusion.

Results

A total of 846 patients with pelvic and appendicular MBD were analyzed, after excluding those with only spinal metastatic disease. A designated MBD lead was not present in 39% of centres (33/84). Adequate radiographs were not performed in 19% of patients (160/846), and 29% (247/846) did not have an up-to-date CT of thorax, abdomen, and pelvis to stage their disease. Compliance was low obtaining an oncological opinion (69%; 584/846) and prognosis estimations (38%; 223/846). Surgery was performed in 38% of patients (319/846), with the rates of up-to-date radiological investigations and oncology input with prognosis below the expected standard. Of the 25% (215/846) presenting with a solitary metastasis, a tertiary opinion from a MBD centre and biopsy was sought in 60% (130/215).

Conclusion

Current practice in the UK does not comply with national guidelines, especially regarding investigations prior to surgery and for patients with solitary metastases. This study highlights the need for investment and improvement in care. The recent publication of British Orthopaedic Association Standards for Trauma (BOAST) defines auditable standards to drive these improvements for this vulnerable patient group.

Comparison of 99m Tc-methylenediphosphonate and 68 Ga-BPAMD PET/computed tomography imaging in bone metastasis

OBJECTIVE

Bone is considered as the third most common site of metastases, besides lung and liver. Early detection of skeletal metastases aids in better management of skeletal-related events. In the present study cold kit-based 2,2 ' ,2 '' -(10-(2-((diphosphonomethyl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (BPAMD) was labeled with 68 Ga. The radiolabeling parameters and clinical evaluation in patients with suspected bone metastases were compared with routinely used 99m Tc-methylenediphosphonate ( 99m Tc-MDP).

METHODOLOGY

The kit components of MDP were incubated with at room temperature for 10 min, followed by radiochemical purity testing using thin-layer chromatography. For radiolabeling of BPAMD, the cold kit components reconstituted in 400 μL of HPLC grade water were transferred and incubated with 68 GaCl 3 in the reactor vessel of the fluidic module at 95°C for 20 min. Radiochemical yield and purity were determined with instant thin-layer chromatography using 0.5 M sodium citrate as mobile phase. For clinical evaluation, patients ( n  = 10) with suspected bone metastases were enrolled. 99m Tc-MDP and 68 Ga-BPAMD scans were performed on two different days in random order. Imaging outcomes were noted and compared.

RESULTS

Radiolabeling of both tracers is facile using cold kit, although BPAMD requires heating. The radiochemical purity was observed to be greater than 99% for all preparations. Both MDP and BPAMD detected skeletal lesions; however, additional lesions were detected in total of seven patients which were not visualized clearly on 99m Tc-MDP scan.

CONCLUSION

BPAMD can be easily tagged with 68 Ga using cold kits. The radiotracer is suitable and efficient for detection of bone metastases using PET/computed tomography.

Evaluation of denosumab in adult oncology patients for the prevention of skeletal related events across a large academic health system

INTRODUCTION

Denosumab (Xgeva^®) and zoledronic acid (Zometa^®) are widely utilized for prevention of skeletal related events (SREs) in oncology patients. Drug costs, renal function, ease and logistics of administration, and adverse effect profile are factors frequently considered by patients and/or providers when selecting an optimal agent. Given the significantly higher drug cost of denosumab compared to zoledronic acid, an evaluation of our institution's denosumab use and investigation into opportunities to shift denosumab administrations to zoledronic acid and/or to lower cost sites-of-care was warranted.

METHODS

A single-center, multi-site, retrospective, observational analysis of the electronic medical record (EMR) was conducted for adult oncology patients who received denosumab 120 mg for prevention of SREs from October 1st, 2018 to September 30th, 2019 at three institutions within our health system. Additional information was collected to characterize the patient population based on cancer diagnosis, renal function, and concomitant calcium and vitamin D supplementation. Our primary objective was to evaluate if the use of denosumab met current formulary restrictions of the health system.

RESULTS

In total, 304 adult oncology patients received 1411 doses of denosumab for the prevention of SREs. The majority of reviewed patients had a primary oncology diagnosis of breast (35%) or lung (24%) cancer. Of the patients who received denosumab, 278 (93%) met the health system's current formulary restrictions. The majority of patients who did not meet formulary restrictions were those with multiple myeloma (MM) (20/22; 91%). Of the 304 patients reviewed, 70 had the appropriate parameters in the EMR to calculate creatinine clearance (CrCl) using Cockcroft-Gault Equation. Of those 70 patients, 59 (84%) would have been eligible to receive zoledronic acid instead of denosumab given that their CrCl >30 mL/min with no documented intolerance to bisphosphonates. Concurrent use of calcium and vitamin D is recommended when using denosumab. Based on the most recent prior to admission (PTA) medication list obtained from the 304 patients evaluated, 222 (73%) had both calcium and vitamin D listed as "taking".

CONCLUSIONS

Within our health system, denosumab is restricted to those who meet formulary restrictions. Additional education is recommended to help limit the use of denosumab, specifically in MM, to reduce drug costs when zoledronic acid is also an appropriate first-line agent.

