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

Circadian functional changes of pain-processing brainstem nuclei and implications for cluster headache: A 7 Tesla imaging study

BACKGROUND

Pain thresholds and primary headaches, including cluster headache attacks, have circadian rhythmicity. Thus, they might share a common neuronal mechanism.

OBJECTIVE

This study aimed to elucidate how the modulation of nociceptive input in the brainstem changes from noon to midnight. Insights into the mechanism of these fluctuations could allow for new hypotheses about the pathophysiology of cluster headache.

METHODS

This repeated measure observational study was conducted at the University Hospital Zurich from December 2019 to November 2022. Healthy adults between 18 and 85 years of age were eligible. All participants were examined at noon and midnight. We tested the pain threshold on both sides of the foreheads with quantitative sensory testing, assessed tiredness levels, and obtained high-field (7 Tesla) and high-resolution functional magnetic resonance imaging (MRI) at each visit. Functional connectivity was assessed at the two visits by performing a region-of-interest analysis. We defined nuclei in the brainstem implicated in processing nociceptive input as well as the thalamus and suprachiasmatic nucleus as the region-of-interest.

RESULTS

Ten people were enrolled, and seven participants were included. First, we did not find statistically significant differences between noon and midnight of A-delta-mediated pain thresholds (median mechanical pain threshold at noon: left 9.2, right 9.2; at night: left 6.5, right 6.1). Second, after correction for a false discovery rate, we found changes in the mechanical pain sensitivity to have a statistically significant effect on changes in the functional connectivity between the left parabrachial nucleus and the suprachiasmatic nucleus (T = -40.79).

CONCLUSION

The MRI data analysis suggested that brain stem nuclei and the hypothalamus modulate A-delta-mediated pain perception; however, these changes in pain perception did not lead to statistically significantly differing pain thresholds between noon and midnight. Hence, our findings shed doubt on our hypothesis that the physiologic circadian rhythmicity of pain thresholds could drive the circadian rhythmicity of cluster headache attacks.

How does circadian rhythm affect postoperative pain after pediatric acute appendicitis surgery?

BACKGROUND

This study aimed to evaluate the relationship between postoperative pain and circadian rhythm after pediatric acute appendicitis surgery.

METHODS

Two hundred patients, aged 6-18 years, undergoing acute appendicitis surgery were included in this prospective observational study. The patients were divided into four groups according to the time they underwent surgery: the night group, 01:01-07:00; morning group, 07:01-13:00; afternoon group, 13:01-19:00; and evening group, 19:01-01:00. Intraoperative and postoperative vital signs, postoperative 24-h Wong-Baker Faces Pain Rating Scale (FACEs) scores, and the amount of analgesic required were recorded.

RESULTS

A total of 186 patients were analyzed in the study. There was no statistically significant difference in the demographic characteristics of the patient groups. Additionally, no differences were observed in intraoperative and postoperative vital signs among the four groups. However, patients in the night group had significantly higher FACEs values than those in the other groups at each time point (1st, 3rd, 6th, and 12th h) up to 12 h (P = 0.007, P = 0.023, P = 0.048, and P = 0.003, respectively). The amount of analgesic required in the night group was statistically higher than in the other groups until 12 h (P = 0.002, P < 0.001, P = 0.002, and P = 0.004, respectively).

CONCLUSIONS

A relationship was found between acute appendicitis operations performed at night (01:01 to 07:00) under general anesthesia and circadian rhythm in children. We believe that considering circadian time in the relief of postoperative pain would be beneficial.

Suppression of neuropathic pain in the circadian clock-deficient Per2m/m mice involves up-regulation of endocannabinoid system

Neuropathic pain often results from injuries and diseases that affect the somatosensory system. Disruption of the circadian clock has been implicated in the exacerbation of the neuropathic pain state. However, in this study, we report that mice deficient in a core clock component Period2 (Per2m/m mice) fail to develop tactile pain hypersensitivity even following peripheral nerve injury. Similar to male wild-type mice, partial sciatic nerve ligation (PSL)-Per2m/m male mice showed activation of glial cells in the dorsal horn of the spinal cord and increased expression of pain-related genes. Interestingly, α1D-adrenergic receptor (α1D-AR) expression was up-regulated in the spinal cord of Per2m/m mice, leading to increased production of 2-arachidonoylglycerol (2-AG), an endocannabinoid receptor ligand. This increase in 2-AG suppressed the PSL-induced tactile pain hypersensitivity. Furthermore, intraspinal dorsal horn injection of adeno-associated viral vectors expressing α1D-AR also attenuated pain hypersensitivity in PSL-wild-type male mice by increasing 2-AG production. Our findings reveal an uncovered role of the circadian clock in neuropathic pain disorders and suggest a link between α1D-AR signaling and the endocannabinoid system.

