Bone Pain and Muscle Weakness in Cancer Patients

Classical cannabinoid receptors as target in cancer-induced bone pain: a systematic review, meta-analysis and bioinformatics validation

To test the hypothesis that genetic and pharmacological modulation of the classical cannabinoid type 1 (CB1) and 2 (CB2) receptors attenuate cancer-induced bone pain, we searched Medline, Web of Science and Scopus for relevant skeletal and non-skeletal cancer studies from inception to July 28, 2022. We identified 29 animal and 35 human studies. In mice, a meta-analysis of pooled studies showed that treatment of osteolysis-bearing males with the endocannabinoids AEA and 2-AG (mean difference [MD] - 24.83, 95% confidence interval [95%CI] - 34.89, - 14.76, p < 0.00001) or the synthetic cannabinoid (CB) agonists ACPA, WIN55,212-2, CP55,940 (CB1/2-non-selective) and AM1241 (CB2-selective) (MD - 28.73, 95%CI - 45.43, - 12.02, p = 0.0008) are associated with significant reduction in paw withdrawal frequency. Consistently, the synthetic agonists AM1241 and JWH015 (CB2-selective) increased paw withdrawal threshold (MD 0.89, 95%CI 0.79, 0.99, p < 0.00001), and ACEA (CB1-selective), AM1241 and JWH015 (CB2-selective) reduced spontaneous flinches (MD - 4.85, 95%CI - 6.74, - 2.96, p < 0. 00001) in osteolysis-bearing male mice. In rats, significant increase in paw withdrawal threshold is associated with the administration of ACEA and WIN55,212-2 (CB1/2-non-selective), JWH015 and AM1241 (CB2-selective) in osteolysis-bearing females (MD 8.18, 95%CI 6.14, 10.21, p < 0.00001), and treatment with AM1241 (CB2-selective) increased paw withdrawal thermal latency in males (mean difference [MD]: 3.94, 95%CI 2.13, 5.75, p < 0.0001), confirming the analgesic capabilities of CB1/2 ligands in rodents. In human, treatment of cancer patients with medical cannabis (standardized MD - 0.19, 95%CI - 0.35, - 0.02, p = 0.03) and the plant-derived delta-9-THC (20 mg) (MD 3.29, CI 2.24, 4.33, p < 0.00001) or its synthetic derivative NIB (4 mg) (MD 2.55, 95%CI 1.58, 3.51, p < 0.00001) are associated with reduction in pain intensity. Bioinformatics validation of KEGG, GO and MPO pathway, function and process enrichment analysis of mouse, rat and human data revealed that CB1 and CB2 receptors are enriched in a cocktail of nociceptive and sensory perception, inflammatory, immune-modulatory, and cancer pathways. Thus, we cautiously conclude that pharmacological modulators of CB1/2 receptors show promise in the treatment of cancer-induced bone pain, however further assessment of their effects on bone pain in genetically engineered animal models and cancer patients is warranted.

Physical Activity, Alcohol, and Cigarette Use in Urological Cancer Patients over Time since Diagnosis

Urological cancers represent a substantial global public health concern, exerting far-reaching effects on both individuals and their families. There is an urgent need to comprehensively understand the transformations in patients' lifestyles and behaviors, given their critical role in the treatment process and overall well-being. This study, involving 128 urological cancer patients, aims to investigate changes in physical activity levels, problematic drinking behaviors assessed through the Alcohol Use Disorders Identification Test (AUDIT), and smoking habits assessed using the Fagerström Test for Nicotine Dependence (FTND) over four distinct time intervals over the subsequent three years from the time of diagnosis and among individuals diagnosed more than three years ago. The results reveal a significant decrease in physical activity levels between study intervals (p < 0.0001), declining from 69% to 45% between the first and second post-diagnosis assessments. Furthermore, the highest levels of problematic substance use, indicated by mean scores, were noted in the first year following diagnosis (AUDIT: 4.20, p = 0.01; FTND: 4.83, p = 0.08). Given the significant impact of physical activity on the prospects of recovery, it is imperative to delve more deeply into the factors contributing to this decline and devise targeted interventions for its improvement. In the context of substance use, it is essential to ascertain whether the initially high levels are a result of coping with the cancer diagnosis or represent a turning point at which patients modify their behaviors and cease their addiction. A more thorough understanding of this phenomenon would enhance the effectiveness of precisely focused interventions.

