Chemotherapy-Induced Peripheral Neuropathy (CIPN): A Narrative Review and Proposed Theoretical Model

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating symptom experienced by cancer survivors. Despite the burden of CIPN-related symptoms, interventions remain limited.

OBJECTIVES

This narrative review seeks to propose a framework for CIPN predisposing, precipitating, and perpetuating factors (3Ps), which will provide a foundation for future research and clinical interventions aimed at mitigating CIPN-related symptoms and morbidity.

METHODS

A comprehensive literature search was performed using PubMed, guided by keywords related to "chemotherapy-induced peripheral neuropathy." Studies were limited to those with full text available in English.

RESULTS

Predisposing factors outlined in this framework, such as older age and comorbid conditions, can be used to identify patients who have a higher risk of developing CIPN. The major precipitating factor of CIPN is the delivery of chemotherapy to peripheral nerves, which may be mitigated via cryotherapy or compression therapy during chemotherapy. Perpetuating factors can offer insight into psychological, cognitive, and behavioral modifications that could be treatment targets for CIPN management.

CONCLUSION

The proposed 3P model can guide the development of effective interventions for CIPN by suggesting modifiable psychological and behavioral treatment targets that may mitigate the impact of CIPN for cancer patients.

Paradoxical heat sensation as a manifestation of thermal hypesthesia: a study of 1090 patients with lesions of the somatosensory system

ABSTRACT

Paradoxical heat sensation (PHS) is the perception of warmth when the skin is cooled. Paradoxical heat sensation rarely occurs in healthy individuals but more frequently in patients suffering from lesions or disease of the peripheral or central nervous system. To further understand mechanisms and epidemiology of PHS, we evaluated the occurrence of PHS in relation to disease aetiology, pain levels, quantitative sensory testing parameters, and Neuropathic Pain Symptom Inventory (NPSI) items in patients with nervous system lesions. Data of 1090 patients, including NPSI scores from 404 patients, were included in the analysis. We tested 11 quantitative sensory testing parameters for thermal and mechanical detection and pain thresholds, and 10 NPSI items in a multivariate generalised linear model with PHS, aetiology, and pain (yes or no) as fixed effects. In total, 30% of the neuropathic patients reported PHS in contrast to 2% of healthy individuals. The frequency of PHS was not linked to the presence or intensity of pain. Paradoxical heat sensation was more frequent in patients living with polyneuropathy compared with central or unilateral peripheral nerve lesions. Patients who reported PHS demonstrated significantly lower sensitivity to thermal perception, with lower sensitivity to normally painful heat and cold stimuli. Neuropathic Pain Symptom Inventory scores were lower for burning and electric shock-like pain quality for patients with PHS. Our findings suggest that PHS is associated with loss of small thermosensory fibre function normally involved in cold and warm perception. Clinically, presence of PHS could help screening for loss of small fibre function as it is straightforward to measure or self-reported by patients.

It is one or the other: No overlap between healthy individuals perceiving thermal grill illusion or paradoxical heat sensation

Paradoxical heat sensation (PHS) and the thermal grill illusion (TGI) are both related to the perception of warmth or heat from innocuous cold stimuli. Despite being described as similar perceptual phenomena, recent findings suggested that PHS is common in neuropathy and related to sensory loss, while TGI is more frequently observed in healthy individuals. To clarify the relationship between these two phenomena, we conducted a study in a cohort of healthy individuals to investigate the association between PHS and TGI. We examined the somatosensory profiles of 60 healthy participants (34 females, median age 25 years) using the quantitative sensory testing (QST) protocol from the German Research Network on Neuropathic Pain. The number of PHS was measured using a modified thermal sensory limen (TSL) procedure where the skin was transiently pre-warmed, or pre-cooled before the PHS measure. This procedure also included a control condition with a pre-temperature of 32 °C. The number of TGI responses was quantified during simultaneous application of warm and cold innocuous stimuli. All participants had normal thermal and mechanical thresholds compared to the reference values from the QST protocol. Only two participants experienced PHS during the QST procedure. In the modified TSL procedure, we found no statistically significant differences in the number of participants reporting PHS in the control condition (N = 6) vs. pre-warming (N = 3; min = 35.7 °C, max = 43.5 °C) and pre-cooling (N = 4, min = 15.0 °C, max = 28.8 °C) conditions. Fourteen participants experienced TGI, and only one participant reported both TGI and PHS. Individuals with TGI had normal or even increased thermal sensation compared to individuals without TGI. Our findings demonstrate a clear distinction between individuals experiencing PHS or TGI, as there was no overlap observed when using identical warm and cold temperatures that were alternated either temporally or spatially. While PHS was previously related to sensory loss, our study revealed that TGI is associated with normal thermal sensitivity. This suggests that an efficient thermal sensory function is essential in generating the illusory sensation of pain of the TGI.