The link between bone-derived factors osteocalcin, fibroblast growth factor 23, sclerostin, lipocalin 2 and tumor bone metastasis

The skeleton is the third most common site of metastatic disease, which causes serious bone complications and short-term prognosis in cancer patients. Prostate and breast cancers are responsible for the majority of bone metastasis, resulting in osteolytic or osteoblastic lesions. The crosstalk between bone cells and their interactions with tumor cells are important in the development of lesions. Recently, both preclinical and clinical studies documented the clinical relevance of bone-derived factors, including osteocalcin (OC) and its undercarboxylated form (ucOC), fibroblast growth factor 23 (FGF23), sclerostin (SCL), and lipocalin 2 (LCN2) as prognostic tumor biomarkers and potential therapeutic targets in bone metastasis. Both OC and ucOC could be useful targets for the prevention of bone metastasis in breast cancer. Moreover, elevated OC level may be a metastatic marker of prostate cancer. FGF23 is particularly important for those forms of cancer that primarily affect bone and/or are characterized by bone metastasis. In other tumor entities, increased FGF23 level is enigmatic. SCL plays a significant role in the pathogenesis of both osteolytic and osteoblastic lesions, as its levels are high in metastatic breast and prostate cancers. Elevated expression levels of LCN2 have been found in aggressive subtypes of cancer. However, its role in anti-metastasis varies significantly between different cancer types. Anyway, all aforementioned bone-derived factors can be used as promising tumor biomarkers. As metastatic bone disease is generally not curable, targeting bone factors represents a new trend in the prevention of bone metastasis and patient care.

Application of Artificial Intelligence Methods for Imaging of Spinal Metastasis

Spinal metastasis is the most common malignant disease of the spine. Recently, major advances in machine learning and artificial intelligence technology have led to their increased use in oncological imaging. The purpose of this study is to review and summarise the present evidence for artificial intelligence applications in the detection, classification and management of spinal metastasis, along with their potential integration into clinical practice. A systematic, detailed search of the main electronic medical databases was undertaken in concordance with the PRISMA guidelines. A total of 30 articles were retrieved from the database and reviewed. Key findings of current AI applications were compiled and summarised. The main clinical applications of AI techniques include image processing, diagnosis, decision support, treatment assistance and prognostic outcomes. In the realm of spinal oncology, artificial intelligence technologies have achieved relatively good performance and hold immense potential to aid clinicians, including enhancing work efficiency and reducing adverse events. Further research is required to validate the clinical performance of the AI tools and facilitate their integration into routine clinical practice.

Modelling skeletal pain harnessing tissue engineering

Bone pain typically occurs immediately following skeletal damage with mechanical distortion or rupture of nociceptive fibres. The pain mechanism is also associated with chronic pain conditions where the healing process is impaired. Any load impacting on the area of the fractured bone will stimulate the nociceptive response, necessitating rapid clinical intervention to relieve pain associated with the bone damage and appropriate mitigation of any processes involved with the loss of bone mass, muscle, and mobility and to prevent death. The following review has examined the mechanisms of pain associated with trauma or cancer-related skeletal damage focusing on new approaches for the development of innovative therapeutic interventions. In particular, the review highlights tissue engineering approaches that offer considerable promise in the application of functional biomimetic fabrication of bone and nerve tissues. The strategic combination of bone and nerve tissue engineered models provides significant potential to develop a new class of in vitro platforms, capable of replacing in vivo models and testing the safety and efficacy of novel drug treatments aimed at the resolution of bone-associated pain. To date, the field of bone pain research has centred on animal models, with a paucity of data correlating to the human physiological response. This review explores the evident gap in pain drug development research and suggests a step change in approach to harness tissue engineering technologies to recapitulate the complex pathophysiological environment of the damaged bone tissue enabling evaluation of the associated pain-mimicking mechanism with significant therapeutic potential therein for improved patient quality of life.

Graphical abstract

Rationale underlying novel drug testing platform development. Pain detected by the central nervous system and following bone fracture cannot be treated or exclusively alleviated using standardised methods. The pain mechanism and specificity/efficacy of pain reduction drugs remain poorly understood. In vivo and ex vivo models are not yet able to recapitulate the various pain events associated with skeletal damage. In vitro models are currently limited by their inability to fully mimic the complex physiological mechanisms at play between nervous and skeletal tissue and any disruption in pathological states. Robust innovative tissue engineering models are needed to better understand pain events and to investigate therapeutic regimes.

Severe and refractory hypocalcaemia secondary to osteoblastic bone metastases in bladder signet ring carcinoma: A case report and literature review

RATIONALE

Symptomatic hypocalcaemia is uncommon, occurring in <2% of patients with malignancy. Osteoblastic bone metastasis as a cause of hypocalcaemia is rare and not reported in bladder cancer.

PATIENT CONCERNS

We report a case of refractory hypocalcaemia in a patient with bladder cancer with extensive osteoblastic bone metastases. A 64-year-old male with a history of signet ring bladder carcinoma with osteoblastic bone metastases presented with severe hypocalcaemia with corrected calcium of 1.64 (2.09-2.46) mmol/L as well as hypomagnesemia and hypophosphatemia. He was previously treated with chemotherapy and immunotherapy. Denosumab was also initiated for the prevention of skeletal-related events.

DIAGNOSES

Additional investigations showed significantly elevated bone formation markers N-terminal propeptide of type I procollagen and alkaline phosphatase. Chest radiography and computed tomography scan also demonstrated extensive areas of sclerotic bone lesions suggestive of osteoblastic bone metastases. He was diagnosed with severe hypocalcaemia secondary to osteoblastic bone metastases and partly to denosumab, vitamin D deficiency, and hypomagnesemia.

INTERVENTIONS

He was treated aggressively with calcium and vitamin D replacement.

OUTCOMES

Despite prolonged intravenous calcium replacement and high doses of oral calcium, cholecalciferol, and calcitriol replacement, he had persistent hypocalcaemia with calcium levels ranging from 1.8 to 1.9 mmol/L. He died 4 months after his admission.

