Cancer pain physiology

Common Non-Rheumatic Medical Conditions Mimicking Fibromyalgia: A Simple Framework for Differential Diagnosis

Fibromyalgia (FM) is a chronic non-inflammatory disorder mainly characterized by widespread musculoskeletal pain, fatigue, sleep disturbances, and a constellation of other symptoms. For this reason, delineating a clear distinction between pure FM and FM-like picture attributable to other common diseases can be extremely challenging. Physicians must identify the most significant confounders in individual patients and implement an appropriate diagnostic workflow, carefully choosing a minimal (but sufficient) set of tests to be used for identifying the most plausible diseases in the specific case. This article discusses prevalent non-rheumatological conditions commonly observed in the general population that can manifest with clinical features similar to primary FM. Given their frequent inclusion in the differential diagnosis of FM patients, the focus will be on elucidating the distinctive clinical characteristics of each condition. Additionally, the most cost-effective and efficient diagnostic methodologies for accurately discerning these conditions will be examined.

Managing Severe Cancer Pain with Oxycodone/Naloxone Treatment: A Literature Review Update

Severe cancer pain substantially affects patients' quality of life, increasing the burden of the disease and reducing the disability-adjusted life years. Although opioid analgesics are effective, they may induce opioid-induced bowel dysfunction (OIBD). Oxycodone/naloxone combination therapy has emerged as a promising approach to mitigate opioid-induced constipation (OIC) while providing effective pain relief. This review provides an updated analysis of the literature of the last decade regarding the use of oxycodone/naloxone in the management of severe cancer pain. Through a comprehensive search of databases, studies focusing on the efficacy, safety, and patient experience of oxycodone/naloxone's prolonged release in severe cancer pain management were identified. Furthermore, the literature discusses the mechanism of action of naloxone in mitigating OIC without compromising opioid analgesia. Overall, the evidence suggests that oxycodone/naloxone combination therapy offers a valuable option for effectively managing severe cancer pain while minimizing opioid-induced constipation, thereby improving patients' quality of life. However, further research is needed to optimize dosing regimens, evaluate long-term safety, and assess patient outcomes in diverse cancer populations.

Efficacy and Safety of Ketamine to Treat Cancer Pain in Adult Patients: A Systematic Review

CONTEXT

Ketamine is a well-characterized anesthetic agent, and subanesthetic ketamine possesses analgesic effects in both acute and chronic pain.

OBJECTIVES

A systematic review was performed to ascertain the efficacy and safety of ketamine in treating pain for cancer patients.

METHODS

Eight databases were searched from the inception to March 20th, 2023 to obtain randomized controlled trials (RCTs) on ketamine for treating pain in cancer patients. Two reviewers independently screened studies, extracted the data and assessed the risk of bias of included studies; then, meta-analysis was performed by using Revman 5.3 software and Stata 14.0 software.

RESULTS

Thirty-five studies were included, involving 2279 patients with cancer pain. The results of meta-analysis showed that ketamine could significantly reduce pain intensity. Subgroup analysis revealed that, when compared with control group, ketamine decreased markedly visual analogue scale (VAS) scores in two days after the end of treatment with ketamine, and ketamine administrated by patient controlled epidural analgesia (PCEA) was effective. Meanwhile, ketamine could significantly reduce the number of patient-controlled analgesia (PCA) compressions within 24 hours and morphine dosage. Ketamine could not decrease Ramsay sedation score. Additionally, the adverse events significantly decreased in the ketamine group, including nausea and vomiting, constipation, pruritus, lethargy, uroschesis, hallucination, and respiratory depression. In addition, compared with the control group, ketamine could reduce Hamilton depression scale (HAMD) score and relieve depressive symptoms.

CONCLUSION

Ketamine may be used as an effective therapy to relieve cancer pain. However, more rigorously designed RCTs with larger sample sizes are required to verify the above conclusions.

Methadone prescribed as an analgesic by a specialist palliative medicine team in an acute hospital inpatient setting: retrospective study

Emerging evidence suggests that methadone has a specific role in the management of treatment resistant cancer-related pain.

OBJECTIVES

To investigate the utilisation pattern, safety and efficacy of methadone prescribed as an analgesic for the management of complex cancer-related pain in an acute hospital inpatient setting.

