Bone metastases in breast cancer: higher prevalence of osteosclerotic lesions

Research progress of bone metastases: From disease recognition to clinical practice

Bone metastases, as one of the common types of metastatic tumors, have a great impact on the survival period and quality of life of patients. Bone metastases are usually characterized by bone destruction. Skeletal related events caused by bone destruction often lead to pain, pathological fractures and even paralysis. In this review, we provide a detailed explanation of bone metastases from the epidemiology, clinical features, pathogenesis, and recently developed clinical treatment viewpoints. We concluded that the incidence of bone metastases is increasing gradually, with serious clinical symptoms, complex pathogenesis and diverse clinical treatment. Tumor cells, immune cells, osteoblasts/osteoclasts and other cells as well as cytokines and enzymes all play a key role in the pathogenesis of bone metastases. We believe that the future treatment of bone metastases will be diversified and comprehensive. Some advanced technologies, such as nanomedicine, could be used for treatment, but this depends on understanding how disease occurs. With the development of treatment, the survival time and quality of life of patients will be improved.

Cross Talk Between Macrophages and Cancer Cells in the Bone Metastatic Environment

The skeleton is a common site for cancer metastases with the bone microenvironment providing the appropriate conditions for cancer cell colonization. Once in bone, cancer cells effectively manipulate their microenvironment to support their growth and survival. Despite previous efforts to improve treatment modalities, skeletal metastases remain with poor prognoses. This warrants an improved understanding of the mechanisms leading to bone metastasis that will aid development of effective treatments. Macrophages in the tumor microenvironment are termed tumor associated macrophages (TAMs) and their crosstalk with cancer cells is critical in regulating tumorigenicity in multiple cancers. In bone metastases, this crosstalk is also being increasingly implicated but the specific signaling pathways remain incompletely understood. Here, we summarize the reported functions, interactions, and signaling of macrophages with cancer cells during the metastatic cascade to bone. Specifically, we review and discuss how these specific interactions impact macrophages and their profiles to promote tumor development. We also discuss the potential of targeting this crosstalk to inhibit disease progression. Finally, we identify the remaining knowledge gaps that will need to be addressed in order to fully consider therapeutic targeting to improve clinical outcomes in cancer patients.

Temperature Monitoring in Hyperthermia Treatments of Bone Tumors: State-of-the-Art and Future Challenges

Bone metastases and osteoid osteoma (OO) have a high incidence in patients facing primary lesions in many organs. Radiotherapy has long been the standard choice for these patients, performed as stand-alone or in conjunction with surgery. However, the needs of these patients have never been fully met, especially in the ones with low life expectancy, where treatments devoted to pain reduction are pivotal. New techniques as hyperthermia treatments (HTs) are emerging to reduce the associated pain of bone metastases and OO. Temperature monitoring during HTs may significantly improve the clinical outcomes since the amount of thermal injury depends on the tissue temperature and the exposure time. This is particularly relevant in bone tumors due to the adjacent vulnerable structures (e.g., spinal cord and nerve roots). In this Review, we focus on the potential of temperature monitoring on HT of bone cancer. Preclinical and clinical studies have been proposed and are underway to investigate the use of different thermometric techniques in this scenario. We review these studies, the principle of work of the thermometric techniques used in HTs, their strengths, weaknesses, and pitfalls, as well as the strategies and the potential of improving the HTs outcomes.