Management of cancer pain due to bone metastasis

Bone metastases frequently occur in patients with cancer. Skeletal-related events (SREs), including pain, impaired mobility, hypercalcemia, pathological fracture, spinal cord and nerve root compression, and bone marrow infiltration, can decrease the quality of life of the patients and increase the risk of morbidity. The mechanism of pain due to bone metastasis is complicated and involves various interactions among tumor cells, bone cells, activated inflammatory cells, and bone-innervating neurons. Cancer pain due to bone metastasis can be crippling and a chronic state that causes sarcopenia. For pain management, it is important to diagnose whether the pain is based on background pain or breakthrough pain due to bone metastasis. In addition, the management goal of cancer pain due to bone metastasis is not only to achieve pain relief but also to prevent pain progression and SREs. Pain mechanisms should be applied to achieve optimal management. This review aims to discuss the mechanisms of cancer pain due to bone metastasis and review the recommended drug therapies.

Glycogen synthase kinase-3β inhibition decreases inflammation and relieves cancer induced bone pain via reducing Drp1-mediated mitochondrial damage

Bone is the preferential site of metastasis for breast cancer. Invasion of cancer cells induces the destruction of bone tissue and damnification of peripheral nerves and consequently induced central sensitization which contributes to severe pain. Herein, cancer induced bone pain (CIBP) rats exhibited destruction of tibia, mechanical allodynia and spinal inflammation. Inflammatory response mainly mediated by astrocyte and microglia in central nervous system. Our immunofluorescence analysis revealed activation of spinal astrocytes and microglia in CIBP rats. Transmission electron microscopy (TEM) observations of mitochondrial outer membrane disruption and cristae damage in spinal mitochondria of CIBP rats. Proteomics analysis identified abnormal expression of proteins related to mitochondrial organization and function. Intrathecally, injection of GSK‐3β activity inhibitor TDZD‐8 significantly attenuated Drp1‐mediated mitochondrial fission and recovered mitochondrial function. Inhibition of GSK‐3β activity also suppressed NLRP3 inflammasome cascade and consequently decreased mechanical pain sensitivity of CIBP rats. For cell research, TDZD‐8 treatment significantly reversed TNF‐α induced mitochondrial membrane potential (MMP) deficiency and high mitochondrial reactive oxygen species level. Taken together, GSK‐3β inhibition by TDZD‐8 decreases spinal inflammation and relieves cancer induced bone pain via reducing Drp1‐mediated mitochondrial damage.

Mechanisms of bone pain: Progress in research from bench to bedside

The field of research on pain originating from various bone diseases is expanding rapidly, with new mechanisms and targets asserting both peripheral and central sites of action. The scope of research is broadening from bone biology to neuroscience, neuroendocrinology, and immunology. In particular, the roles of primary sensory neurons and non-neuronal cells in the peripheral tissues as important targets for bone pain treatment are under extensive investigation in both pre-clinical and clinical settings. An understanding of the peripheral mechanisms underlying pain conditions associated with various bone diseases will aid in the appropriate application and development of optimal strategies for not only managing bone pain symptoms but also improving bone repairing and remodeling, which potentially cures the underlying etiology for long-term functional recovery. In this review, we focus on advances in important preclinical studies of significant bone pain conditions in the past 5 years that indicated new peripheral neuronal and non-neuronal mechanisms, novel targets for potential clinical interventions, and future directions of research.