METHODS

A retrospective longitudinal observational study of patients prescribed methadone as an analgesic between April 2020 and July 2021 was performed.Changes in coprescribed baseline opioid, use of breakthrough opioid analgesic, patient rated pain scores and adverse side effects were analysed.

RESULTS

16 patients with complex cancer-related treatment resistant pain who were prescribed methadone were included in the study. Of the 16 patients, 14 patients had metastatic disease. Pain was classified in 14 patients as mixed nociceptive-neuropathic and in 2 patients as neuropathic. 13 patients were coprescribed methadone with a pre-established opioid. Methadone was associated with a statistically significant decrease in both opioid breakthrough analgesic by 61%±28% (p<0.001), and coprescribed opioid by 17%±12% (p=0.015). Patient rated pain scores were also significantly decreased (p<0.001).

CONCLUSION

Methadone appears to have a specific role in the management of complex cancer pain, neuropathic pain, opioid-tolerance and opioid-induced hyperalgesia, which may be attributable to N-methyl-D-aspartate receptor antagonism.

Opioid Use in Surgical Management in Musculoskeletal Oncology

BACKGROUND

Opioid prescribing in the context of orthopaedic surgery has been recognized as having a critical role in the ongoing opioid epidemic. Given the negative consequences of chronic opioid use, great efforts have been made to reduce both preoperative and postoperative opioid prescribing and consumption in orthopaedic surgery. Musculoskeletal oncology patients represent a unique subset of patients, and there is a paucity of data evaluating perioperative opioid consumption and the risk for chronic use. The objective of the present study was to describe opioid consumption patterns and evaluate predictors of chronic opioid use in musculoskeletal oncology patients undergoing limb-salvage surgery and endoprosthetic reconstruction.

METHODS

The present study was a secondary analysis of the recently completed PARITY (Prophylactic Antibiotic Regimens in Tumor Surgery) trial and included musculoskeletal oncology patients undergoing lower-extremity endoprosthetic reconstruction. The primary outcome was the incidence of opioid consumption over the study period. A multivariate binomial logistic regression model was created to explore predictors of chronic opioid consumption at 1 year postoperatively.

RESULTS

Overall, 193 (33.6%) of 575 patients were consuming opioids preoperatively. Postoperatively, the number of patients consuming opioids was 82 (16.7%) of 492 at 3 months, 37 (8%) of 460 patients at 6 months, and 28 (6.6%) of 425 patients at 1 year. Of patients consuming opioids preoperatively, 12 (10.2%) of 118 had continued to consume opioids at 1 year postoperatively. The adjusted regression model found that only surgery for metastatic bone disease was predictive of chronic opioid use (odds ratio, 4.90; 95% confidence interval, 1.54 to 15.40; p = 0.007). Preoperative opioid consumption, older age, sex, longer surgical times, reoperation rates, and country of origin were not predictive of chronic use.

CONCLUSIONS

Despite a high prevalence of preoperative opioid use, an invasive surgical procedure, and a high rate of reoperation, few patients had continued to consume opioids at 1 year postoperatively. The presence of metastases was associated with chronic opioid use. These results are a substantial departure from the existing orthopaedic literature evaluating other patient populations, and they suggest that specific prescribing guidelines are warranted for musculoskeletal oncology patients.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Efficacy and Security of Tetrodotoxin in the Treatment of Cancer-Related Pain: Systematic Review and Meta-Analysis

The pharmacological treatment of cancer-related pain is unsatisfactory. Tetrodotoxin (TTX) has shown analgesia in preclinical models and clinical trials, but its clinical efficacy and safety have not been quantified. For this reason, our aim was to perform a systematic review and meta-analysis of the clinical evidence that was available. A systematic literature search was conducted in four electronic databases (Medline, Web of Science, Scopus, and ClinicalTrials.gov) up to 1 March 2023 in order to identify published clinical studies evaluating the efficacy and security of TTX in patients with cancer-related pain, including chemotherapy-induced neuropathic pain. Five articles were selected, three of which were randomized controlled trials (RCTs). The number of responders to the primary outcome (≥30% improvement in the mean pain intensity) and those suffering adverse events in the intervention and placebo groups were used to calculate effect sizes using the log odds ratio. The meta-analysis showed that TTX significantly increased the number of responders (mean = 0.68; 95% CI: 0.19-1.16, p = 0.0065) and the number of patients suffering non-severe adverse events (mean = 1.13; 95% CI: 0.31-1.95, p = 0.0068). However, TTX did not increase the risk of suffering serious adverse events (mean = 0.75; 95% CI: -0.43-1.93, p = 0.2154). In conclusion, TTX showed robust analgesic efficacy but also increased the risk of suffering non-severe adverse events. These results should be confirmed in further clinical trials with higher numbers of patients.

