The prevalence of neuropathic pain is high after treatment for breast cancer: a systematic review

Persistent Pain After Breast Cancer Treatment, an Underreported Burden for Breast Cancer Survivors

BACKGROUND

Many patients who have undergone surgery experience persistent pain after breast cancer treatment (PPBCT). These symptoms often remain unnoticed by treating physician(s), and the pathophysiology of PPBCT remains poorly understood. The purpose of this study was to determine prevalence of PPBCT and examine the association between PPBCT and various patient, tumor, and treatment characteristics.

PATIENTS AND METHODS

We conducted a questionnaire-based cross-sectional study enrolling patients with breast cancer treated at Máxima Medical Center between 2005 and 2016. PPBCT was defined as pain in the breast, anterior thorax, axilla, and/or medial upper arm that persists for at least 3 months after surgery. Tumor and treatment characteristics were derived from the Dutch Cancer Registry and electronic patient files.

RESULTS

Between February and March 2019, a questionnaire was sent to 2022 women, of whom 56.5% responded. Prevalence of PPBCT among the responders was 37.9%, with 50.8% reporting moderate to severe pain. Multivariable analyses showed that women with signs of anxiety, depression or a history of smoking had a higher risk of experiencing PPBCT. Women aged 70 years or older at diagnosis were significantly less likely to report PPBCT compared with younger women. No significant association was found between PPBCT and treatment characteristics, including type of axillary surgery and radiotherapy.

CONCLUSIONS

A considerable percentage of patients with breast cancer experience PPBCT. Women with signs of anxiety or depression and women with a history of smoking are more likely to report PPBCT. Further research is required to understand the underlying etiology and to improve prevention and treatment strategies for PPBCT.

Neuropathic Pain Affects Quality of Life in Breast Cancer Survivors with Chemotherapy-Induced Peripheral Neuropathy

BACKGROUND

Despite the significant impact of chemotherapy-induced peripheral neuropathy on the quality of life for breast cancer survivors, there is a notable lack of comprehensive research. Therefore, a crucial need exists for further systematic investigation and inquiry into this matter.

AIMS

This study examined predictors of quality of life in breast cancer survivors with chemotherapy-induced peripheral neuropathy.

DESIGN

A cross-sectional, correlational design.

SETTINGS

This study was conducted at a medical center in northern Taiwan and a teaching hospital in northeastern Taiwan.

PARTICIPANTS/SUBJECTS

One hundred and thirty adult women with breast cancer, who have undergone chemotherapy and obtained a Total Neuropathy Scale-Clinical Version score>0, were enrolled.

METHODS

Neuropathic pain, sleep disturbances, depression, and quality of life were evaluated using multiple regression analysis to identify quality of life predictors. Clinical importance was established using the minimally important difference of Functional Assessment of Cancer Therapy-Breast.

RESULTS

The study indicated that improving depression (B = -10.87, p < .001) and neuropathic pain (B = -8.33, p = .004) may enhance the quality of life of breast cancer survivors with chemotherapy-induced peripheral neuropathy. Moreover, the individual's marital status and family history of breast cancer were identified as predictive factors.

CONCLUSIONS

This study illuminates quality of life determinants for breast cancer survivors with chemotherapy-induced peripheral neuropathy, advocating comprehensive care and addressing depression and neuropathic pain for better outcomes.

NT5DC2 knockdown suppresses progression, glycolysis, and neuropathic pain in triple-negative breast cancer by blocking the EGFR pathway

Triple-negative breast cancer (TNBC) is an exceptionally aggressive breast cancer subtype associated with neuropathic pain. This study explores the effects of 5'-nucleotidase domain-containing protein 2 (NT5DC2) on the progression of TNBC and neuropathic pain. Microarray analysis was conducted to identify differentially expressed genes in TNBC and the pathways involved. Gain- and loss-of-function assays of NT5DC2 were performed in TNBC cells, followed by detection of the extracellular acidification rate, adenosine triphosphate (ATP) levels, lactic acid production, glucose uptake, proliferation, migration, and invasion in TNBC cells. Macrophages were co-cultured with TNBC cells to examine the release of polarization-related factors and cytokines. A xenograft tumor model was established for in vivo validation. In addition, a mouse model of neuropathic pain was established through subepineural injection of TNBC cells, followed by measurement of the sciatic functional index and behavioral analysis to assess neuropathic pain. NT5DC2 was upregulated in TNBC and was positively correlated with epidermal growth factor receptor (EGFR). NT5DC2 interacted with EGFR to promote downstream signal transduction in TNBC cells. NT5DC2 knockdown diminished proliferation, migration, invasion, the extracellular acidification rate, ATP levels, lactic acid production, and glucose uptake in TNBC cells. Co-culture with NT5DC2-knockdown TNBC cells alleviated the M2 polarization of macrophages. Furthermore, NT5DC2 knockdown reduced tumor growth and neuropathic pain in mice. Importantly, activation of the EGFR pathway counteracted the effects of NT5DC2 knockdown. NT5DC2 knockdown protected against TNBC progression and neuropathic pain by inactivating the EGFR pathway.

