New and emerging therapies for bone metastases in genitourinary cancers

Comprehensive review of solid tumor bone marrow metastasis

Bone marrow metastasis (BMM) of solid tumors refers to a group of diseases that originate from non-hematopoietic malignant tumor cells invading the bone marrow (BM) through complex metastatic patterns. If BMM identification is delayed, the disease will rapidly develop into disseminated carcinogenesis of the BM, which manifests as a series of hematological disorders and microangiopathic hemolytic anemia, leading to serious life-threatening conditions. Although the study of solid tumor BMM is receiving increasing attention, study remains limited, and most descriptions are derived from case reports. Currently, clinicians have insufficient understanding of BMM, and BMM occurrence is often not recognized early or treated effectively, resulting in high mortality rates. In this article, we review the epidemiology, molecular mechanisms, clinical diagnosis, treatment, and prognosis of solid tumor BMM.

Bone scan with technetium 99m-methyl diphosphonate, the missing link in the initial staging of muscle-invasive bladder carcinoma

BACKGROUND

Accurate staging is crucial to determine the type of treatment for patients with bladder cancer (BCa), especially in high-risk cases. We aimed to assess the role of bone scan in the initial staging of muscle-invasive bladder carcinoma (MIBC).

MATERIAL AND METHODS

Forty-five patients with MIBC were referred to our tertiary clinic to perform a technetium 99m-methyl diphosphonate (Tc99m-MDP) bone scan from January 2019 to March 2020. The patients underwent bone scintigraphy with pelvic SPECT/CT before radical cystectomy. Whole-body scanning was performed 4 hours after Tc99m-MDP injection in both anterior and posterior views. Since the most common bone involvement site in these patients is the pelvic bones and the spine, pelvic SPECT/CT was performed in all patients.

RESULTS

Frequency of skeletal metastasis was 26.7%. Only 19% of the metastases were detected by previous pelvic CT/MRI images performed for routine staging. All the reported skeletal metastases by previous anatomical imaging methods were detected in the bone scan. There was no statistically significant correlation between bone metastasis and the patient's age, lymph nodes metastasis (LNM), hydronephrosis, and muscle-invasive type. The mean serum calcium level was 8.7 ± 0.57 in patients with bone metastasis and 8.87 ± 0.99 in patients without bone metastasis, which was not statistically significant.

CONCLUSION

Bone scan has higher diagnostic performance than conventional imaging methods for detecting bone metastases. It changed the management plan in 8.8% of our patients, so we conclude that performing a whole-body bone scan in the initial staging of MIBC would be helpful.

Transarterial Chemoembolization for the Palliation of Painful Bone Metastases Refractory to First-Line Radiotherapy

PURPOSE

To compare the efficacy and safety of transarterial chemoembolization for the palliation of radiotherapy (RT)-failure bone metastases (BMs) with those of re-radiotherapy (Re-RT) in achieving pain relief.

MATERIALS AND METHODS

Fifty consecutive patients with RT-failure BMs who had undergone Re-RT (23 patients) and transarterial chemoembolization (27 patients) were retrospectively analyzed. The primary endpoint was clinical response, and the secondary endpoints were objective response and adverse events. Pain assessment was performed using the numerical rating scale, and tumor response was evaluated using the modified Response Evaluation Criteria in Solid Tumors. Pain relief was defined as lack of pain with no analgesic usage (complete pain response) or a decrease in pain score by ≥3 points with analgesic usage (partial pain response).

RESULTS

The pain relief rates in the Re-RT and transarterial chemoembolization groups were 57% and 92%, respectively (P = .006). The median pain relief duration was 2 and 3 months in the Re-RT and transarterial chemoembolization groups, respectively (P = .002). The 6-month pain-free survival rates were 30% and 51% in the Re-RT and transarterial chemoembolization groups, respectively (P = .08). The median tumor reduction rates were -4% and 9% in the Re-RT and transarterial chemoembolization groups, respectively (P < .001). The objective response rates were 0% and 11% in the Re-RT and transarterial chemoembolization groups, respectively (P = .29). No serious adverse events or complications were observed.