Differences and Similarities in Spontaneous Activity Between Animal Models of Cancer-Induced Pain and Neuropathic Pain

Background

Clinical data on cancer-induced pain (CIP) demonstrate widespread changes in sensory function. It is characterized in humans not only by stimulus-invoked pain, but also by spontaneous pain. In our previous studies in an animal model of CIP, we observed changes in intrinsic membrane properties and excitability of dorsal root ganglion (DRG) sensory neurons corresponding to mechanical allodynia and hyperalgesia, of which abnormal activities of Aβ-fiber sensory neurons are consistent in a rat model of peripheral neuropathic pain (NEP).

Objective

To investigate whether there are related peripheral neural mechanisms between the CIP and NEP models of spontaneous pain, we compared the electrophysiological properties of DRG sensory neurons at 2–3 weeks after CIP and NEP model induction.

Methods

CIP models were induced with metastasis tumour-1 rat breast cancer cells implanted into the distal epiphysis of the femur. NEP models were induced with a polyethylene cuff implanted around the sciatic nerve. Spontaneous pain in animals is measured by spontaneous foot lifting (SFL). After measurement of SFL, the animals were prepared for electrophysiological recordings of spontaneous activity (SA) in DRG neurons in vivo.

Results

Our data showed that SFL and SA occurred in both models. The proportion of SFL and SA of C-fiber sensory neurons in CIP was more significantly increased than in NEP models. There was no difference in duration of SFL and the rate of SA between the two models. The duration of SFL is related to the rate of SA in C-fiber in both models.

Conclusion

Thus, SFL may result from SA activity in C-fiber neurons in CIP and NEP rats. The differences and similarities in spontaneous pain between CIP and NEP rats is related to the proportion and rate of SA in C-fibers, respectively.

The Use of Low-Dose Methadone as Add-On to Ongoing Opioid Treatment in Palliative Cancer Care-An Underrated Treatment?

The aim of this review is to summarize the current knowledge of low-dose methadone treatment in palliative cancer care. In Sweden, methadone is quite common in specialized palliative care, where almost a tenth of patients are prescribed this drug. Negative attitudes towards methadone do not seem to prevent it from being used for pain management, and by starting with low doses and then increasing slowly and gradually, methadone can apparently be introduced safely. It is still uncertain whether methadone has a better analgesic effect than other opioids. However, for pain relief in cancer patients with severe and complex cancer-related pain, NMDA receptor inhibition with methadone may, in selected cases, be an attractive alternative, especially in the form of low-dose supplements to other ongoing opioids. Due to long half-life and complex metabolism, the use of methadone requires an experienced physician and solid follow-up. Continuous administration of opioids, including low-dose methadone, has been proven effective and safe in reducing pain in dying patients without increasing the risk of confusion, regardless of age.

A Survey of Knowledge and Barriers of Healthcare Professionals toward Opioid Analgesics in Cancer Pain Management

PURPOSE

Pain is among the most frequent and troubling symptoms in cancer patients. Despite the availability of updated treatment guidelines and effective pharmacological therapies, undertreatment of cancer pain remains a global problem. Opioids are the mainstay analgesics to treat moderate-to-severe cancer pain. The goal of this study was to assess the knowledge and barriers towards opioid analgesics for cancer pain management among healthcare professionals in Oncology Units in Jordan.

METHODS

A structured questionnaire was administered to healthcare professionals (consultant doctors, resident doctors, pharmacists, and nurses) at three Oncology Units in a cross-sectional study design.