Assessment of neuropathic pain following cancer treatment

Neuropathic cancer pain (NCP) is prevalent affecting up to 58% of those with persistent pain following cancer treatment. Neuropathic pain can develop from malignancy, after neural tissue insult during surgery and/or exposure to radiation or neurotoxic agents used as part of cancer treatment regimens. Pain following cancer treatment is commonly under-treated and one barrier identified is poor recognition of pain and inadequate assessment. Recognition of the presence of NCP is important to inform pain management, which is challenging to treat and warrants the use of specific treatments to target neuropathic mechanisms. In this review, approaches for screening and classifying NCP are described. These include screening questionnaires and the application of the updated neuropathic pain grading system in a cancer context. The evidence from neuropathic pain related assessments in cancer populations is provided and highlighted under different neuropathic pain grades. Recommendations for assessment in practice are provided.

Neuropathic pain after surgery - A clinical validation study and assessment of accuracy measures of the 5-item NeuPPS scale

OBJECTIVE

The aim of this study was to validate the Neuropathic Pain for Post-Surgical Patients (NeuPPS) scale against clinically verified neuropathic pain (NP) by quantitative sensory testing (QST) as well as evaluation of other psychometric properties. The NeuPPS is a validated 5-item scale designed to evaluate NP in surgical populations.

METHODS

Data from 537 women aged >18 years scheduled for primary breast cancer surgery enrolled in a previous study for assessing risk factors for persistent pain after breast cancer treatment were used. Exclusion criteria were any other breast surgery or relevant comorbidity. A total of 448 eligible questionnaires were available at 6 months and 455 at 12 months. At 12 months, 290 patients completed a clinical examination and QST. NeuPPS and PainDETECT were analyzed against patients with and without clinically verified NP. NP was assessed using a standardized QST protocol including a clinical assessment. Furthermore, the NeuPPS and PainDETECT scores were psychometrically tested with an item response theory method, the Rasch analysis, to assess construct validity. Primary outcomes were the diagnostic accuracy measures for the NeuPPS, and secondary measures were psychometric analyses of the NeuPPS after 6 and 12 months. PainDETECT was also compared to clinically verified NP as well as NeuPPS comparing the stability of the estimates.

RESULTS

Comparing the NeuPPS scores with verified NP using a receiver operating characteristic curve, the NeuPPS had an area under the curve of 0.80. Using a cutoff of 1, the NeuPPS had a sensitivity of 88% and a specificity of 59%, and using a cutoff of 3, the values were 35 and 96%, respectively. Analysis of the PainDETECT indicated that the used cutoffs may be inappropriate in a surgical population.

CONCLUSION

The present study supports the validity of the NeuPPS as a screening tool for NP in a surgical population.

Cancer-Related Neuropathic Pain, Chemotherapy-Induced Peripheral Neuropathy and Cognitive Decline in a 5-Year Prospective Study of Patients with Breast Cancer-NEON-BC

This study aims to estimate the prevalence and to identify the determinants of cancer-related neuropathic pain (CRNP), chemotherapy-induced peripheral neuropathy (CIPN) and cognitive decline among patients with breast cancer over five years after diagnosis. Women with an incident breast cancer (n = 462) and proposed for surgery were recruited at the Portuguese Institute of Oncology-Porto in 2012 and underwent systematic neurological examinations and evaluations with the Montreal Cognitive Assessment (MoCA) before treatment and after one, three, and five years. Multivariate logistic regression was used to assess the determinants of CRNP and CIPN, and multivariate linear regression for the variation in MoCA scores. Prevalence of CRNP and CIPN decreased from the first to the fifth year after diagnosis (CRNP: from 21.1% to 16.2%, p = 0.018; CIPN: from 22.0% to 16.0% among those undergoing chemotherapy, p = 0.007). Cognitive impairment was observed in at least one assessment in 17.7% of the women. Statistically significant associations were observed between: cancer stage III and both CRNP and CIPN; triple negative breast cancer, chemotherapy, axillary node dissection, older age, higher education, and being single and CRNP; taxanes and fruit and vegetable consumption and CIPN. Anxiety, depression and poor sleep quality at baseline were associated with decreases in MoCA values from pre- to post-treatment and with CRNP. Follow-up protocols should consider the persistence of CRNP, CIPN, and cognitive impairment for several years following diagnosis.

