Chemotherapy-induced peripheral neuropathy in the adult

Identifying trajectories and predictors of chemotherapy-induced peripheral neuropathy symptoms, physical functioning, and falls across treatment and recovery in adults treated with neurotoxic chemotherapy: the PATTERN observational study protocol (NCT05790538)

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is a debilitating and dose-limiting side effect of systemic cancer therapy. In many cancer survivors, CIPN persists after treatment ends and is associated with functional impairments, abnormal gait patterns, falls, and diminished quality of life. However, little is known regarding which patients are most likely to develop CIPN symptoms that impair mobility and increase fall risk, when this risk develops, or the optimal timing of early intervention efforts to mitigate the impact of CIPN on functioning and fall risk. This study will address these knowledge gaps by (1) characterizing trajectories of symptoms, functioning, and falls before, during, and after treatment in adults prescribed neurotoxic chemotherapy for cancer; and (2) determining the simplest set of predictors for identifying individuals at risk for CIPN-related functional decline and falls.

METHODS

We will enroll 200 participants into a prospective, observational study before initiating chemotherapy and up to 1 year after completing chemotherapy. Eligible participants are aged 40-85 years, diagnosed with stage I-III cancer, and scheduled to receive neurotoxic chemotherapy. We perform objective assessments of vibratory and touch sensation (biothesiometry, tuning fork, monofilament tests), standing and dynamic balance (quiet stance, Timed-Up-and-Go tests), and upper and lower extremity strength (handgrip dynamometry, 5-time repeated chair stand test) in the clinic at baseline, every 4-6 weeks during chemotherapy, and quarterly for 1 year post-chemotherapy. Participants wear devices that passively and continuously measure daily gait quality and physical activity for 1 week after each objective assessment and self-report symptoms (CIPN, insomnia, fatigue, dizziness, pain, cognition, anxiety, and depressive symptoms) and falls via weekly electronic surveys. We will use structural equation modeling, including growth mixture modeling, to examine patterns in trajectories of changes in symptoms, functioning, and falls associated with neurotoxic chemotherapy and then search for distinct risk profiles for CIPN.

DISCUSSION

Identifying simple, early predictors of functional decline and fall risk in adults with cancer receiving neurotoxic chemotherapy will help identify individuals who would benefit from early and targeted interventions to prevent CIPN-related falls and disability.

TRIAL REGISTRATION

This study was retrospectively registered with ClinicalTrials.gov (NCT05790538) on 3/30/2023.

Spinal cord dorsal horn sensory gate in preclinical models of chemotherapy-induced painful neuropathy and contact dermatitis chronic itch becomes less leaky with Kcc2 gene expression-enhancing treatments

Low intraneuronal chloride in spinal cord dorsal horn (SCDH) pain relay neurons is of critical relevance for physiological transmission of primary sensory afferents because low intraneuronal chloride dictates GABA-ergic and glycin-ergic neurotransmission to be inhibitory. If neuronal chloride rises to unphysiological levels, the primary sensory gate in the spinal cord dorsal horn becomes corrupted, with resulting behavioral hallmarks of hypersensitivity and allodynia, for example in pathological pain. Low chloride in spinal cord dorsal horn neurons relies on the robust gene expression of Kcc2 and sustained transporter function of the KCC2 chloride-extruding electroneutral transporter. Based on a recent report where we characterized the GSK3-inhibitory small molecule, kenpaullone, as a Kcc2 gene expression-enhancer that potently repaired diminished Kcc2 expression and KCC2 transporter function in SCDH pain relay neurons, we extend our recent findings by reporting (i) effective pain control in a preclinical model of taxol-induced painful peripheral neuropathy that was accomplished by topical application of a TRPV4/TRPA1 dual-inhibitory compound (compound 16-8), and was associated with the repair of diminished Kcc2 gene expression in the SCDH; and (ii) potent functioning of kenpaullone as an antipruritic in a DNFB contact dermatitis preclinical model. These observations suggest that effective peripheral treatment of chemotherapy-induced painful peripheral neuropathy impacts the pain-transmitting neural circuit in the SCDH in a beneficial manner by enhancing Kcc2 gene expression, and that chronic pruritus might be relayed in the primary sensory gate of the spinal cord, following similar principles as pathological pain, specifically relating to the critical functioning of Kcc2 gene expression and the KCC2 transporter function.