RESULTS

A total of 201 healthcare professionals completed the questionnaire. The average age was 34.8 ± 8.1 years (range 23-58) and 49.3% of respondents were nurses. The mean score for the knowledge of opioids was 12.5 ± 3.2 out of 24 points (range 2-20). An acceptable level of knowledge was observed in 50.7% of participants, while 49.3% had poor knowledge. Knowledge items mostly answered incorrectly were related to opioid administration, pharmacology, dosing, adverse events, rotation, and toxicity. Knowledge scores were significantly higher for consultant doctors compared to pharmacists and nurses (p=0.016 and p < 0.001, respectively). Healthcare professionals who handled opioid analgesics had significantly higher mean knowledge scores than those who did not (p=0.012). Linear regression analysis revealed that being a consultant physician has an independent, statistically significant association with higher knowledge scores. Among perceived barriers to using opioids, fear of addiction by patients was the most frequently reported barrier by respondents (79.6%). Other highly recognized barriers were fear of adverse effects by patients (67.2%) and lack of training programs on opioid dosing and monitoring (63.7%).

CONCLUSIONS

This study revealed major gaps in the knowledge of opioids and pain management among healthcare professionals. There is an urgent need for developing innovative interventions to improve the knowledge of opioid analgesics and the understanding of pain management guidelines among healthcare professionals in Jordan.

The preoperative machine learning algorithm for extremity metastatic disease can predict 90-day and 1-year survival: An external validation study

BACKGROUND

The prediction of survival is valuable to optimize treatment of metastatic long-bone disease. The Skeletal Oncology Research Group (SORG) machine-learning (ML) algorithm has been previously developed and internally validated. The purpose of this study was to determine if the SORG ML algorithm accurately predicts 90-day and 1-year survival in an external metastatic long-bone disease patient cohort.

METHODS

A retrospective review of 264 patients who underwent surgery for long-bone metastases between 2003 and 2019 was performed. Variables used in the stochastic gradient boosting SORG algorithm were age, sex, primary tumor type, visceral/brain metastases, systemic therapy, and 10 preoperative laboratory values. Model performance was calculated by discrimination, calibration, and overall performance.

RESULTS

The SORG ML algorithms retained good discriminative ability (area under the cure [AUC]: 0.83; 95% confidence interval [CI]: 0.76-0.88 for 90-day mortality and AUC: 0.84; 95% CI: 0.79-0.88 for 1-year mortality), calibration, overall performance, and decision curve analysis.

CONCLUSION

The previously developed ML algorithms demonstrated good performance in the current study, thereby providing external validation. The models were incorporated into an accessible application (https://sorg-apps.shinyapps.io/extremitymetssurvival/) that may be freely utilized by clinicians in helping predict survival for individual patients and assist in informative decision-making discussion before operative management of long bone metastatic lesions.

Tetrodotoxin: A New Strategy to Treat Visceral Pain?

Visceral pain is one of the most common symptoms associated with functional gastrointestinal (GI) disorders. Although the origin of these symptoms has not been clearly defined, the implication of both the central and peripheral nervous systems in visceral hypersensitivity is well established. The role of several pathways in visceral nociception has been explored, as well as the influence of specific receptors on afferent neurons, such as voltage-gated sodium channels (VGSCs). VGSCs initiate action potentials and dysfunction of these channels has recently been associated with painful GI conditions. Current treatments for visceral pain generally involve opioid based drugs, which are associated with important side-effects and a loss of effectiveness or tolerance. Hence, efforts have been intensified to find new, more effective and longer-lasting therapies. The implication of VGSCs in visceral hypersensitivity has drawn attention to tetrodotoxin (TTX), a relatively selective sodium channel blocker, as a possible and promising molecule to treat visceral pain and related diseases. As such, here we will review the latest information regarding this toxin that is relevant to the treatment of visceral pain and the possible advantages that it may offer relative to other treatments, alone or in combination.

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.

Inferior Hypogastric Block for the Treatment of Chronic Pelvic Pain

Context

Pelvic pain is described as pain originating from the visceral or somatic system localizing to the pelvis, the anterior abdominal wall at the level of or below the umbilicus, lumbosacral back in either men or women.

Evidence Acquisition

Narrative review.

Results

Chronic pelvic pain can be a complex disorder that may involve multiple systems such as urogynecological, gastrointestinal, neuromusculoskeletal, and psychosocial systems. The etiopathogenesis for chronic pain remains unknown for many patients. For achieving optimal patient management, a multimodal and individualized assessment of each patient is the best strategy.

Conclusions

There are non-pharmacologic treatments as well as pharmacologic treatments. In addition to these treatment options, inferior hypogastric plexus block is a promising treatment modality.