LESSONS

Osteoblastic bone metastases lead to an increased influx of calcium and phosphate into the bone leading to hypocalcaemia and should be considered as a differential in severe and refractory hypocalcaemia. It is rare and has not been described in bladder cancer. Precaution should be taken upon the initiation of antiresorptive in patients with osteoblastic bone metastases.

The Genetic Evolution of Metastasis

Cancer is an evolutionary process that is characterized by the emergence of multiple genetically distinct populations or clones within the primary tumor. Intratumor heterogeneity provides a substrate for the selection of adaptive clones, such as those that lead to metastasis. Comparative molecular studies of primary tumors and metastases have identified distinct genomic features associated with the development of metastases. In this review, we discuss how these insights could inform clinical decision-making and uncover rational antimetastasis treatment strategies.

Clinical Evaluation of an Auto-Segmentation Tool for Spine SBRT Treatment

Purpose

Spine SBRT target delineation is time-consuming due to the complex bone structure. Recently, Elements SmartBrush Spine (ESS) was developed by Brainlab to automatically generate a clinical target volume (CTV) based on gross tumor volume (GTV). The aim of this project is to evaluate the accuracy and efficiency of ESS auto-segmentation.

Methods

Twenty spine SBRT patients with 21 target sites treated at our institution were used for this retrospective comparison study. Planning CT/MRI images and physician-drawn GTVs were inputs for ESS. ESS can automatically segment the vertebra, split the vertebra into 6 sectors, and generate a CTV based on the GTV location, according to the International Spine Radiosurgery Consortium (ISRC) Consensus guidelines. The auto-segmented CTV can be edited by including/excluding sectors of the vertebra, if necessary. The ESS-generated CTV contour was then compared to the clinically used CTV using qualitative and quantitative methods. The CTV contours were compared using visual assessment by the clinicians, relative volume differences (RVD), distance of center of mass (DCM), and three other common contour similarity measurements such as dice similarity coefficient (DICE), Hausdorff distance (HD), and 95% Hausdorff distance (HD95).

Results

Qualitatively, the study showed that ESS can segment vertebra more accurately and consistently than humans at normal curvature conditions. The accuracy of CTV delineation can be improved significantly if the auto-segmentation is used as the first step. Conversely, ESS may mistakenly split or join different vertebrae when large curvatures in anatomy exist. In this study, human interactions were needed in 7 of 21 cases to generate the final CTVs by including/excluding sectors of the vertebra. In 90% of cases, the RVD were within ±15%. The RVD, DCM, DICE, HD, and HD95 for the 21 cases were 3% ± 12%, 1.9 ± 1.5 mm, 0.86 ± 0.06, 13.34 ± 7.47 mm, and 4.67 ± 2.21 mm, respectively.

Conclusion

ESS can auto-segment a CTV quickly and accurately and has a good agreement with clinically used CTV. Inter-person variation and contouring time can be reduced with ESS. Physician editing is needed for some occasions. Our study supports the idea of using ESS as the first step for spine SBRT target delineation to improve the contouring consistency as well as to reduce the contouring time.

Application of additively manufactured 3D scaffolds for bone cancer treatment: a review

Bone cancer is a critical health problem on a global scale, and the associated huge clinical and economic burdens are still rising. Although many clinical approaches are currently used for bone cancer treatment, these methods usually affect the normal body functions and thus present significant limitations. Meanwhile, advanced materials and additive manufacturing have opened up promising avenues for the development of new strategies targeting both bone cancer treatment and post-treatment bone regeneration. This paper presents a comprehensive review of bone cancer and its current treatment methods, particularly focusing on a number of advanced strategies such as scaffolds based on advanced functional materials, drug-loaded scaffolds, and scaffolds for photothermal/magnetothermal therapy. Finally, the main research challenges and future perspectives are elaborated.

Response assessment after stereotactic body radiation therapy for spine and non-spine bone metastases: results from a single institutional study

Background

The use of stereotactic body radiation therapy (SBRT) for tumor and pain control in patients with bone metastases is increasing. We report response assessment after bone SBRT using radiological changes through time and clinical examination of patients.

Methods

We analyzed retrospectively oligo-metastatic/progressive patients with bony lesions treated with SBRT between 12/2008 and 10/2018, without in-field re-irradiation, in our institution. Radiological data were obtained from imaging modalities used for SBRT planning and follow-up purposes in picture archiving and communication system and assessed by two independent radiologists blind to the time of treatment. Several radiological changes were described. Radiographic response assessment was classified according to University of Texas MD Anderson Cancer Center criteria. Pain response and the neurological deficit were captured before and at least 6 months after SBRT.

Results

A total of 35 of the 74 reviewed patients were eligible, presenting 43 bone metastases, with 51.2% (n = 22) located in the vertebral column. Median age at the time of SBRT was 66 years (range 38–84) and 77.1% (n = 27) were male. Histology was mainly prostate (51.4%, n = 18) and breast cancer (14.3%, n = 5). Median total radiation dose delivered was 24 Gy (range 24–42), in three fractions (range 2–7), prescribed to 70–90% isodose-line. After a median follow-up of 1.8 years (range < 1–8.2) for survivors, complete or partial response, stable, and progressive disease occurred in 0%, 11.4% (n = 4), 68.6% (n = 24), and 20.0% (n = 7) of the patients, respectively. Twenty patients (57.1%) died during the follow-up time, all from disease progression, yet 70% (n = 14) from this population with local stable disease after SBRT. From patients who were symptomatic and available for follow-up, almost half (44.4%) reported pain reduction after SBRT.

