Circadian variation of breakthrough pain in cancer patients

Breakthrough pain and rapid-onset opioids in patients with cancer pain: a narrative review

Breakthrough pain is transitory pain that occurs despite the use of opioids for background pain control. Breakthrough pain occurs in 40% to 80% of patients with cancer pain. Despite effective analgesic therapy, patients and their caregivers often feel that their pain is not sufficiently controlled. Therefore, an improved understanding of breakthrough pain and its management is essential for all physicians caring for patients with cancer. This article reviews the definition, clinical manifestations, accurate diagnostic strategies, and optimal treatment options for breakthrough pain in patients with cancer. This review focuses on the efficacy and safety of rapid-onset opioids, which are the primary rescue drugs for breakthrough pain.

Short-term plasticity in the spinal nociceptive system

ABSTRACT

Somatosensory information is delivered to neuronal networks of the dorsal horn (DH) of the spinal cord by the axons of primary afferent neurons that encode the intensity of peripheral sensory stimuli under the form of a code based on the frequency of action potential firing. The efficient processing of these messages within the DH involves frequency-tuned synapses, a phenomenon linked to their ability to display activity-dependent forms of short-term plasticity (STP). By affecting differently excitatory and inhibitory synaptic transmissions, these STP properties allow a powerful gain control in DH neuronal networks that may be critical for the integration of nociceptive messages before they are forwarded to the brain, where they may be ultimately interpreted as pain. Moreover, these STPs can be finely modulated by endogenous signaling molecules, such as neurosteroids, adenosine, or GABA. The STP properties of DH inhibitory synapses might also, at least in part, participate in the pain-relieving effect of nonpharmacological analgesic procedures, such as transcutaneous electrical nerve stimulation, electroacupuncture, or spinal cord stimulation. The properties of target-specific STP at inhibitory DH synapses and their possible contribution to electrical stimulation-induced reduction of hyperalgesic and allodynic states in chronic pain will be reviewed and discussed.

Inhibition of Tumor-Derived C-C Motif Chemokine Ligand 2 Expression Attenuates Tactile Allodynia in NCTC 2472 Fibrosarcoma-Inoculated Mice

Neuropathic pain associated with cancers is caused by tumor growth compressing and damaging nerves, which would also be enhanced by inflammatory factors through sensitizing nociceptor neurons. A troublesome hallmark symptom of neuropathic pain is hypersensitivity to innocuous stimuli, a condition known as "tactile allodynia", which is often refractory to NSAIDs and opioids. The involvement of chemokine CCL2 (monocyte chemoattractant protein-1) in cancer-evoked neuropathic pain is well established, but opinions remain divided as to whether CCL2 is involved in the production of tactile allodynia with tumor growth. In this study, we constructed Ccl2 knockout NCTC 2472 (Ccl2-KO NCTC) fibrosarcoma cells and conducted pain behavioral test using Ccl2-KO NCTC-implanted mice. Implantation of naïve NCTC cells around the sciatic nerves of mice produced tactile allodynia in the inoculated paw. Although the growth of Ccl2 KO NCTC-formed tumors was comparable to that of naïve NCTC-formed tumors, Ccl2-KO NCTC-bearing mice failed to show tactile pain hypersensitivity, suggesting the involvement of CCL2 in cancer-induced allodynia. Subcutaneous administration of controlled-release nanoparticles containing the CCL2 expression inhibitor NS-3-008 (1-benzyl-3-hexylguanidine) significantly attenuated tactile allodynia in naïve NCTC-bearing mice accompanied by a reduction of CCL2 content in tumor masses. Our present findings suggest that inhibition of CCL2 expression in cancer cells is a useful strategy to attenuate tactile allodynia induced by tumor growth. Development of a controlled-release system of CCL2 expression inhibitor may be a preventative option for the treatment of cancer-evoked neuropathic pain. SIGNIFICANCE STATEMENT: The blockade of chemokine/receptor signaling, particularly for C-C motif chemokine ligand 2 (CCL2) and its high-affinity receptor C-C chemokine receptor type 2 (CCR2), has been implicated to attenuate cancer-induced inflammatory and nociceptive pain. This study demonstrated that continuous inhibition of CCL2 production from cancer cells also prevents the development of tactile allodynia associated with tumor growth. Development of a controlled-release system of CCL2 expression inhibitor may be a preventative option for management of cancer-evoked tactile allodynia.