Non-opioid Analgesics and Emerging Therapies

Pain is a common and debilitating symptom of cancer. Cancer-related pain can occur at any point along the continuum from diagnosis to treatment to survivorship¹. A systematic review published in 2016 estimated the prevalence of cancer pain to be 55% in those undergoing antineoplastic treatment, 66.4% in advanced cancer, and 39.3% in the post-treatment population. Thirty-eight percent of cancer patients in this pooled analysis experienced moderate to severe pain².

Bone metastasis: mechanisms, therapies, and biomarkers

Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability) that negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process: long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described, and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes, and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.

The Effect of Heat Shock Protein 90 Inhibitor on Pain in Cancer Patients: A Systematic Review and Meta-Analysis

Background and objectives: Heat shock protein 90 (Hsp90) is a molecular chaperone that plays an essential role in tumor growth. Numerous Hsp90 inhibitors have been discovered and tested in preclinical and clinical trials. Recently, several preclinical studies have demonstrated that Hsp90 inhibitors could modulate pain sensitization. However, no studies have evaluated the impact of Hsp90 inhibitors on pain in the patients. This study aims to summarize the pain events reported in clinical trials assessing Hsp90 inhibitors and to determine the effect of Hsp90 inhibitors on pain in patients. Materials and Methods: We searched PubMed, EBSCOhost, and clinicaltrials.gov for Hsp90 inhibitor clinical trials. The pain-related adverse events were summarized. Meta-analysis was performed using the data reported in randomized controlled trials. Results: We identified 90 clinical trials that reported pain as an adverse effect, including 5 randomized controlled trials. The most common types of pain reported in all trials included headache, abdominal pain, and back pain. The meta-analysis showed that Hsp90 inhibitors increased the risk of abdominal pain significantly and appeared to increase the risk for back pain. Conclusions: In conclusion, Hsp90 inhibitor treatment could potentially increase the risk of pain. However, the meta-analysis demonstrated only moderate evidence for the connection between Hsp90 inhibitor and pain.

Determinants of pain in advanced HCC patients recieving hepatic artery infusion chemotherapy

Purpose Hepatic arterial infusion chemotherapy (HAIC) is one of the options to treat unresectable hepatocellular carcinoma (HCC). The majority of HCC patients suffer great pain in the course of HAIC treatment. To improve the quality of life and the efficacy of HAIC treatment, the causes of pain, the choice of an analgesic regimen, and the relationship between pain and prognosis of HCC were analyzed. Methods A total of 376 HCC patients under HAIC in our hospital were recriuted between March 2017 and September 2019. Multivariate linear regression analysis (stepwise) was used to calculate the potential factors related to the severe pain in HCC patients under HAIC. Analgesics treatments were carried out based on the results of the visual analogue scale (VAS) score which was used to evaluate the pain. Results The mean value of the VAS score is 3.604, which indicates that the pain in most patients is mild and endurable. Intra-arterial lidocaine injection is an effective method in most patients (96%, 361 of 376), and the total score of VAS is reduced from 1355 to 195 following lidocaine injection. Multivariate analysis suggestes that oxaliplatin (OXA) preparation time, hepatic artery diameter and OXA manufacturers (R² = 0.859) are influential factors for pain scores. Conclusion This study demonstrates an effective way to systematically assess and ease pain in HCC patients with HAIC treatment. OXA preparation time, hepatic artery diameter, and OXA manufacturers are the potential influencing factors for pain. This work presented here will provide a detailed understanding of the clinical application of HAIC in advanced HCC patients.

TRPA1 as a therapeutic target for nociceptive pain

Introduction

Chronic pain affects approximatively 30–50% of the population globally. Pathologies such as migraine, diabetic neuropathy, nerve injury and treatment with chemotherapeutic agents, can induce chronic pain. Members of the transient receptor potential (TRP) channels, including the TRP ankyrin 1 (TRPA1), have a major role in pain.

Areas covered

We focus on TRPA1 as a therapeutic target for pain relief. The structure, localization, and activation of the channel and its implication in different pathways to signal pain are described. This paper underlines the role of pharmacological interventions on TRPA1 to reduce pain in numerous pain conditions. We conducted a literature search in PubMed up to and including July 2020.