Interventional and Non-interventional Medical Rehabilitation Approaches to Axial Spine Pain in Vertebral Metastatic Disease

As targeted therapies help patients with advanced cancer live longer, interventions for management of axial spine pain will become more common. Unfortunately, the indications for and safety of these procedures have been relatively unexplored compared with non-cancer adults. This review focuses on the following aspects of axial spine pain management in patients with vertebral metastatic disease: (1) pathophysiology and symptoms of cancer- and non-cancer-related spine pain; (2) safety and efficacy of non-interventional rehabilitation approaches to treat this pain; (3) considerations for interventional pain approaches to acute and chronic pain in patients with vertebral metastatic disease. This review also summarizes gaps in the literature and describes specific cases in which the described interventions have been applied.

Spine Pain and Metastatic Prostate Cancer: Defining the Contribution of Nonmalignant Etiologies

PURPOSE

In patients with metastatic prostate cancer (MPC), the contribution of nonmalignant etiologies to morbidity is often overlooked.

METHODS

We retrospectively reviewed the documented specialist assessments of back pain in men with MPC in a joint medical oncology and physiatry clinic at our tertiary cancer care center. Data on cancer disease extent, hormonal status, sites of spread, pain characteristics, physiatric examination findings, imaging, and recommended management were reviewed, extracted, and codified. For those with back pain at a site of known disease, pain etiology was classified as malignant, nonmalignant, or mixed.

RESULTS

Ninety-three men were collaboratively assessed for back pain, 24 (26%) with a biochemical recurrence and 69 (74%) with MPC of whom 53 (77%) reported pain in an area of known spinal metastases including 35 (66%) metastatic castration-resistant disease and 34 (64%) a precancer history of back pain. The presenting pain symptoms of the 53 patients were activity-related in 22 (42%), radicular in eight (15%), transitional movement-related in seven (13%), biologic in five (9%), and multifactorial in 11 (21%). Overall, pain was deemed malignant in 20 (38%; five castration-sensitive, 15 metastatic castration resistant prostate cancer), nonmalignant in 12 (23%; four castration-sensitive, eight CRPC), and of mixed etiology in 21 (40%; nine castration-sensitive, 12 CRPC).

CONCLUSION

Nonmalignant etiologies contributed significantly to back pain at sites of metastatic spread for 33/53 (62%) patients with MPC assessed by medical oncology and physiatry. We recommend multidisciplinary care for patients with MPC and back pain to address nonmalignant etiologies that contribute to functional compromise.

Protocol for the Pilot Study of Group Video Yogic Breathing App in Breast Cancer Survivors

INTRODUCTION

Breast cancer remains a leading cause of cancer deaths; however, recent improvements in treatment have improved survivorship. As a result of this improvement, more individuals are living with the long-term side effects of cancer treatment. Therefore, methods that incorporate lifestyle and mind-body approaches are becoming increasingly used in the patient treatment pathway.

METHODS

In this study, PranaScience Institute will develop and test a group video mobile application for Yogic Breathing (YB). YB is shown to reduce symptomatic conditions associated with several conditions including breast cancer. For this initial feasibility study, PranaScience will collaborate with the Medical University of South Carolina to implement the study app-based program in breast cancer survivors. This research is aimed to understand if the YB could be delivered via an app, if participants are able to practice it satisfactorily, and if there is any symptom relief by the YB practice. In the control group, participants will be directed to the Attention Control (AC) feature of the app, which guides users to focus on a mindfulness activity not involving YB. Participants will be randomly assigned to the YB or AC study plan (N = 20 per group). Breast cancer survivors who have completed radiation therapy within last 2 months will be recruited for this study and provided access to the app for a 12-weeks program. The study app will record total practice times. Virtual visits by a study yoga instructor during group video sessions will measure participant compliance with proper technique. Feasibility will be examined by evaluating intervention delivery factors and resource needs. Acceptability of using the mobile study app to support symptom management will be evaluated using a satisfaction and system usability scale. Behavioral survey measures will help guide effect sizes and power calculations for the next larger-scale study. Biomarkers in the saliva (tumor suppressors, cytokines), and fingernails (cortisol, differential proteomics) will be measured at baseline and end of study at 12 weeks.