Integrated Medicine for Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of typical chemotherapeutics among cancer survivors. Despite the recent progress, the effective prevention and treatment strategies for CIPN remain limited. Better understanding of the pathogenesis of CIPN may provide new niches for developing a new ideal therapeutic strategy. This review summarizes the current understanding of CIPN and current recommendations along with completed/active clinical trials and aims to foster translational research to improve the development of effective strategies for managing CIPN.

A Randomized Controlled Trial to Assess the Effectiveness of Muscle Strengthening and Balancing Exercises on Chemotherapy-Induced Peripheral Neuropathic Pain and Quality of Life Among Cancer Patients

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) is the presence of tingling, burning, itching, and unpleasant sensations in hands and feet due to nerve damage by chemotherapy. Exercise rehabilitation has potential to prevent or alleviate CIPN.

OBJECTIVE

The aim of this study was to assess the effectiveness of muscle strengthening and balancing exercises on CIPN pain and quality of life (QOL) among cancer patients.

METHODS

The randomized controlled trial included 45 cancer patients from a tertiary care hospital in India receiving chemotherapeutic drugs paclitaxel and carboplatin and found to have CIPN. Subjects were randomly allocated to exercise (n1 = 22) and usual care (n2 = 23) groups. The exercise group received home-based muscle strengthening and balancing exercise for 10 weeks. Data regarding demographic, clinical characteristics, CIPN, neuropathic pain, and QOL were collected by structured questionnaires Chemotherapy-Induced Peripheral Neuropathy Assessment Tool, nerve conduction velocity, Leeds Assessment of Neuropathic Symptoms and Signs pain scale, and European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire.

RESULTS

The 2 groups were homogenous regarding demographic variables. In clinical characteristics, the exercise group had larger body surface area and received a higher dose of paclitaxel. Significant reduction in neuropathic pain scores (P < .0001) and improvement in Functional QOL (P = .0002), Symptom QOL (P = .0003), Global Health Status QOL (P = .004) scores were observed after intervention in the exercise group than the usual-care group.

CONCLUSION

Muscle strengthening and balancing exercises are effective in reducing CIPN pain and improving QOL among cancer patients.

IMPLICATIONS FOR PRACTICE

Muscle strengthening and balancing exercises can be used as a complementary therapy for effective management of CIPN.

Current View of Diagnosing Small Fiber Neuropathy

Small fiber neuropathy (SFN) is a disorder of the small myelinated Aδ-fibers and unmyelinated C-fibers [5, 6]. SFN might affect small sensory fibers, autonomic fibers or both, resulting in sensory changes, autonomic dysfunction or combined symptoms [7]. As a consequence, the symptoms are potentially numerous and have a large impact on quality of life [8]. Since diagnostic methods for SFN are numerous and its pathophysiology complex, this extensive review focusses on categorizing all aspects of SFN as disease and its diagnosis. In this review, sensitivity in combination with specificity of different diagnostic methods are described using the areas under the curve. In the end, a diagnostic work-flow is suggested based on different phenotypes of SFN.

Neurotoxicity of antineoplastic drugs: Mechanisms, susceptibility, and neuroprotective strategies

This review summarizes the adverse effects on the central and/or peripheral nervous systems that may occur in response to antineoplastic drugs. In particular, we describe the neurotoxic side effects of the most commonly used drugs, such as platinum compounds, doxorubicin, ifosfamide, 5-fluorouracil, vinca alkaloids, taxanes, methotrexate, bortezomib and thalidomide. Neurotoxicity may result from direct action of compounds on the nervous system or from metabolic alterations produced indirectly by these drugs, and either the central nervous system or the peripheral nervous system, or both, may be affected. The incidence and severity of neurotoxicity are principally related to the dose, to the duration of treatment, and to the dose intensity, though other factors, such as age, concurrent pathologies, and genetic predisposition may enhance the occurrence of side effects. To avoid or reduce the onset and severity of these neurotoxic effects, the use of neuroprotective compounds and/or strategies may be helpful, thereby enhancing the therapeutic effectiveness of antineoplastic drug.