Management of treatment-related sequelae following colorectal cancer

AIM

Colorectal cancer survivors are one of the most rapidly growing groups of patients living with and beyond cancer. In a national multidisciplinary setting, we have examined the extent of late treatment-related sequelae in colorectal cancer survivors and present the scientific evidence for management of these conditions in this patient category with the aim of facilitating identification and treatment.

METHOD

A systematic search for existing guidelines and relevant studies was performed across 16 and 4 databases, respectively, from inception to 2021. This yielded 13 guidelines and 886 abstracts, of which 188 were included in the finalized guideline (231 included for full text review). Secondarily, bibliographies were cross-referenced and 53 additional articles were included.

RESULTS

Symptoms have been divided into overall categories including psychosocial, bowel-related, urinary, sexual (male and female), pain/neuropathy and fatigue symptoms or complaints that are examined individually. Merging and grading of data resulted in 22 recommendations and 42 management strategies across categories. Recommendations are of a more general character, whereas management strategies provide more practical advice suited for initiation on site before referral to specialized units.

CONCLUSION

Treatment-related sequelae in colorectal cancer survivors are common and attention needs to be focused on identifying patients with unmet treatment needs and the development of evidence-based treatment algorithms.

Efficacy of Acupuncture Combined with Patient-Controlled Analgesia in the Treatment of Acute Pain after Back Surgery: A Meta-Analysis

Objectives. Acupuncture is used worldwide to relieve both acute and chronic pain. Patient-controlled analgesia (PCA) is also frequently used for postoperative pain relief. However, there are few meta-analyses of the efficacy of acupuncture with PCA in reducing acute postoperative pain. This meta-analysis aimed to assess the effectiveness of acupuncture with PCA in relieving acute pain after back surgery. Methods. We searched seven databases (Cochrane Library, Web of Science, PubMed, China National Knowledge Infrastructure (CNKI), Wanfang database, Chongqing VIP (VIP), and Chinese BioMedical Literature Database (CBM)-from 1949 until now) without language restrictions for randomized controlled trials, including patients undergoing back surgery and receiving PCA alone or treated with acupuncture/sham acupuncture + PCA for pain relief. This meta-analysis assessed pain intensity, with visual analogue scale (VAS) score and postoperative opioid dosage as primary outcomes. Results. A total of 12 randomized controlled trials (n = 904) met the inclusion criteria. Compared with the control group (standard mean difference (SMD) = ‒0.42, 95% CI = ‒0.60 to ‒0.25, $P<0.01$ ) or sham acupuncture + PCA (SMD = ‒0.7, 95% CI = ‒0.94 to ‒0.46, $P<0.01$ ), acupuncture + PCA treatment reduced the VAS score in patients after back surgery. Acupuncture + PCA decreased the use of opioids after surgery compared to sham acupuncture + PCA (SMD = −0.35, 95% CI = ‒0.63 to ‒0.07, $P=0.01$ ) or control group (SMD = ‒0.82, 95% CI = ‒1.03 to ‒0.61, $P<0.01$ ). Furthermore, the use of acupuncture with PCA reduced the incidence of postoperative PCA-related total complications (odds ratio = 0.44, 95% CI = 0.23 to 0.85, $P=0.01$ ), but may not reduce the incidence of postoperative nausea and vomiting (odds ratio =0.82 , 95% CI =0.49 to 1.36, $P=0.44$ ). Conclusion. This systematic review found that acupuncture with PCA relieved acute pain after back surgery more effectively than PCA alone and could reduce opioid use and the incidence of postoperative PCA-related total complications

Similarities in the Neuropathy Phenotype of Cancer Survivors Who Received Different Classes of Chemotherapy Drugs