Assessment of Bone Lesions with 18F-FDG PET Compared with 99mTc Bone Scintigraphy Leads to Clinically Relevant Differences in Metastatic Breast Cancer Management

It is unknown whether assessment of potential bone lesions in metastatic breast cancer (MBC) by ¹⁸F-FDG PET instead of ^99mTc bone scintigraphy (BS) supports clinically relevant changes in MBC management. Therefore, we retrospectively compared management recommendations based on bone lesion assessment by ¹⁸F-FDG PET plus contrast-enhanced CT (ceCT) or BS plus ceCT, for patients with newly diagnosed MBC. Methods: Baseline ceCT, BS, and ¹⁸F-FDG PET for all patients included in the IMPACT-MBC study (NCT01957332) at the University Medical Center Groningen were reviewed for bone lesions. If bone lesions were found by any imaging modality, virtual MBC management recommendations were made by a multidisciplinary expert panel, based on either ¹⁸F-FDG PET plus ceCT or BS plus ceCT. The panel had access to standard clinicopathologic information and baseline imaging findings outside the skeleton. Clinically relevant management differences between the 2 recommendations were defined either as different treatment intent (curative, noncurative, or unable to determine) or as different systemic or local treatment. If no bone lesions were found by any imaging modality, the patients were included in the analyses without expert review. Results: In total, 3,473 unequivocal bone lesions were identified in 102 evaluated patients (39% by ceCT, 26% by BS, and 87% by ¹⁸F-FDG PET). Additional bone lesions on ¹⁸F-FDG PET plus ceCT compared with BS plus ceCT led to change in MBC management recommendations in 16% of patients (95% CI, 10%-24%). BS also changed management compared with ¹⁸F-FDG PET in 1 patient (1%; 95% CI, 0%-5%). In 26% (95% CI, 19%-36%) of patients, an additional ¹⁸F-FDG PET exam was requested, because BS provided insufficient information. Conclusion: In this exploratory analysis of newly diagnosed MBC patients, ¹⁸F-FDG PET versus BS to assess bone lesions resulted in clinically relevant management differences in 16% of patients. BS delivered insufficient information in over one fourth of patients, resulting in an additional request for ¹⁸F-FDG PET. On the basis of these data, ¹⁸F-FDG PET should be considered a primary imaging modality for assessment of bone lesions in newly diagnosed MBC.

Bone metastases: a comprehensive review of the literature

The last report of the World Health Organization (WHO) stated that approximately four million people experience bone pain due to malignant diseases. Among them, metastatic bone pain is one of the most important sources of complaint. The estimated median survival in the presence of bone metastases ranks from 10 to 12 weeks. Bone represents a potential target of distant metastases for the majority of malignant tumours. However, the exact incidence of bone metastases is unknown. Bone metastases have an important socio-economic impact, and due to the enhancement of the overall survivorship, their incidence is increasing. Malignant neoplasms such as lung, thyroid, renal cancer, multiple myeloma, and melanoma often metastasize to the bone. Bone metastases commonly localize to the spinal column, pelvis, shoulder, and distal femur. The proper treatment for painful skeletal metastases is still unknown. Hence, the purpose of this review of the literature was to update current evidence concerning the aetiogenesis, biological behaviour, and treatment algorithms for painful skeletal metastases.

Early response of bone metastases can predict tumor response in patients with non-small-cell lung cancer with bone metastases in the treatment with nivolumab

The effect of nivolumab and the relation between bone response and tumor control in patients with non-small-cell lung cancer (NSCLC) with bone metastases are not clear. The outcome of nivolumab monotherapy was investigated, and whether the response of bone metastases is useful as an early predictor of tumor control in patients with NSCLC with bone metastases was examined. The participants included 15 patients who received nivolumab monotherapy for NSCLC with bone metastases in our institution between 2015 and 2017. Tumor control was defined using Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST1.1). Response of bone metastases was assessed by the MD Anderson response criteria (MDA criteria). Responses according to RECIST1.1 and the MDA criteria were classified as responder (complete response or partial response) and non-responder [progressive disease (PD) or stable disease]. Progression-free survival (PFS) was investigated using the Kaplan-Meier method. With RECIST1.1, the overall response rate was 20%. Multivariate analysis showed that the MDA criteria were the only risk factor for patients with PD (RECIST1.1). Median PFS was 1.9 months, with PFS of 20% at 6 months. Univariate analysis showed that being a non-responder according to the MDA criteria was the only risk factor for PFS. In patients who were responders (MDA criteria) within 3 months, PFS was 83 and 50% at 3 and 6 months, respectively, though all non-responder (MDA criteria) patients converted to PD (RECIST1.1) within 3 months. Response according to RECIST1.1 was significantly correlated with response according to the MDA criteria (P<0.05). In patients who were both responders according to RECIST1.1 and the MDA criteria, time to response with the MDA criteria (1.4-2.0 months) was earlier than with RECIST1.1 (2.8-3.0 months) in all patients. In conclusion, application of the MDA criteria within 2 months of nivolumab monotherapy is useful for early prediction of response and prognosis in patients with NSCLC with bone metastases.