DISCUSSION

All findings from this pilot study will be synthesized to refine the mobile study app in preparation for large-scale evaluation in Phase II involving all-study site participants with cancer. ClinicalTrials.gov Identifier NCT05161260.

"The use of bisphosphonates to treat skeletal complications in solid tumours"

The skeleton is the most common site of secondary disease in breast cancer and prostate cancer, with up to 80% of patients with advanced disease developing bone metastases (BM). The proportion is also substantial in advanced lung cancer (20%-40%). Because of the high prevalence of cancers of the breast, prostate and lung, these cancers account for more than 80% of cases of metastatic bone disease occurring in solid tumours. Metastatic bone disease is associated with greatly increased bone resorption by osteoclasts, leading to moderate to severe pain and other skeletal complications, with major impact on quality of life (QoL). Skeletal Related Events (SREs) have been defined as: pathological long bone or vertebral fractures; spinal cord compression; need for radiation for pain relief or to prevent fracture/spinal cord compression, need for surgery to bone and hypercalcaemia. More recently, Symptomatic Skeletal Events (SSEs) have been defined to monitor QoL. Although there are currently no curative treatments for metastatic bone disease, patients with breast or prostate cancer and BM are now surviving for several years and sometimes longer, and prevention of SREs is the key aim to optimization of QoL. Since their discovery 50 years ago and their introduction more than 30 years ago into the field of metastatic bone disease, a range of oral and intravenous bisphosphonate drugs have made a major contribution to prevention of SREs. Large trials have clearly demonstrated the clinical value of different bisphosphonate-based drugs (including the oral drugs ibandronate and clodronate and intravenous agents such as zoledronate and pamidronate), in treatment of hypercalcaemia of malignancy and the reduction of SREs and SSEs in a range of cancers. Despite the success of denosumab in reducing osteolysis, bisphosphonates also remain mainstay drugs for treatment of metastatic bone disease. Recognizing the 50th Anniversary of the discovery of bisphosphonates, this review focuses on their continuing value in BM treatment and their future potential, for example in providing a bone-targeting vehicle for cytotoxic drugs.

Interventional Therapies for Pain in Cancer Patients: a Narrative Review

PURPOSE OF REVIEW

Pain is a prevalent symptom in the lives of patients with cancer. In light of the ongoing opioid epidemic and increasing awareness of the potential for opioid abuse and addiction, clinicians are progressively turning to interventional therapies. This article reviews the interventional techniques available to mitigate the debilitating effects that untreated or poorly treated pain have in this population.

RECENT FINDINGS

A range of interventional therapies and technical approaches are available for the treatment of cancer-related pain. Many of the techniques described may offer effective analgesia with less systemic toxicity and dependency than first- and second-line oral and parenteral agents. Neuromodulatory techniques including dorsal root ganglion stimulation and peripheral nerve stimulation are increasingly finding roles in the management of oncologic pain. The goal of this pragmatic narrative review is to discuss interventional approaches to cancer-related pain and the potential of such therapies to improve the quality of life of cancer patients.

Virtual Prehabilitation in Surgical Cancer Patients During the Covid-19 Pandemic: A Prospective Feasibility Study (Preprint)

Background

Since the beginning of the COVID-19 pandemic, preoperative care, also termed prehabilitation, has become increasingly relevant due to the decreasing functional and psychosocial health of patients with cancer, which is a result of the pandemic restrictions. Concurrently, access to telehealth has improved; telehealth comprises all remote care delivery facilitated by information technologies (ie, virtually).

Objective

The aim of this protocol is to describe the rationale and methodology for a major trial investigating the feasibility and safety of multimodal virtual prehabilitation services (ie, teleprehabilitation).

Methods

This single-arm feasibility trial aims to recruit 100 patients with cancer to receive teleprehabilitation throughout their preoperative period. The inclusion criteria are as follows: (1) 18 years of age or older, (2) scheduled for elective cancer surgery and referred by a surgeon, (3) medically cleared by the referring physician to engage in physical activity, and (4) have a good comprehension of the English or French language. Feasibility will be assessed by documenting recruitment, adherence, and retention rates, in addition to patients’ motives for not participating in the trial, low participation, or discontinuation. The secondary outcome of safety will be assessed by reporting program-related adverse events.