Expert opinion

Our understanding of the molecular mechanisms underlying the sensitization of central and peripheral nociceptive pathways is limited. Preclinical evidence indicates that, in murine models of pain diseases, numerous mechanisms converge on the pathway that encompasses oxidative stress and Schwann cell TRPA1 to sustain chronic pain. Programs to identify and develop treatments to attenuate TRPA1-mediated chronic pain have emerged from this knowledge. Antagonists explored as a novel class of analgesics have a new and promising target in the TRPA1 expressed by peripheral glial cells.

The biology and engineered modeling strategies of cancer-nerve crosstalk

A recent finding critical to cancer aggravation is the interaction between cancer cells and nerves. There exist two main modes of cancer-nerve interaction: perineural invasion (PNI) and tumor innervation. PNI occurs when cancer cells infiltrate the adjacent nerves, and its relative opposite, tumor innervation, occurs when axons extend into tumor bodies. Like most cancer studies, these crosstalk interactions have mostly been observed in patient samples and animal models at this point, making it difficult to understand the mechanisms in a controlled manner. As such, in recent years in vitro studies have emerged that have helped identify various microenvironmental factors responsible for cancer-nerve crosstalk, including but not limited to neurotrophic factors, neurotransmitters, chemokines, cancer-derived exosomes, and Schwann cells. The versatility of in vitro systems warrants continuous development to increase physiological relevance to study PNI and tumor innervation, for example by utilizing biomimetic three-dimensional (3D) culture systems. Despite the wealth of 3D in vitro cancer models, comparatively there exists a lack of 3D in vitro models of nerve, PNI, and tumor innervation. Native-like 3D in vitro models of cancer-nerve interactions may further help develop therapeutic strategies to curb nerve-mediated cancer aggravation. As such, we provide an overview of the key players of cancer-nerve crosstalk and current in vitro models of the crosstalk, as well as cancer and nerve models. We also discuss a few future directions in cancer-nerve crosstalk research.

The impact of bone cancer on the peripheral encoding of mechanical pressure stimuli

Skeletal metastases are frequently accompanied by chronic pain that is mechanoceptive in nature. Mechanistically, cancer-induced bone pain (CIBP) is mediated by peripheral sensory neurons innervating the cancerous site, the cell bodies of which are housed in the dorsal root ganglia (DRG). How these somatosensory neurons encode sensory information in CIBP remains only partly explained. Using a validated rat model, we first confirmed cortical bone destruction in CIBP but not sham-operated rats (day 14 after surgery, designated "late"-stage bone cancer). This occurred with behavioural mechanical hypersensitivity (Kruskal-Wallis H for independent samples; CIBP vs sham-operated, day 14; P < 0.0001). Next, hypothesising that the proportion and phenotype of primary afferents would be altered in the disease state, dorsal root ganglia in vivo imaging of genetically encoded calcium indicators and Markov Cluster Analysis were used to analyse 1748 late-stage CIBP (n = 10) and 757 sham-operated (n = 9), neurons. Distinct clusters of responses to peripheral stimuli were revealed. In CIBP rats, upon knee compression of the leg ipsilateral to the tumour, (1) 3 times as many sensory afferents responded (repeated-measures analysis of variance: P < 0.0001 [vs sham]); (2) there were significantly more small neurons responding (Kruskal-Wallis for independent samples (vs sham): P < 0.0001); and (3) approximately 13% of traced tibial cavity afferents responded (no difference observed between CIBP and sham-operated animals). We conclude that an increased sensory afferent response is present in CIBP rats, and this is likely to reflect afferent recruitment from outside of the bone rather than increased intraosseous afferent activity.