Female sex is associated with a lower risk of bone metastases and favourable prognosis in non-sex-specific cancers

Background

The objectives were to investigate the disparity in the prevalence of bone metastases (BM) between the sexes and to assess the effect of female sex on the development and prognosis of BM.

Methods

Cases of invasive non-sex-specific cancers diagnosed between 2010 and 2015 in the Surveillance, Epidemiology, and End Results (SEER) program were used. The prevalence of BM was calculated by combining the prevalence of BM among different cancers. Multivariable logistic regression and proportion hazard regression were conducted to investigate the effect of female sex, and the results were pooled by meta-analysis.

Results

The pooled prevalence of BM among male and female patients was 2.3% (95% CI: 1.6–3.2%) and 1.8% (95% CI: 1.2–2.6%), respectively. The pooled prevalence of BM dramatically decreased for patients aged 11–40 years old, plateaued for patients aged 41–90 years old and increased for patients aged > 90 years old in both male and female patients. Meta-analysis suggested that female sex had a protective effect on the development of BM (pooled OR = 0.80; 95% CI: 0.75–0.84; p < .001) and a favourable prognosis for respiratory system cancers (pooled HR = 0.81; 95% CI: 0.71–0.92; p < .001). However, no significant associations existed for other cancers. Male non-sex-specific cancer patients and those with male-leaning genetic variations or hormonal status have a greater likelihood of developing BM than female patients.

Conclusions

Female sex was associated with fewer BM in various non-sex-specific cancers, and the effect was constant with changes in age. Female sex showed a protective effect exclusively on the prognosis of respiratory system cancers.

Extensive Re-ossification and Reformation of the Proximal Femur After External Beam Radiotherapy in Metastatic Carcinoma Breast

Management of metastatic bone disease is still evolving and is dependent upon many factors including the primary tumour type, expected life expectancy, site and size of lesion, character of the lesion, lytic or blastic, and the number of lesions. Active orthopaedic surgical intervention is usually required at the time of pathological fracture either impending or actual. Management options are either in situ fixation or replacement/arthroplasty. The role of post-operative radiotherapy is still not clearly defined and its biological effect on healing of pathological fracture is unclear. In this report, we describe a case of breast carcinoma with a large metastatic lytic lesion in the proximal femur, which was treated by in situ fixation followed by hormonal therapy and external beam radiotherapy. In the post-operative period, rapid and dramatic ossification and reformation of the proximal femur was observed.

Effect of Bone Reading CT software on radiologist performance in detecting bone metastases from breast cancer

OBJECTIVE

To evaluate the effect of CT software that generates rib unfolding images and automatically numbers ribs and thoracic spines on radiologist performance in detecting thoracic bone metastases from breast cancer.

METHODS

A total of 126 patients with breast cancer who underwent chest CT and fludeoxyglucose (FDG)-positron emission tomography (PET)/CT and/or bone scans were retrospectively reviewed. One board-certified radiologist (R1) and one radiology resident (R2) independently assessed the original chest CT and rib unfolding images using a commercially available post-processing software (Bone Reading) application to evaluate metastasis in the ribs and thoracic spines. Results were compared with reference standard based on CT, FDG-PET/CT and/or bone scan with follow-up.