Comparison of forward and backward gait characteristics between those with and without a history of breast cancer

BACKGROUND

Decreased muscular strength and poorer postural stability impact the physical function of breast cancer survivors (BCS) and increases their risk of falls. Gait assessment, particularly in the backward direction, is often used as an indicator of fall risk in several populations. However this information is unknown in BCS.

RESEARCH QUESTION

What are the differences in forward, backward, and accelerated forward walking in BCS in comparison to individuals without a prior cancer diagnosis?

METHODS

17 postmenopausal BCS (mean age: 58.5 (8.5) years) and 17 age-matched women without a prior cancer diagnosis (mean age: 59.11 (5.55) years) completed 5 trials each of forward, backward, and fast forward walking conditions. Absolute (Means) and variability (Coefficient of variation) estimates were obtained for spatio-temporal gait parameters. Lower body, upper body and handgrip strengths were measured.

RESULTS

For absolute estimates of gait, significant group main effects indicated that BCS had 7% shorter step length (P = 0.019) and 8% slower gait speed (P = 0.048). For variability estimates of gait, there was a significant interaction for stance time (P = 0.035). BCS had greater stance time variability during forward and fast forward conditions, but lesser variability during backward condition. Averaged across all the conditions, BCS had 38% greater step length variability (P = 0.043), 50% greater gait speed variability (P = 0.028), and 28.5% greater single support time variability (P = 0.004). Averaged across both the groups, all the variables except for swing time variability were significantly different among the conditions (all P< = 0.013). BCS also had significantly reduced upper body strength (P = 0.036).

SIGNIFICANCE

Slower and shorter steps while walking both forwards and backwards could be indicative of a more cautious gait strategy by BCS. Also, BCS possibly focused on controlling spatial parameters during forward walking but temporal parameters while backward walking. Whether these alterations are related to an increased fall risk within BCS needs to be determined.

Falls, Functioning, and Disability Among Women With Persistent Symptoms of Chemotherapy-Induced Peripheral Neuropathy

Purpose Chemotherapy-induced peripheral neuropathy (CIPN) may persist after treatment ends and may lead to functional decline and falls. This study compared objective and self-report measures of physical function, gait patterns, and falls between women cancer survivors with and without symptoms of CIPN to identify targets for functional rehabilitation. Methods A secondary data analysis of 512 women cancer survivors (age, 62 ± 6 years; time since diagnosis, 5.8 ± 4.1 years) categorized and compared women self-reporting symptoms of CIPN (CIPN+) with asymptomatic women (CIPN-) on the following: maximal leg strength, timed chair stand, physical function battery, gait characteristics (speed; step number, rate, and length; base of support), self-report physical function and disability, and falls in the past year. Results After an average of 6 years after treatment, 47% of women still reported symptoms of CIPN. CIPN+ had significantly worse self-report and objectively measured function than did CIPN-, with the exception of maximal leg strength and base of support during a usual walk. Gait was slower among CIPN+, with those women taking significantly more, but slower and shorter, steps than did CIPN- (all P < .05). CIPN+ reported significantly more disability and 1.8 times the risk of falls compared with CIPN- ( P < .0001). Increasing symptom severity was linearly associated with worsening function, increasing disability, and higher fall risk (all P < .05). Conclusion This work makes a significant contribution toward understanding the functional impact of CIPN symptoms on cancer survivors. Remarkably, 47% of women in our sample had CIPN symptoms many years after treatment, together with worse function, greater disability, and more falls. CIPN must be assessed earlier in the clinical pathway, and strategies to limit symptom progression and to improve function must be included in clinical and survivorship care plans.

Mutations in the Heme Exporter FLVCR1 Cause Sensory Neurodegeneration with Loss of Pain Perception