Results

The Montreal General Hospital Foundation funded the project in August 2020. The protocol was then approved by the Research Ethics Board of the McGill University Health Centre in January 2021 (ID No. 2021-6730). The first patient was recruited in March 2021, and recruitment is expected to end in September 2022. As of March 2022, 36 patients have been recruited, including 24 who have completed their participation. No adverse events have been reported. Data collection is expected to conclude in November 2022. Data analysis will be performed, and the results will be published by the beginning of 2023.

Conclusions

This trial will provide guidance on the use of telehealth in the administration of prehabilitation services. The trial will provide a large amount of information that will respond to gaps in the literature, as there are minimal reports on the use of telehealth rehabilitation and prehabilitation services among elderly populations and in acute contexts, such as the preoperative period.

Trial Registration

ClinicalTrials.gov NCT0479956; https://clinicaltrials.gov/ct2/show/NCT04799561

International Registered Report Identifier (IRRID)

DERR1-10.2196/29936

Força de preensão, capacidade funcional e qualidade de vida de indivíduos com câncer

RESUMO O objetivo deste estudo foi avaliar a força, capacidade funcional e qualidade de vida de indivíduos com câncer em comparação com valores preditos em indivíduos saudáveis, bem como determinar se força e capacidade funcional são capazes de predizer a qualidade de vida dessa população. Foram avaliados 50 indivíduos com câncer, de acordo com força (dinamômetro Crown), capacidade funcional (teste de AVD-Glittre) e qualidade de vida (SF-36). Os resultados foram comparados aos valores de referência preditos em indivíduos saudáveis, pareados por idade e sexo, pelo teste two-sample Kolmogorov-Smirnov. O coeficiente de correlação de Spearman foi utilizado para avaliar as relações entre as variáveis, e a regressão linear múltipla foi utilizada para avaliar se força e capacidade funcional são capazes de predizer a qualidade de vida. Houve diferença significativa (p<0,01) para força, capacidade funcional e qualidade de vida entre indivíduos com câncer e o predito em indivíduos saudáveis. Bem como, uma correlação significativa entre força e capacidade funcional (ρ=-0,58; p<0,01), entre força e qualidade de vida (ρ=0,46; p<0,01), e qualidade de vida e capacidade funcional (ρ=-0,51; p<0,01). A análise de regressão demonstrou que a capacidade funcional é preditora da qualidade de vida, sendo capaz, sozinha, de explicar 20% (R2=0,195) dessa variável. Assim, indivíduos com câncer apresentaram diminuição significativa na força, capacidade funcional e qualidade de vida se comparados ao predito. Além disso, todas essas variáveis estão correlacionadas em indivíduos com câncer, principalmente, a capacidade funcional e a qualidade de vida.

Prognostic impact of sarcopenia in patients with metastatic hormone-sensitive prostate cancer

BACKGROUND

Cancer cachexia is associated with a poor prognosis. This study aimed to investigate the association between sarcopenia and survival in patients with metastatic hormone-sensitive prostate cancer.

METHODS

We retrospectively evaluated 197 patients diagnosed with metastatic hormone-sensitive prostate cancer in our department and its affiliated institution between January 2008 and December 2015. Sarcopenia was diagnosed according to the sex-specific consensus definition. Castration-resistance prostate cancer-free survival, cancer-specific survival and overall survival from the metastatic hormone-sensitive prostate cancer diagnoses were calculated using the Kaplan-Meier method and compared using the log-rank test. Risk factors affecting the survival outcomes were analyzed using the Cox proportional regression analysis.