Fentanyl in cancer pain management: avoiding hasty judgments and discerning its potential benefits

Cancer pain is an important challenge in treatment and requires a rapid onset of action for its control. In particular, breakthrough cancer pain (BTcP) should be adequately controlled with a stable dose of a short-acting oral opioid. Fentanyl is a synthetic, highly selective opioid with many advantageous chemical properties, including high lipophilicity and distinct pharmacokinetic properties. It is recommended for pain management in a variety of settings, including acute pain, chronic pain and BTcP. To date, its variously designed formulations allow non-invasive administration; amongst others, sublingual fentanyl has proven useful in the management of BTcP and in improving the quality of life of patients with cancer. This review provides an update on the management of BTcP with fentanyl, with consideration of safety, as it remains an important tool in the treatment of cancer pain.

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.

Retrospective Observational Study on the Characteristics of Pain and Associated Factors of Breakthrough Pain in Advanced Cancer Patients

Objective

This study aimed to conduct a retrospective observational study to understand the status of characteristics of pain and identify potential variables influencing the clinical presentation of breakthrough cancer pain (BTP) in advanced cancer patients.

Methods

Advanced cancer patients over 18 years of age; diagnosed with cancer of any type and stage III or IV in the palliative care ward with available data were enrolled between 2018 and 2020. Demographic data and pain-related information were collected by using structured electronic extraction form from Hospital Information System (HIS). Patients who had well-controlled background pain with an intensity ≤4 on a 0–10 numerical scale for >12 hours/day, the presence of transient exacerbations of pain with moderate-severe intensity (≧5), and clearly distinguish from background pain were regarded to have suffered BTP. Spearman correlation was conducted to explore the relationship between pain score and demographics characteristics. Factors significant in univariate analysis were included in the multiple regression model to explore independent predictive factors associated with the BTP.

Results

Of 798 advanced cancer patients, the mean age was 56.7 (SD = 11.84) years. Lung cancer (29.95%) was the most common cancer, and pain (93%) was the most common symptom. More than half (n = 428, 53.6%) of the patients experienced BTP. The median number of BTP episodes was 4 (IQR = 2, 7, range: 1–42). The median intensity of BTP was 6 (IQR = 6, 7, range 5–10). Patients with severe background pain or BTP had longer hospital stay and more symptoms. Besides, more severe background pain was related to higher activity of daily living. Intramuscular injection of hydromorphone hydrochloride was the main medication for BTP onset. Younger age, background pain, anorexia, and constipation were independently associated with the presentation of BTP. BTP pain intensity was independently associated with bloating. Symptom numbers were an independent factor and positively associated with BTP episodes.

Conclusions

BTP resulted in poor prognosis, which has a variable presentation depending on interdependent relationships among different characteristics. Good controlling of background pain and assessment of pain-related symptoms are essential for BTP management. BTP should be managed individually, especially the invisible pain among aged patients. Furthermore, BTP-related education and training were still needed.

Current management of cancer pain in Italy: Expert opinion paper

Introduction

Chronic pain and breakthrough cancer pain (BTcP) have a high prevalence in all cancer types and cancer stages, combined with a significant physical, psychological, and economic burden. Despite efforts to improve appropriate management of cancer pain, a poor assessment and guilty undertreatment are still reported in many countries. The purpose of this expert opinion paper is to contribute to reduce and clarify these issues with a multidisciplinary perspective in order to share virtuous paths of care.

Methods

Common questions about cancer pain assessment and treatment were submitted to a multidisciplinary pool of Italian clinicians and the results were subsequently discussed and compared with the findings of the published literature.

Conclusion

Despite a dedicated law in Italy and effective treatments available, a low percentage of specialists assess pain and BTcP, defining the intensity with validated tools. Moreover, in accordance with the findings of the literature in many countries, the undertreatment of cancer pain is still prevalent. A multidisciplinary approach, more training programs for clinicians, personalised therapy drug formulations, and virtuous care pathways will be essential to improve cancer pain management.

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.

Breakthrough cancer pain in 2020

PURPOSE OF REVIEW

An overview on breakthrough cancer pain (BTCP), including inherent limitations of the terminology, assessment, clinical presentation, and treatment options.