With the advent of platinum and taxane compounds used as single agents or in combination regimens, survival rates for some of the most common cancers have improved substantially. However, information on differences in the chemotherapy-induced peripheral neuropathy (CIPN) phenotype among single and combination regimens is limited. Study's purposes were to evaluate for differences in demographic and clinical characteristics; subjective and objective measures of CIPN; as well as the severity of common symptoms and quality of life among survivors who received platinum- (n = 95), taxane- (n = 200), or platinum and taxane-containing (n = 131) regimens. Patients completed self-report questionnaires (ie, duration of CIPN, pain intensity, pain qualities, pain interference) and underwent a physical examination that evaluated light touch, pain, and cold sensations and balance. For most of the subjective and objective measures of CIPN, as well as symptom severity and quality of life scores, no differences were found among the 3 chemotherapy groups. In all 3 chemotherapy treatment groups, CIPN was a painful, small fiber, and length dependent neuropathy. These findings support the hypothesis that CIPN induced by different classes of chemotherapy, as single agents or in combination, produce a similar CIPN phenotype which raises the possibility that CIPN induced by diverse chemotherapy protocols has the same underlying mechanism. PERSPECTIVE: In this study, that compared patients who received only platinum, only taxane, or both platinum and taxane containing regimens, no differences were found among the 3 groups in the CIPN phenotype. Findings raise the possibility that CIPN induced by diverse chemotherapy protocols has the same underlying mechanism.

Characterization of Patients With and Without Painful Peripheral Neuropathy After Receiving Neurotoxic Chemotherapy: Traditional Quantitative Sensory Testing vs C-Fiber and Aδ-Fiber Selective Diode Laser Stimulation

Painful chemotherapy induced peripheral neuropathy (CIPN) is a common complication of chemotherapy with drugs such as taxanes and platinum compounds. Currently, no methods are available for early detection of sensory changes that are associated with painful CIPN, nor are there biomarkers that are specific to painful CIPN. This study aimed to compare Diode Laser fiber type-selective stimulator (DLss), a method to selectively stimulate cutaneous C and Aδ fibers, to traditional quantitative sensory testing (QST) in determining psychophysical differences between patients with painful CIPN and a control group. Sensory testing was performed on the dorsal mid-foot of 20 patients with painful neuropathy after taxane- or platinum-based chemotherapy, and 20 patients who received similar neurotoxic chemotherapy, without painful CIPN. In a multivariable analysis, C-fiber to Aδ fiber detection threshold ratio, measured by DLss, was significantly different between the groups (P <.05). While QST parameters such as warmth detection threshold were different between the groups in univariate analyses, these findings were likely attributable to group differences in patient age and cumulative chemotherapy dose. PERSPECTIVE: In this study, fiber-specific DLss test showed potential in identifying sensory changes that are specific for painful neuropathy, encouraging future testing of this approach as a biomarker for early detection of painful CIPN. TRIAL REGISTRATION: The study was approved by the Washington University Institutional Review Board (#201807162) and registered at ClinicalTrials.gov (NCT03687970).

Adaptation to tonic heat in healthy subjects and patients with sensory polyneuropathy

Adaptation to a constant sensory stimulus involves many sites along the path of sensory volleys towards perception. The evaluation of such phenomenon may be of clinical interest. We studied adaptation to a constant temperature stimulus in healthy subjects to set normative data, and in patients with sensory polyneuropathy (SPN), as proof of concept. Twenty-six healthy subjects and 26 patients with SPN in the context of chemotherapy treatment with oxaliplatin for colon cancer were instructed to express through an electronic VAS system (eVAS) the level of sensation felt when a thermode set at either 39º, 41º, 43º, 45º or 47º was applied to their ventral forearm. The eVAS recordings showed typically an abrupt onset that slowed to approach maximum sensation and continued with a slow decrease indicating adaptation. The time to respond (TR), the velocity of the initial response (VR), the maximum sensation (MA), the time to reach MA (MAt), the onset of adaptation (AO), and the decrease in the sensation level with respect to MA at 30 s after stimulus application (SL30), were dependent on the temperature level in all subjects. However, patients showed significantly delayed TR, slowed VR, decreased MA, delayed AO, and reduced SL30, with respect to healthy subjects. Differences were more pronounced at low temperature levels, with absent AO in 25 patients vs. 2 healthy subjects at temperatures of 39º and 41ºC. The study of adaptation to a constant temperature stimulus can furnish valuable data for the assessment of SPN patients.

Prognostic value of cutaneous reinnervation with GAP-43 in oxaliplatin-induced neuropathy

Background and purpose

Oxaliplatin-induced neuropathy (OIN) implies axonal damage of both small and large sensory nerve fibers. We aimed at comparing the neurophysiological changes occurred after treatment and the capability to recovery based on histological marker of re-innervation GAP-43.