CONCLUSIONS

Transarterial chemoembolization achieved a superior response rate and longer duration of palliation in symptomatic RT-failure BMs.

Clinical implication of prognostic and predictive biomarkers for castration-resistant prostate cancer: a systematic review

Background

Diagnosis of metastatic castrate resistant prostate cancer (mCRPC) with current biomarkers is difficult and often results in unnecessary invasive procedures as well as over-diagnosis and over-treatment. There are a number of prognostic biomarkers for CRPC, but there are no validated predictive biomarkers to guide in clinical decision-making. Specific biomarkers are needed that enable to understand the natural history and complex biology of this heterogeneous malignancy, identify early response to treatment outcomes and to identify the population of men most likely to benefit from the treatment. In this systematic review, we discuss the existing literature for the role of biomarkers in CRPC and how they aid in the prognosis, treatment selection and survival outcomes.

Methods

We performed a literature search on PubMed and EMBASE databases from January 2015 through February 2020 in accordance to Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Articles were assessed to identify relevant observational studies and randomized controlled trials regarding biomarkers which aid in identifying progression to mCRPC as well as predictive biomarkers which help in treatment selection.

Results

We identified 3640 number of hits of which 58 articles were found to be relevant. Here we addressed biomarkers in the context of prognosis, prediction and patient selection of therapy. These biomarkers were found to be effective as prognostic or predictive factors under variety of conditions. The higher levels for all these biomarkers were associated with shorter median OS and sometimes PFS. Lower amounts of biomarkers in serum or urine were associated with prolonged survival outcomes, longer time to CRPC development or CRPC progression and longer median follow-up irrespective of any therapy.

Conclusion

We observed that the biomarkers included in our study predicted clinically relevant survival outcomes and treatment exposure. Though the current biomarkers are prognostic when measured prior to initiating treatment, not all are validated as predictive markers in post treatment setting. A greater understanding of biomarkers in CRPC is need of the hour for development of more personalized approach to maximize benefit and minimize harm in men with CRPC.

Management of bone complications in patients with genitourinary malignancies

Skeletal metastases are common in genitourinary malignancies-including prostate cancer, renal cell carcinoma, and urothelial cancer-and portend significant morbidity and poor prognosis. The presence of skeletal metastases can result in decreased quality of life and increased morbidity. Strategies can be employed to prevent bone-related complications including lifestyle modifications and dietary supplementation. Additionally, pharmacologic agents exist to prevent bone loss and may be appropriate for patients at high risk of fragility-related or skeletal complications, such as pathologic fracture related to bone metastases. Finally, advancement in effective systemic treatments, particularly novel hormone-targeted agents and immunotherapies, may limit the morbidity of advanced disease and delay the onset of skeletal-related complications.

Regulatory signaling network in the tumor microenvironment of prostate cancer bone and visceral organ metastases and the development of novel therapeutics

This article describes cell signaling network of metastatic prostate cancer (PCa) to bone and visceral organs in the context of tumor microenvironment and for the development of novel therapeutics. The article focuses on our recent progress in the understanding of: 1) The plasticity and dynamics of tumor–stroma interaction; 2) The significance of epigenetic reprogramming in conferring cancer growth, invasion and metastasis; 3) New insights on altered junctional communication affecting PCa bone and brain metastases; 4) Novel strategies to overcome therapeutic resistance to hormonal antagonists and chemotherapy; 5) Genetic-based therapy to co-target tumor and bone stroma; 6) PCa-bone-immune cell interaction and TBX2-WNTprotein signaling in bone metastasis; 7) The roles of monoamine oxidase and reactive oxygen species in PCa growth and bone metastasis; and 8) Characterization of imprinting cluster of microRNA, in tumor–stroma interaction. This article provides new approaches and insights of PCa metastases with emphasis on basic science and potential for clinical translation. This article referenced the details of the various approaches and discoveries described herein in peer-reviewed publications. We dedicate this article in our fond memory of Dr. Donald S. Coffey who taught us the spirit of sharing and the importance of focusing basic science discoveries toward translational medicine.