RECENT FINDINGS

The estimated prevalence of BTCP is dependent on the defined cutoffs for controlled background pain and the magnitude of the pain flare. In addition, pain flares outside the definition of BTCP are prevalent. In the 11th Revision of the International Classification of Diseases, the temporal characteristics of cancer pain are described as continuous background pain and intermittent episodic pain. BTCP should be assessed by validated methods, and the patient perspective should be included. The pain may be related to neoplastic destruction of bone, viscera, or nerve tissue and is characterized by rapid onset, high intensity, and short duration. Treatment directed towards painful metastases must be considered. Due to pharmacological properties mirroring the pain characteristics, transmucosal fentanyl formulations are important for the treatment of BTCP. Oral immediate release opioids can be used for slow-onset or predictable BTCP. For more difficult pain conditions, parenteral, or even intrathecal pain medication, may be indicated.

SUMMARY

All clinically relevant episodic pains must be adequately treated in accordance with the patient's preferences. Transmucosal fentanyl formulations are effective for BTCP.

Endogenous opiates and behavior: 2019

This paper is the forty-second consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2019 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Sulfasalazine alleviates neuropathic pain hypersensitivity in mice through inhibition of SGK-1 in the spinal cord

Diurnal variations in pain hypersensitivity are common in chronic pain disorders. Temporal exacerbation of neuropathic pain hypersensitivity is dependent on diurnal variations in glucocorticoid secretion from the adrenal glands. We previously demonstrated that spinal expression of serum- and glucocorticoid-inducible kinase-1 (SGK-1) is associated with glucocorticoid- induced exacerbation of pain hypersensitivity, but there are no available strategies to inhibit SGK-1 in the spinal cord. By screening a clinically approved drug library (more than 1,200 drugs), we found that sulfasalazine (SSZ) has inhibitory effects on SGK-1. SSZ is a prodrug composed of 5-aminosalicylic acid and sulfapyridine linked by NN bond, which is therapeutically effective for inflammatory bowel diseases. However, the NN bond in SSZ was necessary for its inhibitory action against SGK-1. Although intrathecal injection of SSZ to nerve-injured mice significantly alleviated mechanical pain hypersensitivity, no significant anti- neuropathic pain effects of SSZ were detected after oral administration due to its low bioavailability and limited spinal distribution, which were associated with efflux by the xenobiotic transporter breast cancer resistance protein (BCRP). Concomitant oral administration of SSZ with febuxostat (FBX), which is an approved drug to inhibit BCRP, improved the distribution of SSZ to the spinal cord. The concomitant oral administration with FBX also increased the anti-neuropathic pain effects of SSZ. Our study revealed a previously unrecognized pharmacological effect of SSZ to alleviate SGK-1-induced painful peripheral neuropathy, and concomitant oral administration of SSZ with FBX may also be a preventative option for diurnal exacerbation of neuropathic pain hypersensitivity.

Characteristics of Breakthrough Pain and Its Impact on Quality of Life in Terminally Ill Cancer Patients

Purpose. This study aimed to characterize breakthrough pain (BTP) and investigate its impact on quality-of-life (QoL) in terminally-ill cancer patients. Similarities and differences between high and low predictable BTP were also tested. Methods. Secondary analysis of a multicenter longitudinal observational study included 92 patients at their end-of-life. BTP was assessed with a short form of the Italian version of the Alberta Breakthrough Pain Assessment Tool. QoL was assessed with the Palliative Outcome Scale (0-40). Patients were stratified by self-reported BTP predictability into unpredictable BTP (never or rarely able to predict BTP) and predictable BTP (sometimes to always able to predict BTP). Results. In all, 665 BTP episodes were recorded (median 0.86 episodes/day). A median duration of 30 minutes and a median peak intensity score of 7 out of 10 were reported. Time to peak was <10 minutes, 10 to 30 minutes, and ≥30 minutes in 267 (41.1%), 259 (39.9%), and 30 (4.6%) of the episodes, respectively. Onset of relief occurred after a median of 30 minutes. Time to peak (P < .001) and duration (P = .046) of BTP was shorter in patients with predictable pain (n = 31), who usually were younger than those with unpredictable pain (P = .03). The mean (SD) QoL score was 14.6 (4.6). No difference in QoL between patients with predictable and unpredictable BTP was found (P = .49). Conclusions. In terminally-ill cancer patients, BTP is a severe problem with a negative impact on QoL and has different characteristics according to its predictability.