RESULTS

In total, 163 patients (82.7%) had sarcopenia. Cancer-specific survival and overall survival were significantly shorter in sarcopenic patients than in non-sarcopenic patients (median cancer-specific survival: 77.0 months vs. not reached, P = 0.0099; overall survival: 72.0 months vs. not reached, P = 0.0465), whereas castration-resistance prostate cancer-free survival did not significantly differ between the groups (P = 0.6063). Multivariate analyses showed that sarcopenia was an independent factor for cancer-specific survival (hazard ratio: 2.18, P = 0.0451), together with the Gleason score (hazard ratio: 1.87, P = 0.0272) and LATITUDE risk classification (hazard ratio: 2.73, P = 0.0008). Moreover, the prognostic association of sarcopenia was remarkable in patients aged <73.0 years (cancer-specific survival: 82.0 months vs. not reached, P = 0.0027; overall survival: 72.0 months vs. not reached, P = 0.0078 in sarcopenic vs. non-sarcopenic patients), whereas the association was not significant in patients aged ≥73.0 years (cancer-specific survival: 76.0 and 75.0 months, respectively, P = 0.7879; overall survival: 67.0 and 52.0 months, respectively, P = 0.7263).

CONCLUSION

Sarcopenia was an independent risk factor of cancer-specific survival in patients with metastatic hormone-sensitive prostate cancer, especially in younger patients.

No Difference in the Phenotypic Expression of Frailty among Elderly Patients Recently Diagnosed with Cancer Vs Cancer Free Patients

OBJECTIVES

To examine frailty determinants differences in patients with a recent diagnosis of cancer compared to non-cancer patients among older adult. Revealing those differences will allow us to individualize the exact frailty management in those patients diagnosed with cancer.

DESIGN

This is an observational cross-sectional, monocentric study.

SETTING

Patients were evaluated at the Geriatric Frailty Clinic (GFC), in the Toulouse University Hospital, France, between October 2011 and February 2016.

PARTICIPANTS

1996 patients aged 65 and older were included (1578 patients without cancer and 418 patients with solid and hematological cancer recently diagnosed).

MEASUREMENTS

Frailty was established according to the frailty phenotype. The frailty phenotype measures five components of frailty: weight loss, exhaustion, low physical activity, weakness and slow gait. Frailty phenotype was categorized as robust, pre-frail and frail.

RESULTS

In a multinomial logistic regression, cancer, compared to the non-cancer group, is not associated with an increased likelihood of being classified as pre frail (RRR 0.9, 95% CI [0.5 ; 1.6 ], p 0.9) or frail (RRR 1.2, 95% CI [0.7 ; 2.0], p 0.4) rather than robust. When considering each Fried criterion, a significant higher odd of weight loss was observed in older patients with cancer compared to the non-cancer patients (OR 2.3, 95% CI [1.8; 3.0], p <0.001) but no statistically significant differences was found among the four other Fried criteria. Sensitivity analysis on the frailty index showed that cancer was not associated with a higher FI score compared to non-cancer (β 0.002, 95%CI [-0.009; 0.01], p 0.6).

CONCLUSION

In this real-life study evaluating elderly patients with and without cancer, we didn't confirm our hypothesis, in fact we found that cancer was not associated with frailty severity using both a phenotypic model and a deficit accumulation approach. Cancer may contribute, at least additively, to the development of frailty, like any other comorbidity, rather than a global underlying condition of vulnerability.

Assessment of gait parameters and physical function in patients with advanced cancer participating in a 12-week exercise and nutrition programme: A controlled clinical trial

OBJECTIVE

Gait is a sensitive marker for functional declines commonly seen in patients treated for advanced cancer. We tested the effect of a combined exercise and nutrition programme on gait parameters of advanced-stage cancer patients using a novel wearable gait analysis system.

METHODS

Eighty patients were allocated to a control group with nutritional support or to an intervention group additionally receiving whole-body electromyostimulation (WB-EMS) training (2×/week). At baseline and after 12 weeks, physical function was assessed by a biosensor-based gait analysis during a six-minute walk test, a 30-s sit-to-stand test, a hand grip strength test, the Karnofsky Index and EORTC QLQ-C30 questionnaire. Body composition was measured by bioelectrical impedance analysis and inflammation by blood analysis.