Serum calcium, alkaline phosphotase and hemoglobin as risk factors for bone metastases in bladder cancer

Early detection of bone metastases is helpful for the treatment of bladder cancer (BC). In this study, we investigated the potential risk factors for bone metastasis in newly diagnosed patients with BC. A total of 902 patients diagnosed with BC between January 2000 and August 2016 were retrospectively reviewed. Of these patient, 50 (5.5%) were identified with bone metastasis. The serum levels of alkaline phosphatase (ALP) and calcium were significantly higher in patients with bone metastases than those without bone metastases (P = 0.015 and P<0.001). And the concentration of hemoglobin (HB) was significant lower in bone metastatic patients compared with non bone metastatic patients (P = 0.009). Multivariate logistic regression analysis indicated that ALP, HB and calcium were independent risk factors for bone metastases in patients with BC. The cut off values of ALP, HB and calcium were 116 U/L, 37.5g/L and 2.54 mmol/L according to the receiver operating characteristic (ROC) curves analysis. And combined ALP, HB with calcium had the highest diagnostic accuracy for predicting bone metastases in BC patients (AUC = 0.760, P<0.001). Therefore, for newly diagnosed patients with BC, the concentrations of ALP >116 U/L, HB <37.5 g/Land calcium >2.54 mmol/L were the risk factors for developing bone metastases. Combined ALP, HB with calcium was more useful to diagnose the bone metastases.

Pilot study on the detection of antiandrogen resistance using serial diffusion-weighted imaging of bone metastases in prostate cancer

PURPOSE

To evaluate serial apparent diffusion coefficient (ADC) measurements of bone metastases in prostate cancer to determine whether antiandrogen resistance can be detected and time to progression estimated.

MATERIALS AND METHODS

Diffusion-weighted imaging (DWI) was performed at 1.5T in nine patients with treatment-naïve metastatic prostate cancer (20 lesions) before antiandrogen treatment, after 1, 2, and 3 months of treatment, and thereafter every 4 months over 31 months or until antiandrogen resistance was detected. Tumor volumes were stable over time. Time courses of the ADCs when averaged over entire lesions and on functional diffusion maps (fDMs) were analyzed using marginal linear model (MLM) analysis.

RESULTS

Starting at 1 month, MLM analysis revealed decreasing mean ADCs (P = 0.001) over time. Simultaneously, the percentage of voxels with significantly higher ADCs decreased (P = 0.004), whereas the percentage of voxels with significantly lower ADCs increased (P < 0.001) on fDMs. Both mean ADCs (P = 0.042) and percentages of voxels with significantly higher ADCs on fDMs (P = 0.039) decreased more rapidly over time in patients with a shorter progression-free interval (PFI). Likewise, higher (P = 0.001) and more rapidly increasing (P = 0.002) percentages of voxels with significantly lower ADCs on fDMs were associated with a shorter PFI.

CONCLUSION

The results of our pilot study suggest that the evolution of ADCs over time may permit early identification of antiandrogen resistance in bone metastases. J. Magn. Reson. Imaging 2016;43:1407-1416.

Trial Design and Objectives for Castration-Resistant Prostate Cancer: Updated Recommendations From the Prostate Cancer Clinical Trials Working Group 3

PURPOSE

Evolving treatments, disease phenotypes, and biology, together with a changing drug development environment, have created the need to revise castration-resistant prostate cancer (CRPC) clinical trial recommendations to succeed those from prior Prostate Cancer Clinical Trials Working Groups.

METHODS

An international expert committee of prostate cancer clinical investigators (the Prostate Cancer Clinical Trials Working Group 3 [PCWG3]) was reconvened and expanded and met in 2012-2015 to formulate updated criteria on the basis of emerging trial data and validation studies of the Prostate Cancer Clinical Trials Working Group 2 recommendations.