Conclusions

Eighty percent of the patients showed local control after SBRT for bone metastases. Pain response was favorable. For more accurate response assessment, comparing current imaging modalities with advanced imaging techniques such as functional MRI and PET/CT, in a prospective and standardized way is warranted.

Trial registration Retrospectively registered.

Mutual Modulation Between Extracellular Vesicles and Mechanoenvironment in Bone Tumors

The bone microenvironment homeostasis is guaranteed by the balanced and fine regulated bone matrix remodeling process. This equilibrium can be disrupted by cancer cells developed in the bone (primary bone cancers) or deriving from other tissues (bone metastatic lesions), through a mechanism by which they interfere with bone cells activities and alter the microenvironment both biochemically and mechanically. Among the factors secreted by cancer cells and by cancer-conditioned bone cells, extracellular vesicles (EVs) are described to exert pivotal roles in the establishment and the progression of bone cancers, by conveying tumorigenic signals targeting and transforming normal cells. Doing this, EVs are also responsible in modulating the production of proteins involved in regulating matrix stiffness and/or mechanotransduction process, thereby altering the bone mechanoenvironment. In turn, bone and cancer cells respond to deregulated matrix stiffness by modifying EV production and content, fueling the vicious cycle established in tumors. Here, we summarized the relationship between EVs and the mechanoenvironment during tumoral progression, with the final aim to provide some innovative perspectives in counteracting bone cancers.

Factors Affecting Life Expectancy After Bone Metastasis in Adults - Results of a 5-year Prospective Study

There is a scarcity of literature available regarding the factors affecting life expectancy in bone metastasis (BM). Our objective is to evaluate the factors affecting life expectancy in adult patients with BM. In this prospective cohort study for over 5 years, 111 adults with BM were included in the analysis. The life expectancy was calculated from the time of diagnosis of BM to death. Statistical analysis was done using the SPSS statistical program. The Pearson chi-square test was used to analyze the significance and life expectancy was represented on the Kaplan Meier curve. The overall median survival time was 9 months. The patients with a primary malignancy detected along with BM had a median survival of 9 months. Those without a known primary at the time of diagnosis survived for a median period of 8 months and those with known primary for 14 months (P-value 0.01). The median survival of patients with BM from the lung, breast, and prostate was 6, 14, and 24 months, respectively (P-value 0.001). Only 22% of patients with extraskeletal metastasis in addition to BM survived more than 6 months (P-value 0.013). Patients with neurological deficits had a median survival of 2 months (P-value 0.0001). There was no statistically significant association between gender and the mode of treatment and survival. There was a significant association between life expectancy and mode of presentation, the primary site of origin, presence of extraskeletal secondary, BM with unknown primary, and symptoms on presentation in patients with BM.

Identification of lncRNA and mRNA expression profiles in dorsal root ganglion in rats with cancer-induced bone pain

BACKGROUND

Cancer-induced bone pain (CIBP) is one of the most severe types of chronic pain which the involved mechanisms are largely unknown. LncRNA has been found to play critical roles in chronic pain. However, its function in peripheral nervous system in CIBP remains unknown. Identifying the different lncRNA expression pattern is essential for understanding the genetic mechanisms underlying the pathogenesis of CIBP.

METHODS

The model was induced by injection of Walker 256 cells into the rat tibia canal. Behavior tests and X-ray microtomography (MicroCT) analysis were performed to verify the model's establishment. L2-L5 DRGs were harvested at 14-day post operation and the differential lncRNA and mRNA expression patterns were investigated by microarray analyses. RT-qPCR analysis and RNA interference were performed for expression and function verifications. Bioinformatics analysis was conducted for further function study.

RESULTS

CIBP rats showed hyperalgesia and the MicroCT analysis showed tibia destruction. A total of 73 lncRNAs and 187 mRNAs were dysregulated. The expressions of several lncRNAs and mRNAs were validated by RT-qPCR experiment. Biological analyses showed that the changed mRNAs were mainly related to cellular and single-organism process, cell and cell part, binding function and immune system pathway. The top 30 lncRNA-predicted mRNAs are mainly related to peroxisome, DNA-dependent DNA replication, double-stranded RNA binding, tuberculosis and purine metabolism. 56 lncRNAs (30 downregulated and 26 upregulated) and 179 DEGs (35 downregulated and 144 upregulated) have a significant correlation and constructed a co-expression network. Downregulation of lncRNA NONRATT021203.2 by siRNA intrathecal injection increased PWL and WBD in CIBP rats, alleviating cancer induced bone hyperalgesia.

CONCLUSION

LncRNA played important roles in regulation of CIBP or mRNA expression in peripheral neuropathy in CIBP. These alterd mRNAs and lncRNAs might be potential therapeutic targets for the treatment of CIBP.

Molecular mediators of breast cancer metastasis

Breast cancer has the highest incidence rate of malignancy in women worldwide. A major clinical challenge faced by patients with breast cancer treated by conventional therapies is frequent relapse. This relapse has been attributed to the cancer stem cell (CSC) population that resides within the tumor and possess stemness properties. Breast CSCs are generated when breast cancer cells undergo epithelial-mesenchymal transition resulting in aggressive, highly metastatic, and invasive phenotypes that exhibit resistance towards chemotherapeutics. Metastasis, a phenomenon that aids in the migration of breast CSCs, occurs through any of three different routes: hematogenous, lymphatic, and transcoelomic. Hematogenous dissemination of breast CSCs leads to metastasis towards distant unrelated organs like lungs, liver, bone, and brain causing secondary tumor generation. Activation of metastasis genes or silencing of metastasis suppressor genes often leads to the advancement of metastasis. This review focuses on various genes and molecular factors that have been implicated to regulate organ-specific breast cancer metastasis by defying the available therapeutic interventions.