RESULTS

Based on reference standard, 78 metastatic bone lesions in 26 patients were identified. On per-patient-based analysis, Bone Reading assessed by R1/R2 had a sensitivity of 84.6%/80.8% and a specificity of 94.0%/94.0% with an accuracy of 92.1%/91.3%. The original CT reading yielded a sensitivity of 73.1%/57.7% and a specificity of 95.0%/94.0% with an accuracy of 90.5%/86.5%. The sensitivity and accuracy of Bone Reading were significantly higher than those of CT reading, as assessed by R2 (both p = 0.031). On per-lesion-based analysis, Bone Reading assessed by R1/R2 yielded a sensitivity of 84.6%/82.1% and a specificity of 99.7%/99.6% with an accuracy of 99.4%/99.3%, while the original CT reading yielded a sensitivity of 71.8%/62.8% and a specificity of 99.6%/99.5% with an accuracy of 99.2%/98.9%. The sensitivity and accuracy with Bone Reading application were significantly higher than those with CT reading by both readers (R1, p = 0.006 and p = 0.036, respectively; R2, both p < 0.001). The mean reading time needed for Bone Reading application was significantly shorter than that for original chest CT reading (p < 0.001). Bone Reading application helped readers find small and sclerotic lesions missed in original CT reading.

CONCLUSION

In patients with breast cancer, the use of Bone Reading application improved radiologist performance in bone metastasis detection compared with original chest CT reading with reduced reading time. This software will be more helpful to inexperienced radiologists for improving the reading performance. Advances in knowledge: Small and sclerotic lesions can be easily missed in original CT reading. Using Bone Reading CT software can enhance the performance of radiologists in detecting bone metastasis in breast cancer. False-negative rates can be significantly reduced in both inexperienced and experienced readers.

The Breast Cancer to Bone (B2B) Metastases Research Program: a multi-disciplinary investigation of bone metastases from breast cancer

Background

Bone is the most common site of breast cancer distant metastasis, affecting 50–70 % of patients who develop metastatic disease. Despite decades of informative research, the effective prevention, prediction and treatment of these lesions remains elusive. The Breast Cancer to Bone (B2B) Metastases Research Program consists of a prospective cohort of incident breast cancer patients and four sub-projects that are investigating priority areas in breast cancer bone metastases. These include the impact of lifestyle factors and inflammation on risk of bone metastases, the gene expression features of the primary tumour, the potential role for metabolomics in early detection of bone metastatic disease and the signalling pathways that drive the metastatic lesions in the bone.

Methods/Design

The B2B Research Program is enrolling a prospective cohort of 600 newly diagnosed, incident, stage I-IIIc breast cancer survivors in Alberta, Canada over a five year period. At baseline, pre-treatment/surgery blood samples are collected and detailed epidemiologic data is collected by in-person interview and self-administered questionnaires. Additional self-administered questionnaires and blood samples are completed at specified follow-up intervals (24, 48 and 72 months). Vital status is obtained prior to each follow-up through record linkages with the Alberta Cancer Registry. Recurrences are identified through medical chart abstractions. Each of the four projects applies specific methods and analyses to assess the impact of serum vitamin D and cytokine concentrations, tumour transcript and protein expression, serum metabolomic profiles and in vitro cell signalling on breast cancer bone metastases.

Discussion

The B2B Research Program will address key issues in breast cancer bone metastases including the association between lifestyle factors (particularly a comprehensive assessment of vitamin D status) inflammation and bone metastases, the significance or primary tumour gene expression in tissue tropism, the potential of metabolomic profiles for risk assessment and early detection and the signalling pathways controlling the metastatic tumour microenvironment. There is substantial synergy between the four projects and it is hoped that this integrated program of research will advance our understanding of key aspects of bone metastases from breast cancer to improve the prevention, prediction, detection, and treatment of these lesions.