RESULTS

PCWG3 recommends that baseline patient assessment include tumor histology, detailed records of prior systemic treatments and responses, and a detailed reporting of disease subtypes based on an anatomic pattern of metastatic spread. New recommendations for trial outcome measures include the time to event end point of symptomatic skeletal events, as well as time to first metastasis and time to progression for trials in the nonmetastatic CRPC state. PCWG3 introduces the concept of no longer clinically benefiting to underscore the distinction between first evidence of progression and the clinical need to terminate or change treatment, and the importance of documenting progression in existing lesions as distinct from the development of new lesions. Serial biologic profiling using tumor samples from biopsies, blood-based diagnostics, and/or imaging is also recommended to gain insight into mechanisms of resistance and to identify predictive biomarkers of sensitivity for use in prospective trials.

CONCLUSION

PCWG3 moves drug development closer to unmet needs in clinical practice by focusing on disease manifestations most likely to affect prognosis adversely for therapeutics tested in both nonmetastatic and metastatic CRPC populations. Consultation with regulatory authorities is recommended if a trial is intended to seek support for drug approval.

Effect of denosumab versus zoledronic acid in preventing skeletal-related events in patients with bone metastases by baseline characteristics

BACKGROUND

Analyses of phase III trials showed that denosumab was superior to zoledronic acid (ZA) in preventing skeletal-related events (SREs) irrespective of age, history of SREs, or baseline pain status. This analysis assessed the risk of SREs across additional baseline characteristics.

PATIENTS AND METHODS

Patients (N = 5543) from three phase III trials who had breast cancer, prostate cancer, or other solid tumours and one or more bone metastasis were included. Superiority of denosumab versus ZA in reducing risk of first SRE and first and subsequent SREs was assessed in subgroups defined by the Eastern Cooperative Oncology Group performance status (ECOG PS), bone metastasis location, bone metastasis number, visceral metastasis presence/absence, and urinary N-telopeptide (uNTx) level using Cox proportional hazards and Anderson-Gill models. Subgroups except bone metastasis location were also assessed for each solid tumour type.

RESULTS

Compared with ZA, denosumab significantly reduced the risk of first SRE across all subgroups (hazard ratio [HR] ranges: ECOG PS, 0.79-0.84; bone metastasis location, 0.78-0.83; bone metastasis number, 0.78-0.84; visceral metastasis presence/absence, 0.80-0.82; uNTx level, 0.73-0.86) and reduced the risk of first and subsequent SREs in all subgroups (HR ranges: ECOG PS, 0.76-0.83; bone metastasis location, 0.78-0.84; bone metastasis number, 0.79-0.81; visceral metastasis presence/absence, 0.79-0.81; uNTx level, 0.74-0.83). Similar results were observed in subgroups across tumour types.

CONCLUSION

Denosumab was superior to ZA in preventing SREs in patients with bone metastases from advanced cancer, regardless of ECOG PS, bone metastasis number, baseline visceral metastasis presence/absence, and uNTx level.

Does the onset of bone metastasis in sunitinib-treated renal cell carcinoma patients impact the overall survival?

PURPOSE

To evaluate the impact of bone metastasis (BM) onset toward prognosis in metastatic renal cell carcinoma (mRCC) patients treated with sunitinib.

METHODS

mRCC patients with BM and sunitinib as first targeted therapy between May 2005 and December 2012 were retrospectively analyzed. Patients with synchronous (s) BM or metachronous (m) BM were compared with regard to treatment and outcome [time to clinical progression (TTcP), overall survival (OS), skeletal-related events (SRE)]. Descriptive statistics, Kaplan-Meier estimation of TTcP and OS, Cox regression analyses, and a landmark analysis were administered.

RESULTS

BM was identified in 127 mRCC patients; thereof, 82 sunitinib-treated patients were analyzed [sBM n = 57 (69.5 %), mBM n = 25 (30.5 %)]. Higher tumor grading (p = 0.029), male predominance (p = 0.02), and less second-line therapy (p = 0.001) were detected in sBM compared to mBM. SRE remained similar between subgroups (p = 0.462). TTcP during sunitinib was similar [median sBM 8.1 (95 % CI 3.9-12.3) vs. mBM 8.7 (95 % CI 2.7-14.8) months, p = 0.903]. OS remained significantly inferior in sBM patients compared to mBM [median sBM 21.1 (95 % CI 16-26.2) months vs. mBM 38.5 (95 % CI 15-62) months, p = 0.001], which was confirmed by landmark analyses at 1.5, 3, 6, 9, and 12 months. However, OS after occurrence of BM was similar in both groups [median sBM 24.2 (95 % CI 17.3-31.1) months vs. mBM 17.2 (95 % CI 8.4-26) months, p = 0.519].