A rare case report: an inextricable shoulder pain as the exclusive presentation of lung adenocarcinoma with metastasis over contralateral clavicle

Background

Lung cancer is the fourth most common form of the tumor spreading to the bone. Among all patients of lung carcinoma, the most common sites of bone metastasis are vertebrae, ribs, and pelvis. By comparison, the clavicle is an extremely rare site of metastases not only in the population of lung cancers but among all types of tumors. Enlightened by this existing fact, we would like to share our experience of management of an uncommon clavicular metastasis and illuminate the obscure mechanism of its scarcity.

Case presentation

A 56-year-old female without any preknown systemic disease had suffered from a sole intermittent right shoulder pain without any other discomfort for 3 months. Physical examination performed at our orthopedic department showed tenderness over the right distal third of the clavicle with limited range-of-motion of the right shoulder. EGFR-mutated lung adenocarcinoma with metastasis over the right clavicle resulting in a pathological fracture was diagnosed according to the result of the incisional biopsy. Concurrent chemoradiation therapy accompanied with target therapy was performed. Eighteen months postoperatively, the clavicle pain was found to be subsided with stationary bony lesion under appropriate medication and palliative radiotherapy during the subsequent follow-up.

Conclusions

The clavicle is an exceedingly unusual site with 2% of metastatic involvement of all type of tumors and only 1% among the population of carcinoma of lung due to its scanty red marrow and sparse vascular supply. Despite the unpleasant prognosis of clavicular metastasis from primary lung adenocarcinoma, promising quality of life is achievable under multidisciplinary management.

Modulation of Rat Cancer-Induced Bone Pain is Independent of Spinal Microglia Activity

The dissemination of cancer to bone can cause significant cancer-induced bone pain (CIBP), severely impairing the patient's quality of life. Several rodent models have been developed to explore the nociceptive mechanisms of CIBP, including intratibial inoculation of breast carcinoma cells in syngeneic Sprague Dawley rats. Using this model, we investigated whether resident spinal microglial cells are involved in the transmission and modulation of CIBP, a long-debated disease feature. Immunohistochemical staining of ionizing calcium-binding adaptor molecule 1 (Iba-1) and phosphorylated p38-mitogen-activated protein kinase (P-p38 MAPK) showed no spinal microglial reaction in cancer-bearing rats, independently of disease stage, sex, or carcinoma cell line. As a positive control, significant upregulation of both Iba-1 and P-p38 was observed in a rat model of neuropathic pain. Additionally, intrathecal administration of the microglial inhibitor minocycline did not ameliorate pain-like behaviors in cancer-bearing rats, in contrast to spinal morphine administration. Our results indicate that microglial reaction is not a main player in CIBP, adding to the debate that even within the same models of CIBP, significant variations are seen in disease features considered potential drug targets. We suggest that this heterogeneity may reflect the clinical landscape, underscoring the need for understanding the translational value of CIBP models.

Adipose Tissue from Lean and Obese Mice Induces a Mesenchymal to Epithelial Transition-Like Effect in Triple Negative Breast Cancers Cells Grown in 3-Dimensional Culture

Breast cancer is the second leading cause of cancer-related mortality among women globally with obesity being one risk factor. Obese breast cancer patients have at least a 30% increased risk of death from breast cancer compared to non-obese breast cancer patients because they present with larger tumors and generally have increased rates of metastasis. Moreover, obese breast cancer patients respond more poorly to treatment compared to non-obese patients, particularly pre-menopausal women diagnosed with triple negative breast cancer (TNBC). To help understand the molecular mechanisms underlying the increased metastasis associated with obesity, we previously established a three-dimensional culture system that permits the co-culture of adipocytes and TNBC cells in a manner that mimics an in vivo milieu. Using this system, we demonstrate that white adipose tissue from both lean and obese mice can induce a partial mesenchymal-to-epithelial transition (MET). Triple negative breast cancer cells adopt an epithelial morphology and have an increased expression of some epithelial markers, but they maintain the expression of mesenchymal markers, furnishing the breast cancer cells with hybrid properties that are associated with more aggressive tumors. Thus, these data suggest that adipose tissue has the potential to promote secondary tumor formation in lean and obese women. Further work is needed to determine if targeting the partial MET induced by adipose tissue could reduce metastasis.

Spine and Non-spine Bone Metastases - Current Controversies and Future Direction

Bone is a common site of metastases in advanced cancers. The main symptom is pain, which increases morbidity and reduces quality of life. The treatment of bone metastases needs a multidisciplinary approach, with the main aim of relieving pain and improving quality of life. Apart from systemic anticancer therapy (hormonal therapy, chemotherapy or immunotherapy), there are several therapeutic options available to achieve palliation, including analgesics, surgery, local radiotherapy, bone-seeking radioisotopes and bone-modifying agents. Long-term use of non-steroidal analgesics and opiates is associated with significant side-effects, and tachyphylaxis. Radiotherapy is effective mainly in localised disease sites. Bone-targeting radionuclides are useful in patients with multiple metastatic lesions. Bone-modifying agents are beneficial in reducing skeletal-related events. This overview focuses on the role of surgery, including minimally invasive treatments, conventional radiotherapy in spinal and non-spinal bone metastases, bone-targeting radionuclides and bone-modifying agents in achieving palliation. We present the clinical data and their associated toxicity. Recent advances are also discussed.