VALIDATION OF THERAPEUTIC RESPONSE ASSESSMENT BY BONE SCINTIGRAPHY IN PATIENTS WITH BONE-ONLY METASTATIC BREAST CANCERS DURING ZOLEDRONIC ACID TREATMENT: COMPARISON WITH COMPUTED TOMOGRAPHY ASSESSMENT

PURPOSE

To validate the use of bone scintigraphy (BS) versus computed tomography (CT) for therapeutic monitoring in patients during treatment with zoledronic acid.

MATERIALS AND METHODS

Eleven patients with bone-only metastatic disease and being treated with zoledronic acid were included. The effects of therapies including chemotherapy and hormone therapy were evaluated in 25 separate examinations in total as follows: complete response (CR), when no bone metastasis was visible; partial response (PR), when a decrease in the lesion area was detected; stable disease (SD), when no or slight change was observed; and progressive disease (PD), when new or enlarged lesion areas were observed.

RESULTS

The accuracies of examination by Readers 1, 2, and 3 respectively were 76%, 80% and 76% for BS, 52%, 48%, and 40% for CT, and 64%, 52% and 60% for BS and CT combined with Readers 2 and 3 observing significant differences between CT and BS results. The rates of interobserver agreement between Readers 1 and 2, between Readers 1 and 3, and between Reader 2 and 3 respectively, were 84%, 80% and 88% (κ = 0.648, 0.561 and 0.766) for BS, 52%, 56%, and 60% (κ = 0.180, 0.278 and 0.282) for CT, and 52%, 60%, and 56% (κ = 0.215, 0.282 and 0.232) for CT and BS combined.

CONCLUSION

BS is effective for assessing the response of bone metastasis to therapy in patients during zoledronic acid treatment.

Differential effect of zoledronic acid on normal trabecular and cortical bone density in oncologic patients with bone metastases

PURPOSE

To evaluate bone density changes at the level of normal bone and bone metastases after zoledronic acid (ZA) treatment in oncologic patients.

MATERIALS AND METHODS

We retrospectively evaluated 72 consecutive adult patients with histologically confirmed solid tumors with at least 1 newly diagnosed bone metastatic lesion. Bone metastases were diagnosed by bone scans and confirmed with computed tomography (CT). Patients received intravenous ZA, 4 mg, by 15-min infusion every 28 day through a peripheral or a central venous access and were monitored for at least 3 months and a maximum of 24 months. Bone density was determined at the level of bone metastases and at the level of normal trabecular and cortical bone using a ROI-based approach.

RESULTS

A significant increase was demonstrated at the level of normal trabecular bone of the calvarium and the femoral neck. No significant increase of density was observed at the level of the normal cortical bone. Bone metastases showed a significant increase in CT density as compared to baseline up to 24 months after zoledronic acid.

CONCLUSION

We have found that long term treatment with ZA increases trabecular bone density in oncologic patients whereas normal cortical bone changes are not detectable.

RANK, RANKL and OPG Expression in Breast Cancer - Influence on Osseous Metastasis

In women, malignant breast tumours are among the most common malignant diseases in Europe. In advanced breast cancer, the risk of bone metastasis increases to 65-75 %. The discovery of the physiological bone metabolism parameters RANK (receptor activator of nuclear factor-κB), RANKL (receptor activator of nuclear factor-κB ligand) and OPG (osteoprotegerin) as well as their pathophysiological involvement in bone-related diseases is the subject of new therapeutic strategies. The formation of osteolytic bone metastasis requires increased osteoclast activity. Activation of osteoclasts by excessive direct RANKL or reduced OPG expression of osseous metastatic tumour cells remains to be elucidated. More than 50 % of primary breast cancer cells express OPG and RANK, while RANKL could be detected only in 14-60 %. Increased OPG concentrations in the serum of patients with bone metastases have been shown in several studies, whereas the RANKL results are described in an opposite manner. The use of OPG as a biomarker for the detection of osteolytic bone metastases is not consistent and needs to be proved in further studies. Increased RANKL activity was found in diseases characterised by excessive bone loss and formed the basis of new therapeutic options. In several studies, a human monoclonal antibody to RANKL (denosumab) was investigated for the treatment of bone diseases. Denosumab is a promising therapeutic option due to its bone-protective effects.