Methods

48 patients with cancer were assessed before and after chemotherapy (at 3 months and 12 months if available). We recorded ulnar and sural sensory nerve action potentials (SNAP), determined quantitative sensory thresholds for warm and cold (WDT, CDT), pain thresholds and collected a distal biopsy of skin to assess the intra-epidermal nerve fiber density (IENFD) with PGP9.5 and GAP-43 markers (in a subgroup of 19 patients).

Results

Increased WDT and CDT as well as diminished IENFD at distal leg were already found in 30% of oncologic patients before treatment. After oxaliplatin, there was a significant increase in thermal thresholds in 52% of patients, and a decrease of SNAP amplitude in the sural nerve in 67% patients. IENFD was reduced in 47% and remained unchanged in 37% after oxiplatin. The density of GAP-43 + fibers and GAP-43/PGP 9.5 ratio was similar before and after treatment showing that cutaneous re-innervation is preserved despite no clinical recovery was observed after one year.

Conclusion

Non-selective axonal loss affects sensory fibers in OIN. However, the presence of intra-epidermal regenerative sprouts detected by GAP-43 may reduce the impact of neurotoxicity in the small fibers with long-term sequelae mostly on myelinated nerve endings. Pre-oxaliplatin GAP-43 failed to identify patients with higher risk of damage or worse recovery after treatment.

Docetaxel Treatment for Metastatic Hormone-sensitive Prostate Cancer in Daily Practice

BACKGROUND

Currently, metastatic hormone-sensitive prostate cancer (mHSPC) patients are often treated with docetaxel chemotherapy at the initiation of hormonal therapy. This treatment is based on the results of two pivotal trials. However, trial populations are not a representative of real-world patient populations.

OBJECTIVE

We aimed to analyze whether survival rates in our daily practice cohort is comparable with those in clinical trials and to characterize the tolerability of docetaxel chemotherapy in daily practice.

DESIGN SETTING AND PARTICIPANTS

In this retrospective cohort analysis, we studied 159 mHSPC patients treated with early docetaxel from April 2014 up to June 2020 in a top clinical hospital in The Netherlands. Patients were selected using hospital pharmacy records.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We compared the results of our cohort with the results of the cohorts of the two pivotal trials. We aimed to analyze the survival rates in our cohort and characterize the tolerability of docetaxel chemotherapy in daily practice.

RESULTS AND LIMITATIONS

Despite the relatively high number of comorbidities in our daily practice cohort, overall survival of our cohort showed great similarity with that of the two pivotal trials: 60.2 mo compared with 57.6 and 59.1 mo. Furthermore, early docetaxel was well tolerated in daily practice. Nearly 90% of the patients completed the full six cycles, and polyneuropathy led to relatively few dose reductions (6.9%).

CONCLUSIONS

Early docetaxel is well tolerated in daily practice. Our daily practice cohort showed great similarity in overall survival to the clinical trials. Our results might be of interest in the developing landscape of mHSPC treatment.

PATIENT SUMMARY

We studied docetaxel chemotherapy for metastatic prostate cancer in daily practice. These patients have the same survival as selected patients participating in clinical trials. Docetaxel was well tolerated in daily practice.

Neurophysiologic assessment of small fibre damage in chemotherapy-induced peripheral neuropathy

OBJECTIVE

In patients with chemotherapy-induced peripheral neuropathy (CIPN), demonstration of small fibre (SF) damage is important to understand chronic late effects.

METHODS

Thirty patients having complaints compatible with possible CIPN following treatment with oxaliplatin or docetaxel were compared with 27 healthy subjects. All subjects were evaluated with quantitative sensory testing (QST) assessing SF function and laser evoked potentials (LEP). In addition, SF-damage was assessed using cutaneous silent periods evoked with electrical (El-CSP) and laser (Ls-CSP) stimuli.

RESULTS

For LEP, N2P2 amplitudes were significantly smaller in patients than controls in both upper (P = 0.007) and lower extremities (P = 0.002), and the N1 amplitude in upper extremities of patients were significantly smaller than in controls (P = 0.001). SF-QST, LEP, Ls-CSP, and El-CSP were abnormal in 10 (33.3%), 16 (53.3%), 19 (63.3%), and 24 (80%) of CIPN patients, respectively.

CONCLUSIONS

In patients with possible CIPN, El-CSP and Ls-CSP were more often abnormal than LEP and QST. This is probably because El-CSP and Ls-CSP inform mainly about peripheral nociceptive fibres, while LEP and QST inform about peripheral and central nociceptive pathways together.