Pain is necessary to alert us to actual or potential tissue damage. Specialized nerve cells in the body periphery, so called nociceptors, are fundamental to mediate pain perception and humans without pain perception are at permanent risk for injuries, burns and mutilations. Pain insensitivity can be caused by sensory neurodegeneration which is a hallmark of hereditary sensory and autonomic neuropathies (HSANs). Although mutations in several genes were previously associated with sensory neurodegeneration, the etiology of many cases remains unknown. Using next generation sequencing in patients with congenital loss of pain perception, we here identify bi-allelic mutations in the FLVCR1 (Feline Leukemia Virus subgroup C Receptor 1) gene, which encodes a broadly expressed heme exporter. Different FLVCR1 isoforms control the size of the cytosolic heme pool required to sustain metabolic activity of different cell types. Mutations in FLVCR1 have previously been linked to vision impairment and posterior column ataxia in humans, but not to HSAN. Using fibroblasts and lymphoblastoid cell lines from patients with sensory neurodegeneration, we here show that the FLVCR1-mutations reduce heme export activity, enhance oxidative stress and increase sensitivity to programmed cell death. Our data link heme metabolism to sensory neuron maintenance and suggest that intracellular heme overload causes early-onset degeneration of pain-sensing neurons in humans.

Hereditary Sensory and Autonomic Neuropathy (HSAN) is a genetic disorder mainly characterized by the impairment of sensory neurons, which transmit information about sensations such as pain, temperature and touch. Therefore, unintentional self-injury, leading to ulcers and eventually amputations are common in affected individuals. Although mutations in several genes were previously associated with sensory neurodegeneration and pain insensitivity, the etiology of many cases remains unknown. We here identify mutations in the heme exporter protein FLVCR1 in patients with congenital inability to experience pain. We showed that FLVCR1 mutations results in reduced heme export activity, enhanced oxidative stress and increased sensitivity to programmed cell death. These data assign a surprising role for heme to sensory neuron maintenance.

Quick, non-invasive and quantitative assessment of small fiber neuropathy in patients receiving chemotherapy

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a common, potentially severe and dose-limiting adverse effect; however, it is poorly investigated at an early stage due to the lack of a simple assessment tool. As sweat glands are innervated by small autonomic C-fibers, sudomotor function testing has been suggested for early screening of peripheral neuropathy. This study aimed to evaluate Sudoscan, a non-invasive and quantitative method to assess sudomotor function, in the detection and follow-up of CIPN. Eighty-eight patients receiving at least two infusions of Oxaliplatin only (45.4%), Paclitaxel only (14.8%), another drug only (28.4%) or two drugs (11.4%) were enrolled in the study. At each chemotherapy infusion the accumulated dose of chemotherapy was calculated and the Total Neuropathy Score clinical version (TNSc) was carried out. Small fiber neuropathy was assessed using Sudoscan (a 3-min test). The device measures the Electrochemical Skin Conductance (ESC) of the hands and feet expressed in microSiemens (µS). For patients receiving Oxaliplatin mean hands ESC changed from 73 ± 2 to 63 ± 2 and feet ESC from 77 ± 2 to 66 ± 3 µS (p < 0.001) while TNSc changed from 2.9 ± 0.5 to 4.3 ± 0.4. Similar results were observed in patients receiving Paclitaxel or another neurotoxic chemotherapy. During the follow-up, ESC values of both hands and feet with a corresponding TNSc < 2 were 70 ± 2 and 73 ± 2 µS respectively while they were 59 ± 1.4 and 64 ± 1.5 µS with a corresponding TNSc ≥ 6 (p < 0.0001 and p = 0.0003 respectively). This preliminary study suggests that small fiber neuropathy could be screened and followed using Sudoscan in patients receiving chemotherapy.

Iatrogenic lesions of peripheral nerves

Iatrogenic nerve lesions (INLs) are an integral part of peripheral neurology and require dedicated neurologists to manage them. INLs of peripheral nerves are most frequently caused by surgery, immobilization, injections, radiation, or drugs. Early recognition and diagnosis is important not to delay appropriate therapeutic measures and to improve the outcome. Treatment can be causative or symptomatic, conservative, or surgical. Rehabilitative measures play a key role in the conservative treatment, but the point at which an INL requires surgical intervention should not be missed or delayed. This is why INLs require close multiprofessional monitoring and continuous re-evaluation of the therapeutic effect. With increasing number of surgical interventions and increasing number of drugs applied, it is quite likely that the prevalence of INLs will further increase. To provide an optimal management, more studies about the frequency of the various INLs and studies evaluating therapies need to be conducted. Management of INLs can be particularly improved if those confronted with INLs get state-of-the-art education and advanced training about INLs. Management and outcome of INLs can be further improved if the multiprofessional interplay is optimized and adapted to the needs of the patient, the healthcare system, and those responsible for sustaining medical infrastructure.