Circadian pain patterns in human pain conditions - A systematic review

BACKGROUND

Chronobiology is the science of how physiological processes in the body follow a pattern of time. Pain has been shown to follow a circadian rhythm, with different types of pain having variable expression along this rhythm.

OBJECTIVE

This article reviews the nature of diurnal variations in pain along with a discussion of the mechanisms of circadian rhythm of pain.

EVIDENCE REVIEW

We conducted a literature search on the PubMed and Google Scholar electronic databases, through April 2022. Publications were screened for English language, full-text availability, and human subjects. Randomized controlled trials and observational trials were included. Data were extracted from studies on patients with acute or chronic pain phenotypes, which provide pain severity data and corresponding diurnal time points.

FINDINGS

The literature search led to the inclusion of 39 studies. A circadian pattern of pain was found to be present in nociceptive, neuropathic, central, and mixed pain states. Postoperative pain, fibromyalgia, trigeminal neuralgia, and migraines were associated with higher pain scores in the morning. Temporomandibular joint pain, neuropathic pain, labor pain, biliary colic, and cluster headaches increased throughout the day to reach a peak in the evening or night. Arthritis and cancer pain were not associated with any circadian rhythmicity. Furthermore, the circadian rhythm of pain was not found to be altered in patients on analgesics.

CONCLUSION

The results of this review suggest that an understanding of diurnal variation may help improve therapeutic strategies in pain management, for instance through analgesic titration.

Basis for diurnal exacerbation of neuropathic pain hypersensitivity and its application for drug development

In addition to diurnal rhythms in physiology and behavior, a variety of pathological conditions also exhibit marked day-night changes in symptom intensity, exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and chronic pain disorders. Currently, novel therapeutic approaches are facilitated by the development of chemical compounds targeted to key proteins that cause diurnal exacerbation of pathological events. Neuropathic pain is a chronic condition that occurs by tumor-induced nerve compression, cancer cell infiltration into the nerve, diabetes, and herpes virus infection. One troublesome hallmark symptom of neuropathic pain is hypersensitivity to normally innocuous stimuli known as "mechanical allodynia" that is often refractory to common analgesic therapies. Millions of patients worldwide presently endure neuropathic pain. We summarize the recent insights gained into the mechanism of diurnal exacerbation of neuropathic pain hypersensitivity and introduce the strategy of circadian clock-based drug development.

Chrono-Pharmaceutical Approaches to Optimize Dosing Regimens Based on the Circadian Clock Machinery

Daily rhythmic variations in biological functions affect the efficacy and/or toxicity of drugs: a large number of drugs cannot be expected to exhibit the same potency at different administration times. The "circadian clock" is an endogenous timing system that broadly regulates metabolism, physiology and behavior. In mammals, this clock governs the oscillatory expression of the majority of genes with a period length of approximately 24 h. Genetic studies have revealed that molecular components of the circadian clock regulate the expression of genes responsible for the sensitivity to drugs and their disposition. The circadian control of pharmacodynamics and pharmacokinetics enables 'chrono-pharmaceutical' applications, namely drug administration at appropriate times of day to optimize the therapeutic index (efficacy vs. toxicity). On the other hand, a variety of pathological conditions also exhibit marked day-night changes in symptom intensity. Currently, novel therapeutic approaches are facilitated by the development of chemical compound targeted to key proteins that cause circadian exacerbation of disease events. This review presents an overview of the current understanding of the role of the circadian biological clock in regulating drug efficacy and disease conditions, and also describes the importance of identifying the difference in the circadian machinery between diurnal and nocturnal animals to select the most appropriate times of day to administer drugs in humans.

Circadian rhythms and pain

The goal of this review is to provide a perspective on the nature and importance of the relationship between the circadian and pain systems. We provide: 1) An overview of the circadian and pain systems, 2) a review of direct and correlative evidence that demonstrates diurnal and circadian rhythms within the pain system; 3) a perspective highlighting the need to consider the role of a proposed feedback loop of circadian rhythm disruption and maladaptive pain; 4) a perspective on the nature of the relationship between circadian rhythms and pain. In summary, we propose that there is no single locus responsible for producing the circadian rhythms of the pain system. Instead, circadian rhythms of pain are a complex result of the distributed rhythms present throughout the pain system, especially those of the descending pain modulatory system, and the rhythms of the systems with which it interacts, including the opioid, endocrine, and immune systems.