SIGNIFICANCE

LEP and QST are established methods to detect SF-damage. El- and Ls-CSP might help clinicians in diagnosing SF-damage.

Comparison between quantitative and subjective assessments of chemotherapy-induced peripheral neuropathy in cancer patients: A prospective cohort study

OBJECTIVE

Chemotherapy-induced peripheral neuropathy (CIPN) is a common adverse event experienced by cancer patients. In general, CIPN is evaluated subjectively based on patient self-assessment or clinician-reported scales; evidence supporting the utility and validity of quantitative sensory tests (QST) is lacking in this patient population. The aim of this study was to objectively assess CIPN of lower extremities by QSTs, and to evaluate the concordance between QSTs and subjective assessments.

METHODS

In this prospective cohort study, outpatients with cancer receiving chemotherapy were recruited at a single university hospital. We assessed CIPN at the lower extremities at baseline and three months after baseline. The QSTs were performed by applying a monofilament and a tuning fork to determine touch and vibration thresholds, respectively, at the affected site. Subjective assessments were performed based on the visual analog scale (VAS) and the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) toxicity grade. Kappa coefficients were calculated to evaluate the concordance between QSTs and subjective assessments.

RESULTS

After exclusion and drop-outs during follow-up, nineteen patients were included in the analysis. The prevalence of patients with abnormal sensation was 37% based on QSTs, 32% based on the VAS, and 14% based on CTCAE grading, respectively. Kappa coefficients were 0.32 between QSTs and VAS, and 0.28 between QSTs and CTCAE.

CONCLUSIONS

The concordance rates between quantitative and subjective assessments were low. CIPN should be assessed using both quantitative and subjective assessments.

Animal models of pain: Diversity and benefits

Chronic pain is a maladaptive neurological disease that remains a major health problem. A deepening of our knowledge on mechanisms that cause pain is a prerequisite to developing novel treatments. A large variety of animal models of pain has been developed that recapitulate the diverse symptoms of different pain pathologies. These models reproduce different pain phenotypes and remain necessary to examine the multidimensional aspects of pain and understand the cellular and molecular basis underlying pain conditions. In this review, we propose an overview of animal models, from simple organisms to rodents and non-human primates and the specific traits of pain pathologies they model. We present the main behavioral tests for assessing pain and investing the underpinning mechanisms of chronic pathological pain. The validity of animal models is analysed based on their ability to mimic human clinical diseases and to predict treatment outcomes. Refine characterization of pathological phenotypes also requires to consider pain globally using specific procedures dedicated to study emotional comorbidities of pain. We discuss the limitations of pain models when research findings fail to be translated from animal models to human clinics. But we also point to some recent successes in analgesic drug development that highlight strategies for improving the predictive validity of animal models of pain. Finally, we emphasize the importance of using assortments of preclinical pain models to identify pain subtype mechanisms, and to foster the development of better analgesics.

Oxaliplatin- and docetaxel-induced polyneuropathy: clinical and neurophysiological characteristics

The aim of this study was to evaluate the presence and characterization of chemotherapy-induced neuropathy (CIPN) and neuropathic pain 5 years after adjuvant chemotherapy with docetaxel or oxaliplatin. Patients from an ongoing prospective study, who had received adjuvant chemotherapy with docetaxel or oxaliplatin in 2011 to 2012 were invited to participate. The patients underwent a thorough examination with interview, neurological examination, questionnaires, assessment tools, nerve conduction studies (NCS), quantitative sensory testing, MScan motor unit number estimation (MUNE), and corneal confocal microscopy (CCM). Patients were divided into no, possible, probable, and confirmed CIPN. Out of the 132 eligible patients, 63 agreed to participate: 28 had received docetaxel and 35 had received oxaliplatin. Forty-one percent had confirmed CIPN, 34% possible or probable CIPN, and 22% did not have CIPN. The CIPN was characterized mainly by sensory nerve fiber loss, with a more pronounced large fiber than small fiber loss but also some motor fiber loss identified on NCS and MUNE. In general, patients had mild neuropathy with relatively low scores on assessment tools and no association with mood and quality of life. CCM was not useful as a diagnostic tool. Of the patients with probable or confirmed CIPN, 30% experienced pain, which was most often mild, but still interfered moderately with daily life in 20% to 25% and was associated with lower quality of life. In conclusion CIPN was confirmed in 41% 5 years after chemotherapy. The neuropathy was generally mild, but in patients with neuropathic pain it was associated with lower quality of life.