Radionuclide Therapy of Bone Metastases

The skeleton is a potential metastatic target of many malignant tumors. Up to 85% of prostate and breast cancer patients may develop bone metastases causing severe pain syndromes in many of them. In patients suffering from multilocular, mainly osteoblastic lesions and pain syndrome, radionuclide therapy is recommended for pain palliation. Low-energy beta-emitting radionuclides ((153)samarium-ethylenediaminetetrameth-ylenephosphonate (EDTMP) and (89)strontium) deliver high radiation doses to bone metastases and micrometastases in the bone marrow, but only negligible doses to the hematopoietic marrow. The response rate regarding pain syndrome is about 75%; about 25% of the patients may even become pain free. The therapy is repeatable, depending on cell counts. Concomitant treatment with modern bisphosphonates does not interfere with the treatment effects. Clinical trials using a new, not yet approved nuclide ((223)Radium) and/or combinations of chemotherapy and radionuclides are aiming at a more curative approach.

Emerging therapeutic targets in breast cancer bone metastasis

In the past decade, our understanding of the molecular mechanisms that underlie breast cancer pathology and progression has dramatically improved. Using this knowledge, we have identified additional targets and developed novel therapeutic interventions in breast cancer. Together, these translational research efforts are helping to usher us into an age of personalized cancer therapy. Metastasis to bone is a common and devastating consequence of breast cancer. Bisphosphonates, which represent the current gold standard in bone metastasis therapies, are being improved with newer and more efficacious generations of these compounds being developed. Breast cancer growth in the bone requires activation of various signaling pathways in both cancer cells and stromal cells, including those that are stimulated by TGF-β and RANKL, and mediated through the Src tyrosine kinase. Bone cells and cancer cells alike express promising targets for therapeutic intervention, including Cathepsin K, CXCR4 and GPNMB. In this article we discuss the molecular mechanisms behind these pro-metastatic molecules and review the most recent findings in the clinical development of their associated targeted therapies.

Targeting angiogenesis-dependent calcified neoplasms using combined polymer therapeutics

BACKGROUND

There is an immense clinical need for novel therapeutics for the treatment of angiogenesis-dependent calcified neoplasms such as osteosarcomas and bone metastases. We developed a new therapeutic strategy to target bone metastases and calcified neoplasms using combined polymer-bound angiogenesis inhibitors. Using an advanced "living polymerization" technique, the reversible addition-fragmentation chain transfer (RAFT), we conjugated the aminobisphosphonate alendronate (ALN), and the potent anti-angiogenic agent TNP-470 with N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer through a Glycine-Glycine-Proline-Norleucine linker, cleaved by cathepsin K, a cysteine protease overexpressed at resorption sites in bone tissues. In this approach, dual targeting is achieved. Passive accumulation is possible due to the increase in molecular weight following polymer conjugation of the drugs, thus extravasating from the tumor leaky vessels and not from normal healthy vessels. Active targeting to the calcified tissues is achieved by ALN's affinity to bone mineral.

METHODS AND FINDING

The anti-angiogenic and antitumor potency of HPMA copolymer-ALN-TNP-470 conjugate was evaluated both in vitro and in vivo. We show that free and conjugated ALN-TNP-470 have synergistic anti-angiogenic and antitumor activity by inhibiting proliferation, migration and capillary-like tube formation of endothelial and human osteosarcoma cells in vitro. Evaluation of anti-angiogenic, antitumor activity and body distribution of HPMA copolymer-ALN-TNP-470 conjugate was performed on severe combined immunodeficiency (SCID) male mice inoculated with mCherry-labeled MG-63-Ras human osteosarcoma and by modified Miles permeability assay. Our targeted bi-specific conjugate reduced VEGF-induced vascular hyperpermeability by 92% and remarkably inhibited osteosarcoma growth in mice by 96%.