Systems and Circuits Linking Chronic Pain and Circadian Rhythms

Research over the last 20 years regarding the link between circadian rhythms and chronic pain pathology has suggested interconnected mechanisms that are not fully understood. Strong evidence for a bidirectional relationship between circadian function and pain has been revealed through inflammatory and immune studies as well as neuropathic ones. However, one limitation of many of these studies is a focus on only a few molecules or cell types, often within only one region of the brain or spinal cord, rather than systems-level interactions. To address this, our review will examine the circadian system as a whole, from the intracellular genetic machinery that controls its timing mechanism to its input and output circuits, and how chronic pain, whether inflammatory or neuropathic, may mediate or be driven by changes in these processes. We will investigate how rhythms of circadian clock gene expression and behavior, immune cells, cytokines, chemokines, intracellular signaling, and glial cells affect and are affected by chronic pain in animal models and human pathologies. We will also discuss key areas in both circadian rhythms and chronic pain that are sexually dimorphic. Understanding the overlapping mechanisms and complex interplay between pain and circadian mediators, the various nuclei they affect, and how they differ between sexes, will be crucial to move forward in developing treatments for chronic pain and for determining how and when they will achieve their maximum efficacy.

Emerging Role of Serum Glucocorticoid-Regulated Kinase 1 in Pathological Pain

Currently, the management of acute and chronic pain in clinical practice remains unsatisfactory due to the existence of limited effective treatments, and novel therapeutic strategies for pathological pain are urgently needed. In the past few decades, the role of serum and glucocorticoid-inducible kinase 1 (SGK1) in the development of pain and diurnal rhythms has been implicated in numerous studies. The expression levels of SGK1 mRNA and protein were found to be elevated in the spinal cord and brain in various pathological pain models. Blocking SGK1 significantly attenuated pain-like responses and the development of pathological pain. These studies provide strong evidence that SGK1 plays a role in the development of various types of pathological pain and that targeting SGK1 may be a novel therapeutic strategy for pain management. In this review article, we provide evidence from animal models for the potential role of SGK1 in the regulation of pathological pain caused by inflammation, nerve injury, psychiatric disorders, and chronic opioid exposure.

The Circadian Rhythm of Breakthrough Pain Episodes in Terminally-ill Cancer Patients

Opioid therapy must be adjusted to the rhythm of a cancer patient’s pain to ensure adequate symptom control at the end of life (EOL). However, to-date no study has explored the rhythm of breakthrough pain (BTP) episodes in terminally-ill cancer patients. This prospective longitudinal study was aimed at verifying the existence of a circadian rhythm of BTP episodes in terminally-ill cancer patients. Consecutive adult cancer patients at their EOL treated with long-acting major opioids to control background pain (Numeric Rating Scale ≤ 3/10) were recruited from two Italian palliative care services. Using a personal diary, patients recorded the frequency and onset of BTP episodes and the analgesic rescue therapy taken for each episode over a 7-day period. Rhythms identified in BTP episodes were validated by Cosinor analysis. Overall, 101 patients were enrolled; nine died during the study period. A total of 665 BTP episodes were recorded (average of 7.2 episodes, mean square error 0.8) per patient, with 80.6% of episodes recorded between 8:00 a.m. and 12:00 a.m. At Cosinor analysis, a circadian rhythm of BTP episodes was observed, with a Midline Estimating Statistics of the Rhythm (MESOR) of 1.5, a double amplitude of 1.8, and an acrophase at 12:30 p.m. (p < 0.001). Oral morphine was the most frequent analgesic rescue therapy employed. In terminally-ill cancer patients, BTP episodes follow a circadian rhythm; thus, tailoring the timing of opioid administration to this rhythm may prevent such episodes. This circadian rhythm of BTP episodes in terminally-ill cancer patients should be confirmed in larger samples.

Accumulation of sorbitol in the sciatic nerve modulates circadian properties of diabetes-induced neuropathic pain hypersensitivity in a diabetic mouse model