Neuropathic Pain: From Mechanisms to Treatment

Neuropathic pain caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition with major impact on quality of life. Examples include trigeminal neuralgia, painful polyneuropathy, postherpetic neuralgia, and central poststroke pain. Most patients complain of an ongoing or intermittent spontaneous pain of, for example, burning, pricking, squeezing quality, which may be accompanied by evoked pain, particular to light touch and cold. Ectopic activity in, for example, nerve-end neuroma, compressed nerves or nerve roots, dorsal root ganglia, and the thalamus may in different conditions underlie the spontaneous pain. Evoked pain may spread to neighboring areas, and the underlying pathophysiology involves peripheral and central sensitization. Maladaptive structural changes and a number of cell-cell interactions and molecular signaling underlie the sensitization of nociceptive pathways. These include alteration in ion channels, activation of immune cells, glial-derived mediators, and epigenetic regulation. The major classes of therapeutics include drugs acting on α₂δ subunits of calcium channels, sodium channels, and descending modulatory inhibitory pathways.

Chemotherapy-induced peripheral neuropathy: where are we now?

Chemotherapy-induced peripheral neuropathy (CIPN) is a major challenge, with increasing impact as oncological treatments, using potentially neurotoxic chemotherapy, improve cancer cure and survival. Acute CIPN occurs during chemotherapy, sometimes requiring dose reduction or cessation, impacting on survival. Around 30% of patients will still have CIPN a year, or more, after finishing chemotherapy. Accurate assessment is essential to improve knowledge around prevalence and incidence of CIPN. Consensus is needed to standardize assessment and diagnosis, with use of well-validated tools, such as the EORTC-CIPN 20. Detailed phenotyping of the clinical syndrome moves toward a precision medicine approach, to individualize treatment. Understanding significant risk factors and pre-existing vulnerability may be used to improve strategies for CIPN prevention, or to use targeted treatment for established CIPN. No preventive therapies have shown significant clinical efficacy, although there are promising novel agents such as histone deacetylase 6 (HDAC6) inhibitors, currently in early phase clinical trials for cancer treatment. Drug repurposing, eg, metformin, may offer an alternative therapeutic avenue. Established treatment for painful CIPN is limited. Following recommendations for general neuropathic pain is logical, but evidence for agents such as gabapentinoids and amitriptyline is weak. The only agent currently recommended by the American Society of Clinical Oncology is duloxetine. Mechanisms are complex with changes in ion channels (sodium, potassium, and calcium), transient receptor potential channels, mitochondrial dysfunction, and immune cell interactions. Improved understanding is essential to advance CIPN management. On a positive note, there are many potential sites for modulation, with novel analgesic approaches.

Recent advances in understanding chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common cause of pain and poor quality of life for those undergoing treatment for cancer and those surviving cancer. Many advances have been made in the pre-clinical science; despite this, these findings have not been translated into novel preventative measures and treatments for CIPN. This review aims to give an update on the pre-clinical science, preventative measures, assessment and treatment of CIPN.

A Comparative Review of Chemotherapy-Induced Peripheral Neuropathy in In Vivo and In Vitro Models

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse effect caused by several classes of widely used anticancer therapeutics. Chemotherapy-induced peripheral neuropathy frequently leads to dose reduction or discontinuation of chemotherapy regimens, and CIPN symptoms can persist long after completion of chemotherapy and severely diminish the quality of life of patients. Differences in the clinical presentation of CIPN by widely diverse classifications of anticancer agents have spawned multiple mechanistic hypotheses that seek to explain the pathogenesis of CIPN. Despite its clinical relevance, common occurrence, and extensive investigation, the pathophysiology of CIPN remains unclear. Furthermore, there is no unequivocal gold standard for the prevention and treatment of CIPN. Herein, we review in vivo and in vitro models of CIPN with a focus on histopathological changes and morphological features aimed at understanding the pathophysiology of CIPN and identify gaps requiring deeper exploration. An elucidation of the underlying mechanisms of CIPN is imperative to identify potential targets and approaches for prevention and treatment.