MDA-9/Syntenin (SDCBP): Novel gene and therapeutic target for cancer metastasis

The primary cause of cancer-related death from solid tumors is metastasis. While unraveling the mechanisms of this complicated process continues, our ability to effectively target and treat it to decrease patient morbidity and mortality remains disappointing. Early detection of metastatic lesions and approaches to treat metastases (both pharmacological and genetic) are of prime importance to obstruct this process clinically. Metastasis is complex involving both genetic and epigenetic changes in the constantly evolving tumor cell. Moreover, many discrete steps have been identified in metastatic spread, including invasion, intravasation, angiogenesis, attachment at a distant site (secondary seeding), extravasation and micrometastasis and tumor dormancy development. Here, we provide an overview of the metastatic process and highlight a unique pro-metastatic gene, melanoma differentiation associated gene-9/Syntenin (MDA-9/Syntenin) also called syndecan binding protein (SDCBP), which is a major contributor to the majority of independent metastatic events. MDA-9 expression is elevated in a wide range of carcinomas and other cancers, including melanoma, glioblastoma multiforme and neuroblastoma, suggesting that it may provide an appropriate target to intervene in metastasis. Pre-clinical studies confirm that inhibiting MDA-9 either genetically or pharmacologically profoundly suppresses metastasis. An additional benefit to blocking MDA-9 in metastatic cells is sensitization of these cells to a second therapeutic agent, which converts anti-invasion effects to tumor cytocidal effects. Continued mechanistic and therapeutic insights hold promise to advance development of truly effective therapies for metastasis in the future.

Tumour innervation and neurosignalling in prostate cancer

Prostate cancer progression has been shown to be dependent on the development of autonomic nerves into the tumour microenvironment. Sympathetic nerves activate adrenergic neurosignalling that is necessary in early stages of tumour progression and for initiating an angiogenic switch, whereas parasympathetic nerves activate cholinergic neurosignalling resulting in tumour dissemination and metastasis. The innervation of prostate cancer seems to be initiated by neurotrophic growth factors, such as the precursor to nerve growth factor secreted by tumour cells, and the contribution of brain-derived neural progenitor cells has also been reported. Current experimental, epidemiological and clinical evidence shows the stimulatory effect of tumour innervation and neurosignalling in prostate cancer. Using nerves and neurosignalling could have value in the management of prostate cancer by predicting aggressive disease, treating localized disease through denervation and relieving cancer-associated pain in bone metastases.

What's that big thing on your head? Diagnosis of a large frontoparietal lesion on an Eastern Zhou skull from Henan, China

We carried out a differential diagnosis of a large frontoparietal lesion on a human skull from a Late Bronze Age archaeological site located on the Central Plain of China, dating to between 771 and 476 BC. The head of this individual was covered in cinnabar, a mercury-based pigment that later was used for medicinal purposes in China. The lesion was well-circumscribed and involved the outer and inner tables of the skull, slight diploë thickening, and coarsening of bone trabeculae with expansion of intertrabecular spaces. We show that the observed changes are most consistent with cavernous hemangioma of the skull, a benign vascular malformation that preferentially affects older adults. Hemangiomas are often neglected in the paleopathological literature because of their benign nature - they tend to be asymptomatic and do not affect quality of life to a significant degree. Nevertheless, they produce characteristic lesions that can be confused with several other conditions with unrelated etiologies, including congenital hemoglabinopathies, traumas, malignant or benign neoplasms, and Paget's disease. We outline the diagnostic criteria that distinguish cavernous hemangioma from other conditions affecting the skull.

Quantitative imaging of platinum-based antitumor complexes in bone tissue samples using LA-ICP-MS

There is a need for effective medication against bone metastases because todays drugs are not able to penetrate the bone and reach the affected areas. To analyze if current or future platinum-containing drugs are able to achieve this, a quantitative imaging method is urgently needed. In this study, the platinum distribution in thin sections of mice tibia was determined using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in a spatially resolved manner. The hard bone tissue visible in microscopic images and signals found for calcium and phosphorous recorded via LA-ICP-MS and micro X-ray fluorescence spectroscopy (μXRF) correlate well. Furthermore, the platinum concentration was quantified using polymer-based matrix-matched standards. A limit of detection of 6 μg/g and a linearity of almost three decades could be achieved. Concentrations surpassing 300 μg/g could be found in the tibia samples. The method presented herein is a powerful approach for the visualization and quantification of platinum. As such, this method is a valuable tool to unravel the mechanism of delivery and optimize the therapeutic potency of platinum-containing drugs targeting bone diseases like bone metastases.

Principles of Management of Extremity Skeletal Metastasis

Understanding the epidemiology of extremity skeletal metastasis and the factors deciding the treatment decision-making are essential in developing a diagnostic and treatment strategy. This leads to optimum care and reduces disease-related burden. With the evolution of medical, radiation therapy, and surgical methods, cancer care has improved the quality of life for patients with improved survival and functional status in patients with skeletal metastasis. Based on the currently available literature, we have described a step-wise evaluation and management strategy of metastatic extremity bone disease. The present review article addresses various aspects and related controversies related to evaluation, staging, and treatment options in the management of extremity bone metastasis. This article also highlights the role of multidisciplinary involvement in management of extremity skeletal metastasis.

Indirect Evaluation of Bone Saturation with Zoledronic Acid After Long-Term Dosing

BACKGROUND

Zoledronic acid (ZA), a potent bisphosphonate used for treatment of bone metastasis, has high bone affinity. This post hoc analysis evaluated the effects of long-term treatment and reduction in dosing frequency of ZA on bone saturation.