The intensity of pain in diabetic neuropathy varies in a circadian time-dependent manner. It is well known that diabetes has two distinct types, which are differentiated based on the cause of the disease. Previous studies have yet to compare the circadian properties of the pain intensity of diabetic neuropathy between type I and type II diabetes. In this study, we demonstrated that the pain intensity of diabetic peripheral neuropathy in a db/db mouse model of type II diabetes showed a significant diurnal oscillation, but such time-dependent oscillation was not detected in a streptozotocin (STZ)-induced type I diabetic mouse model. The polyol pathway-induced accumulation of sorbitol in peripheral nerve cells suppresses Na⁺/K⁺-ATPase activity, which is associated with the intensity of pain in diabetic neuropathy. In db/db mice, this accumulation of sorbitol in peripheral nerve cells showed significant diurnal oscillation. In addition, pain intensity and Na⁺/K⁺-ATPase activity were decreased at the peak time of sorbitol accumulation in these mice. Although STZ-induced diabetic mice also showed sorbitol accumulation and Na⁺/K⁺-ATPase dysfunction, these measures did not oscillate in a time-dependent manner. These findings reveal differences in the circadian properties of pain hypersensitivity in mouse models of type I and type II diabetes, and also provide ideas for developing novel approaches to the management of diabetic neuropathy.

[Breakthrough cancer pain in the elderly]

Breakthrough pain is defined as an acute exacerbation of pain with rapid onset, short duration and moderate or high intensity, which occurs spontaneously or in connection with a predictable or unpredictable event despite there being stabilised and controlled baseline pain. However, there are doubts about the definition, terminology, epidemiology, and assessment of breakthrough pain, with no clear answers or consensus, especially in the elderly population. This non-systematic review summarises the most important aspects of breakthrough pain in the elderly, based on the limited publications there are in that population group.

Changes in ischemic stroke occurrence following daylight saving time transitions

BACKGROUND

Circadian rhythm disruption has been associated with increased risk of ischemic stroke (IS). Daylight saving time (DST) transitions disrupt circadian rhythms and shifts the pattern of diurnal variation in stroke onset, but effects on the incidence of IS are unknown.

METHODS

Effects of 2004-2013 DST transitions on IS hospitalizations and in-hospital mortality were studied nationwide in Finland. Hospitalizations during the week following DST transition (study group, n = 3033) were compared to expected hospitalizations (control group, n = 11,801), calculated as the mean occurrence during two weeks prior to and two weeks after the index week.

RESULTS

Hospitalizations for IS increased during the first two days (Relative Risk 1.08; CI 1.01-1.15, P = 0.020) after transition, but difference was diluted when observing the whole week (RR 1.03; 0.99-1.06; P = 0.069). Weekday-specific increase was observed on the second day (Monday; RR 1.09; CI 1.00-1.90; P = 0.023) and fifth day (Thursday; RR 1.11; CI 1.01-1.21; P = 0.016) after transition. Women were more susceptible than men to temporal changes during the week after DST transitions. Advanced age (>65 years) (RR 1.20; CI 1.04-1.38; P = 0.020) was associated with increased risk during the first two days, and malignancy (RR 1.25; CI 1.00-1.56; P = 0.047) during the week after DST transition.

CONCLUSIONS

DST transitions appear to be associated with an increase in IS hospitalizations during the first two days after transitions but not during the entire following week. Susceptibility to effects of DST transitions on occurrence of ischemic stroke may be modulated by gender, age and malignant comorbidities.

Glucocorticoid regulation of ATP release from spinal astrocytes underlies diurnal exacerbation of neuropathic mechanical allodynia

Diurnal variations in pain hypersensitivity are common in chronic pain disorders, but the underlying mechanisms are enigmatic. Here, we report that mechanical pain hypersensitivity in sciatic nerve-injured mice shows pronounced diurnal alterations, which critically depend on diurnal variations in glucocorticoids from the adrenal glands. Diurnal enhancement of pain hypersensitivity is mediated by glucocorticoid-induced enhancement of the extracellular release of ATP in the spinal cord, which stimulates purinergic receptors on microglia in the dorsal horn. We identify serum- and glucocorticoid-inducible kinase-1 (SGK-1) as the key molecule responsible for the glucocorticoid-enhanced release of ATP from astrocytes. SGK-1 protein levels in spinal astrocytes are increased in response to glucocorticoid stimuli and enhanced ATP release by opening the pannexin-1 hemichannels. Our findings reveal an unappreciated circadian machinery affecting pain hypersensitivity caused by peripheral nerve injury, thus opening up novel approaches to the management of chronic pain.

Neuropathic pain hypersensitivity is known to undergo diurnal variations, although the underlying mechanisms are not clear. Using a sciatic nerve-injury mouse model, the authors find such diurnal changes are mediated by glucocorticoid induced enhancement of ATP release from astrocytes via pannexin-1 hemichannels.