Quantification of Small Fiber Neuropathy in Chemotherapy-Treated Patients

Chemotherapy-induced peripheral neuropathy (CIPN) is a major, dose-limiting side effect of treatment with neurotoxic cancer treatments which can result in long-term impairment. Deficits often reflect a large fiber polyneuropathy, however small fiber involvement resulting in neuropathic pain and autonomic dysfunction can occur. Quantification of both CIPN and small fiber neuropathy (SFN) remains a challenge. Accordingly, the prevalence and pathophysiology of small fiber neuropathy amongst cancer survivors remains poorly understood. This review will provide an overview of the clinical features of SFN associated with neurotoxic cancer treatments as well as a summary of current assessment tools for evaluating small fiber function, and their use in patients treated with neurotoxic chemotherapies. The continued development and utilization of novel measures quantifying small fiber involvement will help elucidate the pathophysiology underlying symptoms of CIPN and assist in informing treatment approaches. Accurately identifying subgroups of patients with neuropathic symptoms which may respond to existing pain medication may reduce the impact of CIPN and improve long-term quality of life as well as provide better categorization of patients for future clinical trials of neuroprotective and treatment strategies for CIPN. PERSPECTIVE: This review provides a critical analysis of SFN associated with neurotoxic cancer treatments and the assessment tools for evaluating small fiber dysfunction in cancer patients. Quantification of small fiber involvement in CIPN will assist in identifying subgroups of patients with neuropathic symptoms which may respond to existing pain medications.

Animal models of chemotherapy-induced peripheral neuropathy: A machine-assisted systematic review and meta-analysis

We report a systematic review and meta-analysis of research using animal models of chemotherapy-induced peripheral neuropathy (CIPN). We systematically searched 5 online databases in September 2012 and updated the search in November 2015 using machine learning and text mining to reduce the screening for inclusion workload and improve accuracy. For each comparison, we calculated a standardised mean difference (SMD) effect size, and then combined effects in a random-effects meta-analysis. We assessed the impact of study design factors and reporting of measures to reduce risks of bias. We present power analyses for the most frequently reported behavioural tests; 337 publications were included. Most studies (84%) used male animals only. The most frequently reported outcome measure was evoked limb withdrawal in response to mechanical monofilaments. There was modest reporting of measures to reduce risks of bias. The number of animals required to obtain 80% power with a significance level of 0.05 varied substantially across behavioural tests. In this comprehensive summary of the use of animal models of CIPN, we have identified areas in which the value of preclinical CIPN studies might be increased. Using both sexes of animals in the modelling of CIPN, ensuring that outcome measures align with those most relevant in the clinic, and the animal's pain contextualised ethology will likely improve external validity. Measures to reduce risk of bias should be employed to increase the internal validity of studies. Different outcome measures have different statistical power, and this can refine our approaches in the modelling of CIPN.

Mechanisms, Predictors, and Challenges in Assessing and Managing Painful Chemotherapy-Induced Peripheral Neuropathy

OBJECTIVE

To describe the known predictors and pathophysiological mechanisms of chronic painful chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors and the challenges in assessing and managing it.

DATA SOURCES

PubMed/Medline, CINAHL, Scopus, and PsycINFO.

CONCLUSION

The research on chronic painful CIPN is limited. Additional research is needed to identify the predictors and pathophysiological mechanisms of chronic painful CIPN to inform the development of assessment tools and management options for this painful and possibly debilitating condition.

IMPLICATIONS FOR NURSING PRACTICE

Recognition of the predictors of chronic painful CIPN and proactive CIPN assessment and palliative management are important steps in reducing its impact on physical function and quality of life.

Transition from acute to chronic pain after surgery

Over the past decade there has been an increasing reliance on strong opioids to treat acute and chronic pain, which has been associated with a rising epidemic of prescription opioid misuse, abuse, and overdose-related deaths. Deaths from prescription opioids have more than quadrupled in the USA since 1999, and this pattern is now occurring globally. Inappropriate opioid prescribing after surgery, particularly after discharge, is a major cause of this problem. Chronic postsurgical pain, occurring in approximately 10% of patients who have surgery, typically begins as acute postoperative pain that is difficult to control, but soon transitions into a persistent pain condition with neuropathic features that are unresponsive to opioids. Research into how and why this transition occurs has led to a stronger appreciation of opioid-induced hyperalgesia, use of more effective and safer opioid-sparing analgesic regimens, and non-pharmacological interventions for pain management. This Series provides an overview of the epidemiology and societal effect, basic science, and current recommendations for managing persistent postsurgical pain. We discuss the advances in the prevention of this transitional pain state, with the aim to promote safer analgesic regimens to better manage patients with acute and chronic pain.