CONCLUSIONS

mBM is associated with an improved OS compared to sBM in mRCC with sunitinib treatment, despite similar efficacy of sunitinib treatment in both groups of patients.

Clinical efficacy of denosumab versus bisphosphonates for the prevention of bone complications: implications for nursing

Antiresorptive therapies are used for the prevention of skeletal-related events (SREs) associated with metastatic bone disease related to breast cancer, prostate cancer, and other solid tumors. This review highlights the central role of nurses in supporting and educating advanced cancer patients regarding the consequences of bone metastases and SREs, including therapy management options. Contemporary clinical journals reporting evidence-based studies were reviewed. SREs associated with bone metastases can significantly impact the quality of life of advanced cancer patients. Denosumab therapy, an advancement in antiresorptive treatments, significantly prevents and delays the time to develop SREs. In the multifaceted approach required for successful and consistent management of SREs associated with bone metastases, antiresorptive therapies can play a central role in maintaining the functional independence of patients through the prevention of debilitating SREs, thereby preserving quality of life.

Valproic acid (VPA) inhibits the epithelial-mesenchymal transition in prostate carcinoma via the dual suppression of SMAD4

PURPOSES

The epithelial-mesenchymal transition (EMT) plays an important role in cancer metastasis. Previous studies have reported that valproic acid (VPA) suppresses prostate carcinoma (PCa) cell metastasis and down-regulates SMAD4 protein levels, which is the key molecule in TGF-β-induced EMT. However, the correlation between VPA and the EMT in PCa remains uncertain.

METHODS

Markers of the EMT in PCa cells and xenografts were molecularly assessed after VPA treatment. The expression and mono-ubiquitination of SMAD4 were also analyzed. After transfection with plasmids that express SMAD4 or short hairpin RNA for SMAD4 down-regulation, markers of EMT were examined to confirm whether VPA inhibits the EMT of PCa cells through the suppression of SMAD4.

RESULTS

VPA induced the increase in E-cadherin (p < 0.05), and the decrease in N-cadherin (p < 0.05) and Vimentin (p < 0.05), in PCa cells and xenografts. SMAD4 mRNA and protein levels were repressed by VPA (p < 0.05), whereas the level of mono-ubiquitinated SMAD4 was increased (p < 0.05). SMAD4 knockdown significantly increased E-cadherin expression in PC3 cells, but SMAD4 over-expression abolished the VPA-mediated EMT-inhibitory effect.

CONCLUSIONS

VPA inhibits the EMT in PCa cells via the inhibition of SMAD4 expression and the mono-ubiquitination of SMAD4. VPA could serve as a promising agent in PCa treatment, with new strategies based on its diverse effects on posttranscriptional regulation.

Loss of Androgen-Regulated MicroRNA 1 Activates SRC and Promotes Prostate Cancer Bone Metastasis

Bone metastasis is the hallmark of progressive and castration-resistant prostate cancers. MicroRNA 1 (miR-1) levels are decreased in clinical samples of primary prostate cancer and further reduced in metastases. SRC has been implicated as a critical factor in bone metastasis, and here we show that SRC is a direct target of miR-1. In prostate cancer patient samples, miR-1 levels are inversely correlated with SRC expression and a SRC-dependent gene signature. Ectopic miR-1 expression inhibited extracellular signal-regulated kinase (ERK) signaling and bone metastasis in a xenograft model. In contrast, SRC overexpression was sufficient to reconstitute bone metastasis and ERK signaling in cells expressing high levels of miR-1. Androgen receptor (AR) activity, defined by an AR output signature, is low in a portion of castration-resistant prostate cancer. We show that AR binds to the miR-1-2 regulatory region and regulates miR-1 transcription. Patients with low miR-1 levels displayed correlated low canonical AR gene signatures. Our data support the existence of an AR-miR-1-SRC regulatory network. We propose that loss of miR-1 is one mechanistic link between low canonical AR output and SRC-promoted metastatic phenotypes.