RESULTS

Final analysis included 41 patients (56.1% male; 60.0 ± 13.0 years). After 12 weeks, the WB-EMS group showed higher stride length, gait velocity (p < .05), six-minute walking distance (p < .01), bodyweight and skeletal muscle mass, and emotional functioning (p < .05) compared with controls. Correlations between changes in gait and in body composition, physical function and inflammation were detected.

CONCLUSION

Whole-body electromyostimulation combined with nutrition may help to improve gait and functional status of cancer patients. Sensor-based mobile gait analysis objectively reflects patients' physical status and could support treatment decisions.

[Muscle mass measurement by DXA and MRI in non-human primates]

The global population is aging rapidly and, in Japan, the number of elderly has been steadily rising. It is important to shrink the gap between the average lifespan and the number of years people can expect to remain healthy. This links with improving the quality of life for the elderly and reducing social welfare spending. Maintaining motor function is believed to be a key to extending the number of years a person remains healthy, but recent years have seen a rise in locomotive syndrome. Decreases in muscle mass with age, and the deterioration in motor functions leads to sarcopenia. However, there is a dearth of medicines for increasing muscle mass or muscular strength. In this study, we used non-human primates (NHPs), which have similar anatomical features to humans and have advanced functional differentiation between the fore- and hindlimbs, to examine a highly accurate method of measuring muscle mass using Magnetic Resonance Imaging (MRI) and compared it to Dual Energy X-ray Absorptiometry (DXA) usually used in clinical settings. The results showed that both MRI and DXA provided high repeatability. Furthermore, correlation analysis between the amount of excised muscle for measurement and the results from MRI and DXA showed a high correlation at all sites examined, with the correlation coefficient higher for MRI than for DXA. We expect that the establishment of a highly accurate method for measurement of muscle mass using MRI and DXA will give impetus to the development of drugs that target muscle mass.

Optimization and In Vivo Profiling of a Refined Rat Model of Walker 256 Breast Cancer Cell-Induced Bone Pain Using Behavioral, Radiological, Histological, Immunohistochemical and Pharmacological Methods

In the majority of patients with advanced breast cancer, there is metastatic spread to bones resulting in pain. Clinically available drug treatments for alleviation of breast cancer-induced bone pain (BCIBP) often produce inadequate pain relief due to dose-limiting side-effects. A major impediment to the discovery of novel well-tolerated analgesic agents for the relief of pain due to bony metastases is the fact that most cancer-induced bone pain models in rodents relied on the systemic injection of cancer cells, causing widespread formation of cancer metastases and poor general animal health. Herein, we have established an optimized, clinically relevant Wistar Han female rat model of breast cancer induced bone pain which was characterized using behavioral assessments, radiology, histology, immunohistochemistry and pharmacological methods. In this model that is based on unilateral intra-tibial injection (ITI) of Walker 256 carcinoma cells, animals maintained good health for at least 66 days post-ITI. The temporal development of hindpaw hypersensitivity depended on the initial number of Walker 256 cells inoculated in the tibiae. Hindpaw hypersensitivity resolved after approximately 25 days, in the continued presence of bone tumors as evidenced by ex vivo histology, micro-computed tomography scans and immunohistochemical assessments of tibiae. A possible role for the endogenous opioid system as an internal factor mediating the self-resolving nature of BCIBP was identified based upon the observation that naloxone, a non-selective opioid antagonist, caused the re-emergence of hindpaw hypersensitivity. Bolus dose injections of morphine, gabapentin, amitriptyline and meloxicam all alleviated hindpaw hypersensitivity in a dose-dependent manner. This is a first systematic pharmacological profiling of this model by testing standard analgesic drugs from four important diverse classes, which are used to treat cancer induced bone pain in the clinical setting. Our refined rat model more closely mimics the pathophysiology of this condition in humans and hence is well-suited for probing the mechanisms underpinning breast cancer induced bone pain. In addition, the model may be suitable for efficacy profiling of new molecules from drug discovery programs with potential to be developed as novel agents for alleviation of intractable pain associated with disseminated breast cancer induced bony metastases.