Analgesic efficacy of nefopam for cancer pain: a randomized controlled study

Background: Nefopam is a non-opioid, non-steroidal, central acting drug used effectively for postoperative pain. The efficacy of nefopam for cancer pain remains unclear. We aimed to evaluate the analgesic efficacy of nefopam for cancer pain in a randomized controlled trial. Methods: Patients with moderate to severe cancer pain (n=40) were randomly divided into two groups. The nefopam group (n=20) received three 20 mg doses of nefopam every 8 hours. The placebo group (n=20) received normal saline. Intravenous patient-controlled analgesia with morphine was given for breakthrough pain for 48 hours. The primary outcome was significant pain reduction. Secondary outcomes were morphine consumption over 48 hours and incidence of side effects. Results: The nefopam group showed pain reduction at 12 hours (65% of patients), 24 hours (80%), 36 hours (85%), and 48 hours (65%). The placebo group showed pain reduction at 12 hours (70%), 24 hours (75%), 36 hours (80%), and 48 hours (60%). However, there were no statistically significant differences between the groups (p>0.05). The median dosage of morphine consumption in 48 hours was lower in the nefopam group (25.5 mg) compared with the placebo group (37 mg), but this was not statistically significant (p=0.499). There were no statistically significant differences in blood pressure and heart rate between the groups. Side effects in both groups were comparable. Conclusions: At dosage of 60 mg in 24 hours, nefopam did not provide significant pain reduction in moderate to severe cancer pain patients. However, there was a trend of reduced opioid consumption. Further studies with larger sample sizes, longer duration, or higher doses of nefopam are warranted. Registration: Thai Clinical Trail Registry (TCTR) ID TCTR20181016001; registered on 12 October 2018.

Methadone in Swedish specialized palliative care-Is it the magic bullet in complex cancer-related pain?

CONTEXT

Despite being associated with dependence and social stigma, methadone is a potential end-of-life option in complex cancer pain.

OBJECTIVES

To explore attitudes and opinions about methadone and its potential role and current use in complex end-of-life pain.

METHODS

Semi-structured interviews (n = 30) with physicians in specialized palliative care, transcribed and analyzed with conventional qualitative content analysis.

RESULTS

According to the physicians, patients and relatives expressed unexpectedly few negative attitudes, not affecting methadone's use as an analgesic. Complex pain in bone-metastatic cancer of the prostate, breast and kidney, as well as pancreatic cancer and sarcomas were recurrent suggestions of appropriate indications. Most of the informants stated that they applied a mechanism-based treatment and mainly prescribed low-dose methadone as an add-on to an existing opioid therapy to benefit from methadone´s proposed NMDA-receptor inhibiting properties, e.g. in cases with reduced opioid sensitivity. Despite its complex pharmacokinetics with a long half-life, most informants expressed defined strategies to avoid side-effects such as respiratory depression, especially when initiating treatment in the home-care setting. While many palliative care physicians expressed an overly enthusiastic attitude, others stressed the risks of overconfidence, low precision in use, and overlooked treatment options. Besides the obvious physical pain-relieving effects, they stated that effective pain relief could result in a reduced workload and emotional empowerment, both for physicians and staff.

CONCLUSION

Methadone, especially in the form of low-dose add-on to other opioids is widely advocated in Swedish specialized palliative care as a practical and safe method with rapid onset in complex pain situations at the end of life.

Malignant Transformation of a Canine Papillomavirus Type 1-Induced Persistent Oral Papilloma in a 3-Year-Old Dog

This case report describes a rare case of a persistent canine papillomavirus type 1 (CPV-1)-induced oral papilloma that underwent malignant transformation into an oral squamous cell carcinoma (OSCC) in a 3-year-old Labrador retriever cross. Initially, the patient had multiple and multifocal verrucous lesions populating the oral cavity exclusively. The papillomas persisted despite multiple surgical ablations, azithromycin, interferon α-2b, alternative medicines, and off-label drug use of an immunostimulant. After 1 year and 6 months, an aggressive lesion developed at the level of the left mandibular first molar (309) and progressed to a well-differentiated invasive OSCC. The presence of CPV-1 DNA in the OSCC, and the known oncogenic abilities of CPV-1, suggests that this virus might have played a significant role in the emergence of the OSCC that ultimately led to the patient's euthanasia due to poor quality of life. This is the first well-documented case where OSCC has developed from an oral papilloma caused by CPV-1 in which the presence of coinfection by another papillomavirus was excluded by multiple polymerase chain reaction tests using various primers.

A cross-sectional, comparative, syndromic description of oncological mixed pain in Medical Oncology units in Spain

OBJECTIVE

The reason cancer pain remains prevalent and hard to classify may be partially explained by the failure to identify neuropathic mechanisms. The objective of this research was to identify the syndromes of cancer pain that may be particularly hard to manage due to their mixed pathophysiology.

DESIGN

A series of 384 patients who had cancer of any type, at any stage, and suffered from chronic pain (symptom onset > 3 months) were assessed during a routine return visit in Spain. Medical oncologists indicated the presence and pathophysiology of 33 predefined pain syndromes on a per-patient basis. This information was then measured against clinical, psychosocial, and health care-related data to determine which syndromes pose particular challenges.