Denosumab for the prevention of skeletal complications in metastatic castration-resistant prostate cancer: comparison of skeletal-related events and symptomatic skeletal events

In this analysis of a phase III trial in patients with castration-resistant prostate cancer and bone metastases, treatment with denosumab reduced the risk of skeletal complications vs zoledronic acid regardless of whether the end point was defined as SSE or SRE. Both SSEs and SREs were associated with development of moderate/severe pain among patients with no/mild pain at baseline.

Background

In a phase III trial in patients with castration-resistant prostate cancer (CRPC) and bone metastases, denosumab was superior to zoledronic acid in reducing skeletal-related events (SREs; radiation to bone, pathologic fracture, surgery to bone, or spinal cord compression). This study reassessed the efficacy of denosumab using symptomatic skeletal events (SSEs) as a prespecified exploratory end point.

Patients and methods

Patients with CRPC, no previous bisphosphonate exposure, and radiographic evidence of bone metastasis were randomized to subcutaneous denosumab 120 mg plus i.v. placebo every 4 weeks (Q4W), or i.v. zoledronic acid 4 mg plus subcutaneous placebo Q4W during the blinded treatment phase. SSEs were defined as radiation to bone, symptomatic pathologic fracture, surgery to bone, or symptomatic spinal cord compression. The relationship between SSE or SRE and time to moderate/severe pain was assessed using the Brief Pain Inventory Short Form.

Results

Treatment with denosumab significantly reduced the risk of developing first SSE [HR, 0.78; 95% confidence interval (CI) 0.66–0.93; P = 0.005] and first and subsequent SSEs (rate ratio, 0.78; 95% CI 0.65–0.92; P = 0.004) compared with zoledronic acid. The treatment differences in the number of patients with SSEs or SREs were similar (n = 48 and n = 45, respectively). Among patients with no/mild pain at baseline, both SSEs and SREs were associated with moderate/severe pain development (P < 0.0001). Fewer patients had skeletal complications, particularly fractures, when defined as SSE versus SRE.

Conclusion

In patients with CRPC and bone metastases, denosumab reduced the risk of skeletal complications versus zoledronic acid regardless of whether the end point was defined as SSE or SRE.

Bone-targeted therapies for elderly patients with renal cell carcinoma: current and future directions

Bone metastases are very common in advanced renal cell carcinoma (RCC) and can have a huge impact on quality of life by leading to skeletal-related events (SREs), including pain, pathologic fractures and spinal cord compression with need for surgery or radiotherapy. Because of their osteolytic aspect and biologic behaviour, these SREs are more common in patients with bone metastases from RCC than from other malignancies. As overall survival is increased by new anti-angiogenic drugs like tyrosine kinase inhibitors and mammalian target of rapamycin inhibitors, the incidence of SREs is rising, making the clinical management of bone metastases in RCC ever more important, especially in the more vulnerable elderly patient. In this review we discuss the current advances and future directions in bone-targeted therapies in patients with RCC with a special focus on the elderly population. Recently, two bone-targeted agents have been approved in the prevention of SREs in advanced RCC: zoledronic acid and denosumab. To date, there is no specific data on the use of bisphosphonates or denosumab in the elderly and specific studies in this setting are warranted. We compare the available evidence for the use and implications of both agents in the elderly patient and give general information on safety concerns that could be more important in these patients.