MATERIALS AND METHODS

Pharmacokinetic data from three independent studies, OPTIMIZE-2 (patients receiving ≥9 doses of bisphosphonates) and two phase I studies, CZOL4460503 and CZOL4460506 (patients who were bisphosphonate naïve/bisphosphonate free for ≥1 year after previous dosing), were pooled. Serial urine and plasma samples were used as surrogate markers to determine ZA plasma area under the curve (AUC) over 6 hours (AUC_0-6h) and dose excreted in urine over 6 hours (urine_0-6h). Potential relationships between the number of years for which patients had been treated previously at time of study entry and AUC_0-6h or urine_0-6h were analyzed graphically.

RESULTS

Creatinine clearances for patients were similar across the three studies and at all time points analyzed. The levels of AUC_0-6h ZA in plasma at week 0 in every (q) 4 and q12 weekly arms of OPTIMIZE-2 were 0.366 h × mg/L and 0.397 h × mg/L compared with 0.345 h × mg/L and 0.356 h × mg/L in CZOL4460503 and CZOL4460506, respectively. In OPTIMIZE-2, the AUC_0-6h ZA plasma levels were the same (0.428 h × mg/L) at week 36 in both q4 and q12 arms. The levels of ZA urine_0-6h at week 36 in OPTIMIZE-2 (q4 and q12 week arms), CZOL4460503, and CZOL4460506 were 36.6%, 30.8%, 26.5%, and 27.3%, respectively.

CONCLUSION

Long-term ZA treatment may not impact bone saturation, and ZA dosing frequency does not seem to influence drug retention rates.

IMPLICATIONS FOR PRACTICE

Zoledronic acid (ZA), used along with standard antineoplastic therapy to treat bone metastases associated with solid tumors and multiple myeloma, requires frequent (every 3-4 or every 12 weeks) long-term administration. This may result in bone saturation and subsequently lead to a higher risk of adverse events such as osteonecrosis of the jaw and atypical fractures. This post hoc analysis used surrogate markers to demonstrate that prolonged ZA administration does not cause bone saturation. Furthermore, reduction in ZA dosing frequency does not affect its retention level in bones over time. These findings will help in addressing clinicians' concerns regarding prolonged ZA administration.

Novel bisphosphonates with antiresorptive effect in bone mineralization and osteoclastogenesis

Bisphosphonates such as zoledronic, alendronic and risedronic acids are a class of drugs clinically used to prevent bone density loss and osteoporosis. Novel P-C-P bisphosphonates were synthesized for targeting human farnesyl pyrophosphate synthase (hFPPS) and human geranylgeranyl pyrophosphate synthase (hGGPPS), key enzymes of the mevalonate pathway, and capable of anti-proliferative action on a number of cell lines (PC3, MG63, MC3T3, RAW 264.7, J774A.1, bone marrow cells and their co-colture with PC3) involved in bone homeostasis, bone formation and death. Among sixteen compounds, [1-hydroxy-2-(pyrimidin-2-ylamino)ethane-1,1-diyl]bis(phosphonic acid) (10) was effective in reducing PC3 and RAW 264.7 cell number in crystal-violet and cell-dehydrogenase activity assays at 100 μM concentration. 10 reduced differentiated osteoclasts number similarly with zoledronic acid in osteoclastogenesis assay. At nanomolar concentrations, 10 was more effective than zoledronic acid in inducing mineralization in MC3T3 and murine bone marrow cells. Further, 10 significantly inhibited the activity of hFPPS showing an IC₅₀ of 0.31 μM and a remarkable hydroxyapatite binding of 90%. Docking calculations were performed identifying putative interactions between some representative novel bisphosphonates and both hFPPS and hGGPPS. Then, 10 was found to behave similarly or even better than zoledronic acid as a anti-resorptive agent.

Understanding the Progression of Bone Metastases to Identify Novel Therapeutic Targets

Bone is one of the most preferential target site for cancer metastases, particularly for prostate, breast, kidney, lung and thyroid primary tumours. Indeed, numerous chemical signals and growth factors produced by the bone microenvironment constitute factors promoting cancer cell invasion and aggression. After reviewing the different theories proposed to provide mechanism for metastatic progression, we report on the gene expression profile of bone-seeking cancer cells. We also discuss the cross-talk between the bone microenvironment and invading cells, which impacts on the tumour actions on surrounding bone tissue. Lastly, we detail therapies for bone metastases. Due to poor prognosis for patients, the strategies mainly aim at reducing the impact of skeletal-related events on patients' quality of life. However, recent advances have led to a better understanding of molecular mechanisms underlying bone metastases progression, and therefore of novel therapeutic targets.

A mathematical model for describing the metastasis of cancer in bone tissue

Metastasis is the rapid proliferation of cancer cells (secondary tumour) at a specific place, generally leading to death. This occurs at anatomical parts providing the necessary environment for vascularity, oxygen and food to hide their actions and trigger the rapid growth of cancer. Prostate and breast cancers, for example, use bone marrow for their proliferation. Bone-supporting cancer cells thus adapt to the environment, mimicking the behaviour of genetic and molecular bone cells. Evidence of this has been given in Cecchini et al. (2005, EAU Update Ser. 3:214-226), providing arguments such as how cancer cell growth is so active during bone reabsorption. This paper simulates metastasis activation in bone marrow. A mathematical model has been developed involving the activation of molecules from bone tissue cells, which are necessary for cancer to proliferate. Here, we simulate two forms of secondary tumour growth depending on the type of metastasis: osteosclerosis and osteolysis.