RESULTS

The mean (standard deviation) age of patients was 61.6 (12.6) years, 49.7% were women. Most (82%) had advanced metastatic disease, 68.7% were on second-line or palliative therapies. The worst syndrome was nociceptive, pure neuropathic, and mixed in 34.6, 26.9, and 38.6% of patients, respectively. Any syndrome could be of mixed pathophysiology. Only 10 syndromes were common (≥ 5% of patients). Syndromes related to malignant bone pain and involvement of chest wall structures were the most frequent. Certain syndromes (including tumor-related bone pain, chemotherapy-induced peripheral neuropathies, paraneoplastic pain syndromes, and malignant neuralgias or injury to cranial nerves) can be particularly challenging when they have a mixed pathophysiology, because the neuropathic component is rarely or unevenly considered.

CONCLUSIONS

Virtually all cancer pain syndromes can present mixed pathophysiology. Certain syndromes can include neuropathic components that are frequently overlooked.

Mechanisms Underlying Bone and Joint Pain

PURPOSE OF REVIEW

The goal of this review is to provide a broad overview of the current understanding of mechanisms underlying bone and joint pain.

RECENT FINDINGS

Bone or joint pathology is generally accompanied by local release of pro-inflammatory cytokines, growth factors, and neurotransmitters that activate and sensitize sensory nerves resulting in an amplified pain signal. Modulation of the pain signal within the spinal cord and brain that result in net increased facilitation is proposed to contribute to the development of chronic pain. Great strides have been made in our understanding of mechanisms underlying bone and joint pain that will guide development of improved therapeutic options for these patients. Continued research is required for improved understanding of mechanistic differences driving different components of bone and/or joint pain such as movement related pain compared to persistent background pain. Advances will guide development of more individualized and comprehensive therapeutic options.

Tetrodotoxin for Moderate to Severe Cancer-Related Pain: A Multicentre, Randomized, Double-Blind, Placebo-Controlled, Parallel-Design Trial

Objective

This study evaluated subcutaneous injections of tetrodotoxin (TTX) for the treatment of moderate to severe, inadequately controlled cancer-related pain.

Methods

Eligible patients were randomized to receive TTX (30 μg) or placebo subcutaneously twice daily for four consecutive days. Efficacy was assessed using pain and composite endpoints (including pain and quality of life measures), and safety was evaluated using standard measures.

Results

165 patients were enrolled at 19 sites in Canada, Australia, and New Zealand, with 149 patients in the primary analysis “intent-to-treat” population. The primary analysis supports a clinical benefit of TTX over placebo based on the pain endpoint alone with a clinically significant estimated effect size of 16.2% (p = 0.0460). The p value was nominally statistically significant after prespecified (Bonferroni Holm) adjustment for the two primary endpoints but not at the prespecified two-sided 5% level. The mean duration of analgesic response was 56.7 days (TTX) and 9.9 days (placebo). Most common adverse events were nausea, dizziness, and oral numbness or tingling and were generally mild to moderate and transient.

Conclusions

Although underpowered, this study demonstrates a clinically important analgesic signal. TTX may provide clinically meaningful analgesia for patients who have persistent moderate to severe cancer pain despite best analgesic care. This clinical study is registered with ClinicalTrials.gov (NCT00725114).

Bone Pain and Muscle Weakness in Cancer Patients

PURPOSE OF REVIEW

In this article, we will discuss the current understanding of bone pain and muscle weakness in cancer patients. We will describe the underlying physiology and mechanisms of cancer-induced bone pain (CIBP) and cancer-induced muscle wasting (CIMW), as well as current methods of diagnosis and treatment. We will discuss future therapies and research directions to help patients with these problems.

RECENT FINDINGS

There are several pharmacologic therapies that are currently in preclinical and clinical testing that appear to be promising adjuncts to current CIBP and CIMW therapies. Such therapies include resiniferitoxin, which is a targeted inhibitor of noceciptive nerve fibers, and selective androgen receptor modulators, which show promise in increasing lean mass. CIBP and CIMW are significant causes of morbidity in affected patients. Current management is mostly palliative; however, targeted therapies are poised to revolutionize how these problems are treated.