Targeting integrin α6 stimulates curative-type bone metastasis lesions in a xenograft model

Laminin-binding integrin receptors are key mediators of epithelial cell migration and tumor metastasis. Recent studies have demonstrated a role for the α6 integrin (ITGA6/CD49f) in maintaining stem cell compartments within normal bone marrow and in residency of tumors metastatic to bone. In this study, we tested a function-blocking antibody specific for ITGA6, called J8H, to determine if preexisting cancer lesions in bone could be slowed and/or animal survival improved. Human prostate tumors were established by intracardiac injection into male SCID mice and treatment with J8H antibody was initiated after 1 week. Tumor progression was monitored by micro-computed tomography (CT) imaging of skeletal lesions. Animals that received weekly injections of the anti-ITGA6 antibody showed radiographic progression in only 40% of osseous tumors (femur or tibia), compared with control animals, where 80% of the lesions (femur or tibia) showed progression at 5 weeks. Kaplan-Meier survival analysis demonstrated a significant survival advantage for J8H-treated animals. Unexpectedly, CT image analysis revealed an increased proportion of bone lesions displaying a sclerotic rim of new bone formation, encapsulating the arrested lytic lesions in animals that received the anti-ITGA6 antibody treatment. Histopathology of the sclerotic lesions demonstrated well-circumscribed tumor within bone, surrounded by fibrosis. These data suggest that systemic targeting of the ITGA6-dependent function of established tumors in bone may offer a noncytotoxic approach to arrest the osteolytic progression of metastatic prostate cancer, thereby providing a new therapeutic strategy for advanced disease.

Development of a realistic in vivo bone metastasis model of human renal cell carcinoma

About one-third of patients with advanced renal cell carcinoma (RCC) have bone metastases. The incidence of RCC is increasing and bone metastatic RCC merits greater focus. Realistic preclinical bone metastasis models of RCC are lacking, hampering the development of effective therapies. We developed a realistic in vivo bone metastasis model of human RCC by implanting precision-cut tissue slices under the renal capsule of immunodeficient mice. The presence of disseminated cells in bone marrow of tissue slice graft (TSG)-bearing mice was screened by human-specific polymerase chain reaction and confirmed by immunohistology using human-specific antibody. Disseminated tumor cells in bone marrow of TSG-bearing mice derived from three of seven RCC patients were detected as early as 1 month after tissue implantation at a high frequency with close resemblance to parent tumors (e.g., CAIX expression and high vascularity). The metastatic patterns of TSGs correlated with disease progression in patients. In addition, TSGs retained capacity to metastasize to bone at high frequency after serial passaging and cryopreservation. Moreover, bone metastases in mice responded to Temsirolimus treatment. Intratibial injections of single cells generated from TSGs showed 100 % engraftment and produced X-ray-visible tumors as early as 3 weeks after cancer cell inoculation. Micro-computed tomography (μCT) and histological analysis revealed osteolytic characteristics of these lesions. Our results demonstrated that orthotopic RCC TSGs have potential to develop bone metastases that respond to standard therapy. This first reported primary RCC bone metastasis model provides a realistic setting to test therapeutics to prevent or treat bone metastases in RCC.

Distribution of metastatic sites in patients with prostate cancer: A population-based analysis

BACKGROUND

There is few data on what constitutes the distribution of metastatic sites in prostate cancer (PCa). The aim of our study was to systematically describe the most common sites of metastases in a contemporary cohort of PCa patients.

METHODS

Patients with metastatic PCa were abstracted from the Nationwide Inpatient Sample (1998-2010). Most common metastatic sites within the entire population were described. Stratification was performed according to the presence of single or multiple (≥ 2 sites) metastases. Additionally, we evaluated the distribution of metastatic sites amongst patients with and without bone metastases.

RESULTS

Overall, 74,826 patients with metastatic PCa were identified. The most common metastatic sites were bone (84%), distant lymph nodes (10.6%), liver (10.2%), and thorax (9.1%). Overall, 18.4% of patients had multiple metastatic sites involved. When stratifying patients according to the site of metastases, only 19.4% of men with bone metastases had multiple sites involved. Conversely, among patients with lymph nodes, liver, thorax, brain, digestive system, retroperitoneum, and kidney and adrenal gland metastases the proportion of men with multiple sites involved was 43.4%, 76.0%, 76.7%, 73.0%, 52.2%, 60.9%, and 76.4%, respectively. When focusing exclusively on patients with bone metastases, the most common sites of secondary metastases were liver (39.1%), thorax (35.2%), distant lymph nodes (24.6%), and brain (12.4%).