Epithelial plasticity, cancer stem cells and bone metastasis formation

Acquisition of an invasive phenotype of cancer cells in primary tumors is an absolute requirement for bone metastasis. The majority of bone metastases is derived from epithelial cancers, particularly those of the breast and prostate. Accumulating evidence suggest that transformed epithelial cells can activate embryonic programs of epithelial plasticity and switch from a sessile, epithelial phenotype to a motile, mesenchymal phenotype also referred to as epithelial-to-mesenchymal transition (EMT). Induction of EMT can, therefore, lead to invasion of surrounding stroma, intravasation, dissemination and colonization of distant sites. In bone/bone marrow disseminated tumor cells can partially regain their original epithelial characteristics via a mesenchymal-to-epithelial transition (MET) as glandular structures in bone metastasis are frequently observed. To date, the importance of epithelial plasticity in cancer cells disseminated to the bone/bone marrow microenvironment has remained largely elusive. Interestingly, a number of growth factors that play a prominent role in EMT induction in the primary tumor have been identified as important stimulators of skeletal metastasis formation. Recent studies have demonstrated that EMT may render cancer cells with properties of stem cells, which in turn can lead to escape from immune surveillance, increased resistance to apoptosis, diminished senescence and, last-but-not least, therapy resistance. This review will discuss current concepts regarding the role of epithelial plasticity in the multistep processes of bone metastasis, the issue of minimal residual disease, cancer stem cells and the importance of EMT in the development of novel targeted drug therapy.

Osteotropic cancers: from primary tumor to bone

It has long been recognized that primary cancers spread to distant organs with characteristic preference. Bone metastases occur in approximately 70% of patients with advanced breast and prostate cancer, causing severe morbidity and hospitalization. In the last decade, we have gained a better understanding of the mechanisms by which certain tumor types tend to metastasize specifically to bone. It appears that the interaction between the organ microenvironment and cancer cells is fundamental for establishing metastatic growth. Accordingly, Stephen Paget's 'seed and soil' hypothesis - stating that circulating cancer cells (the 'seeds') disperse in all directions, but can accomplish metastases only in organs where the microenvironment (the 'soil') is permissive for their growth - still holds forth today. For this reason, this review uses the 'seed and soil' hypothesis as a template to discuss novel insight and developments in the bone metastasis field.

TGF-beta and BMP7 interactions in tumour progression and bone metastasis

The skeleton is the second most frequent site of metastasis. However, only a restricted number of solid cancers, especially those of the breast and prostate, are responsible for the majority of the bone metastases. Metastatic bone disease is a major cause of morbidity, characterised by severe pain and high incidence of skeletal and haematopoietic complications (fractures, spinal cord compression and bone marrow aplasia) requiring hospitalisation. Despite the frequency of skeletal metastases, the molecular mechanisms for their propensity to colonise bone are poorly understood and treatment options are often unsatisfactory. TGF-beta and the signalling pathway it controls appears to play major roles in the pathogenesis of many carcinomas, both in their early stages, when TGF-beta acts to arrest growth of many cell types, and later in cancer progression when it contributes, paradoxically, to the phenotype of tumour invasiveness. Here we discuss some novel insights of the TGF-beta superfamily-including BMPs and their antagonists-in the formation of bone metastasis. Increasing evidence suggests that the TGF-beta superfamily is involved in bone homing, tumour dormancy, and development of micrometastases into overt bone metastases. The established role of TGF-beta/BMPs and their antagonists in epithelial plasticity during embryonic development closely resembles neoplastic processes at the primary site as well as in (bone) metastasis. For instance, the tumour-stroma interactions occurring in the tissue of cancer origin, including epithelium-to-mesenchyme transition (EMT), bear similarities with the role of bone matrix-derived TGF-beta in skeletal metastasis formation.

Predictive value of osteocalcin and β-CrossLaps in metastatic breast cancer

OBJECTIVES

Assessment of the diagnostic value of serum CEA, CA 15.3, osteocalcin (OC) and beta-CrossLaps (beta-CTX) in the detection of metastatic breast cancer.

DESIGN AND METHODS

This study included 47 patients with breast cancer (20 non-metastatic breast cancer, 11 bone metastasis, 11 soft tissue metastasis, 5 bone plus soft tissue metastasis), 10 patients with benign breast lesions and 13 healthy volunteers. CEA and CA 15.3 were determined using microparticle enzyme immunoassay; while OC and beta-CTX were measured by electrochemiluminescence immunoassay.

RESULTS

CEA, CA 15.3, OC and beta-CTX median levels were higher in breast cancer patients compared to controls (p=0.006, 0.001, 0.004 and 0.038, respectively). Increased levels of OC and beta-CTX were demonstrated in bone metastatic patients compared to non-metastatic or soft tissue metastatic patients (p=0.000).

CONCLUSIONS

Combined use of OC and beta-CTX could be useful in early detection of bone metastatic breast cancer which might improve the outcome of the disease.

Skeletal complications and the use of bisphosphonates in metastatic prostate cancer

Metastatic prostate cancer represents an incurable progression of the disease that accounts for the vast majority of disease related mortality and is associated with significant skeletal morbidity with events including bone pain, fractures and spinal cord compression. This article provides an overview of the bone disease in this patient group, with a specific focus on the role of bisphosphonate use, in addressing quality of life issues. Key clinical trial data relating to bisphosphonates is presented and discussed, culminating in key management guidelines.