Searching for analgesic drug candidates alleviating oxaliplatin-induced cold hypersensitivity in mice

Oxaliplatin is a third-generation, platinum-based derivative used to treat advanced colorectal cancer. Within the patient population on oxaliplatin therapy, a lower incidence of hematological adverse effects and gastrointestinal toxicity is noted, but severe neuropathic pain episodes characterized by increased cold and tactile hypersensitivity are present in ~95% of patients. This drug is also used to induce a rodent model of chemotherapy-induced peripheral neuropathy (CIPN)-related neuropathic pain which is widely used in the search for novel therapies for CIPN prevention and treatment. This paper provides a step-by-step, detailed description of the prevention and intervention protocols used in our laboratory for the assessment of oxaliplatin-induced cold allodynia in mice. To establish cold sensitivity in mice, the cold plate test was used. Latencies to pain reaction in response to cold stimulus (2.5°C) for vehicle-treated non-neuropathic mice, vehicle-treated mice injected with oxaliplatin (neuropathic control), and oxaliplatin-treated mice treated additionally with duloxetine are compared. Duloxetine is a serotonin/noradrenaline reuptake inhibitor which was found to produce significant pain relief in patients with CIPN symptoms. In our present study, duloxetine administered intraperitoneally at the dose of 30 mg/kg served as a model antiallodynic drug which attenuated or partially prevented cold allodynia caused by oxaliplatin.

Contribution of Loss of Large Fiber Function to Pain in 2 Samples of Oncology Patients

OBJECTIVES

Numbness associated with neuropathic pain suggests the loss of function in myelinated, large diameter sensory neurons. The purpose of this study was to examine the relationships between pain severity and subjective (ie, severity of numbness) and objective (ie, loss of light touch sensations, vibration thresholds) measures of loss of large fiber function in adult survivors with chemotherapy-induced peripheral neuropathy (CIPN, n=426) and breast cancer patients with persistent postsurgical pain (n=80).

MATERIAL AND METHODS

For both samples, average pain and numbness were evaluated using a 0 to 10 numeric rating scale. Loss of light touch sensations in the hands and feet of patients with CIPN and in the upper arm of patients at 5 and 6 months following breast cancer surgery were assessed using Semmes Weinstein monofilaments. Loss of vibration in the hands and feet of patients with CIPN was assessed using a biothesiometer. Pearson Product Moment correlation coefficients were calculated between average pain and the number or percentage of sites with loss of light touch sensations, mean vibration thresholds, and the severity of numbness.

RESULTS

For both pain conditions, average pain scores were significantly correlated with objective measures of large fiber function (r=0.12 to 0.34; all P<0.05) and numbness (r=0.22 to 0.52; all P<0.008).

DISCUSSION

Our findings, in 2 independent samples of oncology patients, suggest that loss of function of myelinated, large diameter fibers contributes to the severity of neuropathic pain.

Reduced intraepidermal nerve fibre density, glial activation, and sensory changes in HIV type-1 Tat-expressing female mice: involvement of Tat during early stages of HIV-associated painful sensory neuropathy

INTRODUCTION

HIV infection is associated with chronic pain states, including sensory neuropathy, which affects greater than 40% of patients.

OBJECTIVES AND METHODS

To determine the impact of HIV-Tat induction on nociceptive behaviour in female mice conditionally expressing HIV Tat1-86 protein through a doxycycline (DOX)-driven glial fibrillary acidic protein promoter, intraepidermal nerve fibre density and immune cell activation in the dorsal root ganglion (DRG) and spinal cord were assessed by immunohistochemistry. Mice were assessed for mechanical and thermal sensitivity for 9 weeks using von-Frey and Hargreaves tests.

RESULTS

Intraepidermal nerve fibre density was significantly reduced after 6 weeks of Tat induction, similar to sensory neuropathy seen in clinical HIV infection. Tat induction through DOX caused a significant reduction in paw withdrawal thresholds in a time-dependent manner starting the 4th week after Tat induction. No changes in paw withdrawal latencies were seen in Tat(-) control mice lacking the tat transgene. Although reductions in paw withdrawal thresholds increased throughout the study, no significant change in spontaneous motor activity was observed. Spinal cord (cervical and lumbar), DRG, and hind paw skin were collected at 8 days and 6 weeks after Tat induction. HIV-Tat mRNA expression was significantly increased in lumbar DRG and skin samples 8 days after DOX treatment. Tat induced a significant increase in the number of Iba-1 positive cells at 6 weeks, but not after 8 days, of exposure. No differences in glial fibrillary acidic protein immunoreactivity were observed.

CONCLUSION

These results suggest that Tat protein contributes to painful HIV-related sensory neuropathy during the initial stages of the pathogenesis.