CONCLUSIONS

This is the first report to describe a new concept of a narrowly-dispersed combined polymer therapeutic designed to target both tumor and endothelial compartments of bone metastases and calcified neoplasms at a single administration. This new approach of co-delivery of two synergistic drugs may have clinical utility as a potential therapy for angiogenesis-dependent cancers such as osteosarcoma and bone metastases.

Radiological changes following second-line zoledronic acid treatment in breast cancer patients with bone metastases

Initiation of bisphosphonate therapy in bisphosphonate-naïve patients is known to be associated with radiological changes such as increased bone density in both osteolytic and osteoblastic metastases. It is not known, however, whether switching from a second-generation bisphosphonate to a more potent agent is associated with similar changes. This study aimed to prospectively explore radiological changes, as assessed by thoracolumbar CT scanning, in patients switching from an early generation bisphosphonate (i.e., oral clodronate or intravenous pamidronate) to intravenous zoledronic acid. Patients with progressive bone metastases despite use of an earlier generation bisphosphonate were switched to zoledronic acid as part of a study to evaluate the palliative benefit of this intervention. Quantitative computed tomography (QCT) scanning of the thoracolumbar spine was carried out at baseline, and repeated 4 months after commencing zoledronic acid. The effect of this change of therapy was explored in terms of bone density, as well as volume of osteolytic and osteoblastic disease. Fifteen patients were assessed. Switching of bisphosphonate therapy was associated with a significant increase in bone density, and an increase in osteoblastic volume. There was an insignificant trend towards reduced osteolytic volume. In conclusion, switching from early generation bisphosphonates to a more potent agent is associated with radiological changes similar to those seen when commencing a bisphosphonate in treatment-naïve patients. This is consistent with the observed palliative benefit. The use of QCT may be of benefit in the monitoring of bone metastases.

Orthopedic surgery implications of breast cancer

Breast cancer is the most common malignancy and the second leading cause of death in women. The metastatic involvement of bone denotes disease progression and decreased survival. Controversy exists regarding the exact pathophysiologic mechanism of metastasis and the different pathways that determine an osteoblastic versus osteoclastic bone compromise. Several breakthrough advances in imaging techniques aid in the detection, staging and follow-up of bone metastases. Although usually responsive to hormonal therapy and pharmacologic interventions, skeletal metastases often require some type of surgical intervention. Orthopedic surgeons should establish an active role in the multidisciplinary treatment of patients with breast cancer.

A prospective analysis of CT density measurements of bone metastases after treatment with zoledronic acid

OBJECTIVE

The objective was to prospectively determine CT density changes in bone metastases, before and after intravenous zoledronic acid for a maximum period of 12 months.

PATIENTS AND METHODS

Twenty-three consecutive patients presented with bone metastases and underwent therapy with zoledronic acid from December 2004. All patients underwent CT of the chest, abdomen, and pelvis. Bone density, measured in Hounsfield units (HU), was determined by segmenting lesions in the same anatomical area of the metastasis sites on the axial images of the sequential series of CT examinations. The effects of zoledronic acid were evaluated by calculating absolute and relative increases in bone density.

RESULTS

The patients presented with multiple metastases in 65% of the cases. When compared with the baseline, all groups demonstrated a significant increase in bone density, which significantly (p < 0.01) correlated with the number of zoledronic acid administrations. There was increased bone density of at least 100% in 57%, and an increase of at least 50% in 87% of the patients. This increase was significant in both lytic and sclerotic metastases after 3 months of therapy. No significant bone density difference was found in normal-appearing bone.

CONCLUSION

Bone density measured by CT increases at metastatic sites after zoledronic acid treatment, regardless of the type of metastasis, in contrast to apparently normal bone.