CONCLUSIONS

Although the majority of patients with metastatic PCa experience bone location, the proportion of patients with atypical metastases is not negligible. These findings might be helpful when planning diagnostic imaging procedures in patients with advanced PCa.

Radium-223 chloride: Extending life in prostate cancer patients by treating bone metastases

The treatment scope for patients with metastatic castrate-resistant prostate cancer (mCRPC) is rapidly expanding. On May 15, 2013, the U.S. Food and Drug Administration (FDA) approved radium-223 chloride ((223)RaCl2) for the treatment of mCRPC patients whose metastases are limited to the bones. Radium-223 is an α-emitting alkaline earth metal ion, which, similar to calcium ions, accumulates in the bone. In a phase III study (ALSYMPCA), mCRPC patients with bone metastases received best standard-of-care treatment with placebo or (223)RaCl2. At a prespecified interim analysis, the primary endpoint of median overall survival was significantly extended by 3.6 months in patients treated with radium-223 compared with placebo (P < 0.001). The radioisotope was well tolerated and gave limited bone marrow suppression. (223)RaCl2 is the first bone-targeting antitumor therapy that received FDA approval based on a significant extended median overall survival. Further studies are required to optimize its dosing and to confirm its efficacy and safety in cancer patients.

Pathobiology and management of prostate cancer-induced bone pain: recent insights and future treatments

Prostate cancer (PCa) has a high propensity for metastasis to bone. Despite the availability of multiple treatment options for relief of PCa-induced bone pain (PCIBP), satisfactory relief of intractable pain in patients with advanced bony metastases is challenging for the clinicians because currently available analgesic drugs are often limited by poor efficacy and/or dose-limiting side effects. Rodent models developed in the past decade show that the pathobiology of PCIBP comprises elements of inflammatory, neuropathic and ischemic pain arising from ectopic sprouting and sensitization of sensory nerve fibres within PCa-invaded bones. In addition, at the cellular level, PCIBP is underpinned by dynamic cross talk between metastatic PCa cells, cellular components of the bone matrix, factors associated with the bone microenvironment as well as peripheral components of the somatosensory system. These insights are aligned with the clinical management of PCIBP involving use of a multimodal treatment approach comprising analgesic agents (opioids, NSAIDs), radiotherapy, radioisotopes, cancer chemotherapy agents and bisphosphonates. However, a major drawback of most rodent models of PCIBP is their short-term applicability due to ethical concerns. Thus, it has been difficult to gain insight into the mal(adaptive) neuroplastic changes occurring at multiple levels of the somatosensory system that likely contribute to intractable pain at the advanced stages of metastatic disease. Specifically, the functional responsiveness of noxious circuitry as well as the neurochemical signature of a broad array of pro-hyperalgesic mediators in the dorsal root ganglia and spinal cord of rodent models of PCIBP is relatively poorly characterized. Hence, recent work from our laboratory to develop a protocol for an optimized rat model of PCIBP will enable these knowledge gaps to be addressed as well as identification of novel targets for drug discovery programs aimed at producing new analgesics for the improved relief of intractable PCIBP.

Novel therapies for the treatment of advanced prostate cancer

In recent years, great success has been achieved on many fronts in the treatment of men with metastatic castration-resistant prostate cancer (CRPC), including novel chemotherapeutics, immunotherapies, bone microenvironment-targeted agents, and hormonal therapies. Numerous agents are currently in early-phase clinical trial development for the treatment of advanced prostate cancer. These novel therapies target several areas of prostate tumor biology, including the upregulation of androgen signaling and biosynthesis, critical oncogenic intracellular pathways, epigenetic alterations, and cancer immunology. Importantly, the characterization of the prostate cancer genome offers the potential to exploit conserved genetic alterations, which may increase the efficacy of these targeted therapies. Predictive and prognostic biomarkers are urgently needed to maximize therapeutic efficacy and safety of these promising new treatments options in prostate cancer.