A Systematic Review of the Use of the Palliative Care Outcome Scale and the Support Team Assessment Schedule in Palliative Care

CONTEXT

The Palliative care Outcome Scale (POS) and the Support Team Assessment Schedule (STAS) are two outcome measures used in palliative care settings to assess palliative concerns, needs, and quality of care.

OBJECTIVES

This systematic review builds on the findings of a previous review to appraise the use of the POS and STAS since 2010, particularly the context and nature of their use.

METHODS

MEDLINE, Embase, PsycINFO, British Nursing Index, and CINAHL were searched for studies published between February 2010 and June 2014. Relevant authors were contacted, and reference lists of included studies were searched. Studies reporting validation or the use of the POS or STAS were included, and data on sample population, how the outcome measure was being used, study design, study aim, and results of the study were extracted.

RESULTS

Forty-three studies were included (POS n = 35, STAS n = 8). There was an increase in the use of the POS and STAS in Europe and Africa with the publication of 13 new translations of the POS. Most studies focused on the use, rather than further validation, of the POS and STAS. There has been increasing use of these measures within non-cancer patient groups.

CONCLUSION

The POS and STAS are now used in a wide variety of settings and countries. These tools may be used in the future to compare palliative care needs and quality of care across diverse contexts and patient groups.

Pain in the cancer patient: different pain characteristics CHANGE pharmacological treatment requirements

Twenty years ago, the main barriers to successful cancer pain management were poor assessment by physicians, and patients' reluctance to report pain and take opioids. Those barriers are almost exactly the same today. Cancer pain remains under-treated; in Europe, almost three-quarters of cancer patients experience pain, and almost a quarter of those with moderate to severe pain do not receive any analgesic medication. Yet it has been suggested that pain management could be improved simply by ensuring that every consultation includes the patient's rating of pain, that the physician pays attention to this rating, and a plan is agreed to increase analgesia when it is inadequate. After outlining current concepts of carcinogenesis in some detail, this paper describes different methods of classifying and diagnosing cancer pain and the extent of current under-treatment. Key points are made regarding cancer pain management. Firstly, the pain may be caused by multiple different mechanisms and therapy should reflect those underlying mechanisms - rather than being simply based on pain intensity as recommended by the WHO three-step ladder. Secondly, a multidisciplinary approach is required which combines both pharmacological and non-pharmacological treatment, such as psychotherapy, exercise therapy and electrostimulation. The choice of analgesic agent and its route of administration are considered, along with various interventional procedures and the requirements of palliative care. Special attention is paid to the treatment of breakthrough pain (particularly with fast-acting fentanyl formulations, which have pharmacokinetic profiles that closely match those of breakthrough pain episodes) and chemotherapy-induced neuropathic pain, which affects around one third of patients who receive chemotherapy. Finally, the point is made that medical education should place a greater emphasis on pain therapy, both at undergraduate and postgraduate level.

Correlation between rest-activity rhythm and survival in cancer patients experiencing pain

The purpose of this study was to investigate the influence of rest-activity rhythm on the survival of cancer patients. This study collected data related to cancer patients experiencing pain who had been hospitalized for treatment between August 2006 and October 2007. Data included the Karnofsky Performance Status Index as a representation of functional condition as well as the Brief Pain Inventory and the Pittsburgh Sleep Quality Index. Actigraphic methods were used to record the dichotomy index (I < O) of patients' rest-activity rhythms over periods of three consecutive days. Patients were closely followed until 31 July 2013. Results were analyzed using Kaplan-Meier survival analysis, log-rank testing and Cox proportional hazards regression analysis to evaluate whether alterations in the rest-activity rhythm affected the survival rate of the patients. Of the 68 hospitalized cancer patients experiencing pain at the time of admission, 51 subsequently died within the study period. A significant difference was observed in the survival curves between the regular I < O group and the disrupted I < O group (log rank = 7.942, p = 0.005). A multivariable proportional hazard model was used for analysis of overall survival, revealing that the risk of death within the study period among patients with disrupted I < O was 4.59 times higher than that of patients with regular I < O (95% CI: 1.92-10.96, p = 0.001). Among patients with poor performance status, the risk of death among patients with disrupted I < O was 8.68 times higher than that of patients with regular I < O (95% CI: 2.50-30.09, p = 0.001). Disruptions in rest-activity rhythm were negatively correlated with the survival of hospitalized cancer patients experiencing pain. Effects were particularly pronounced in cancer patients with poor performance status.