Anti HER-2 aptamer functionalized gold nanoparticles of dasatinib for targeted chemo-radiotherapy in breast cancer cells

In the present study, gold nanoparticles functionalized with anti HER-2 aptamer were designed for effective targeted delivery of dasatinib (DSB) to breast cancer cells. Anti HER-2 aptamer attached to porous or plain gold nanoparticles were compared for dasatinib delivery. Activated drug with succinic anhydride and L-cysteine linker was used for conjugation of DSB to gold nanoparticles. The loading efficiency of the activated drug on plain and porous gold nanoparticles was 52 and 68 %, respectively, which was significantly more than the loading of free DSB in gold nanoparticles (1-2.5 %). The anti HER-2 aptamer was conjugated to porous gold nanoparticles loaded with the activated drug. Various characterization techniques such as FESEM, TEM, AFM, zeta potential and ICP-MS were used to confirm the binding of the drug to gold nanoparticles. 1HNMR and FTIR spectroscopic analyses were employed to examine the structural characteristics of the conjugated drug. These analytical techniques confirmed the successful incorporation of succinyl and thiol groups onto the drug molecule. The amount of aptamer binding to different types of gold nanoparticles was obtained from the intensity of the light emitted from the bands observed in electrophoresis gel and due to the presence of porosity in porous gold nanoparticles, the amount of aptamer conjugation on porous gold nanoparticles increased compared to plain ones. Cell cytotoxicity and cellular uptake were evaluated by MTT assay and TEM in BT-474 and MCF-7 cells. Aptamer-functionalized porous gold nanoparticles containing activated dasatinib showed higher cytotoxicity and cellular uptake than modified DSB-loaded nanoparticles and un-activated DSB. The combination of radiation therapy with the modified dasatinib attached to porous gold nanoparticles and aptamer demonstrated a notable reduction in the IC50 values for both the BT-474 and MCF-7 cell lines. Specifically, the IC50 value for the BT-474 cells decreased from 6.95 μM (for unmodified dasatinib) to 2.57 μM, while for the MCF-7 cells, it decreased from 13.97 μM to 8.57 μM. These findings indicate a significant improvement in the efficacy of the modified dasatinib compared to its unmodified counterpart when used in conjunction with radiation therapy.

A Review on the Management of Peripheral Neuropathic Pain Following Breast Cancer

Postmastectomy pain syndrome (PMPS) is a common and debilitating form of postsurgical pain with neuropathic characteristics, presenting as burning, stabbing, or pulling sensations after mastectomy, lumpectomy, or other breast procedures. With a prevalence of 31%, the risk factors for PMPS include younger age, psychosocial factors, radiotherapy, axillary lymph node dissection, and a history of chronic pain. This review evaluates the pharmacological and surgical options for managing PMPS. Pharmacological treatment options include antidepressants, gabapentinoids, levetiracetam, capsaicin, and topical lidocaine. Procedural and surgical options include fat grafting, nerve blocks, radiofrequency ablation, peripheral nerve surgery, serratus plane block, and botulinum toxin injections. Despite the variety of therapeutic options available for patients, further randomized trials are required to conclude whether these treatments reduce the intensity of neuropathic pain in patients with PMPS. In particular, comparative studies and the inclusion of patients across a range of pain intensities will be essential to developing a treatment algorithm for PMPS. In conclusion, current management for these patients should be tailored to their individual requirements.

Effect of Pain Coping Skills Training on Pain and Pain Medication Use for Women With Breast Cancer

CONTEXT

Pain is distressing for women with breast cancer. Pain medication may not provide full relief and can have negative side-effects. Cognitive-behavioral pain intervention protocols reduce pain severity and improve self-efficacy for pain management. These interventions' impact on pain medication use is less clear. Intervention length and coping skills use might play a role in pain outcomes.

OBJECTIVES

Secondary analysis to examine differences in pain severity, pain medication use, pain self-efficacy, and coping skill use after five- and one-session cognitive-behavioral pain intervention protocols. Pain self-efficacy and coping skills use were assessed as mediators of intervention effects on pain and pain medication use.

METHODS

Women (N = 327) with stage I-III breast cancer were enrolled in a randomized trial comparing individually-delivered, five- and one-session pain coping skills training (PCST). Pain severity, pain medication use, pain self-efficacy, and coping skills use were assessed preintervention and five to eight weeks later (postintervention).

RESULTS

Pain and pain medication use significantly decreased, while pain self-efficacy increased pre-post for women randomized to both conditions (P's <.05). Five-session PCST participants demonstrated less pain (P =.03) and pain medication use (P =.04), and more pain self-efficacy (P =.02) and coping skills use (P =.04) at postintervention compared to one-session PCST participants. Pain self-efficacy mediated the relationship of intervention condition with pain and pain medication use.

CONCLUSION

Both conditions led to improvements in pain, pain medication use, pain self-efficacy, and coping skills use, and 5-session PCST showed the greatest benefits. Brief cognitive-behavioral pain intervention improve pain outcomes, and pain self-efficacy may play a role in these effects.

Kinin B1 and B2 receptors mediate cancer pain associated with both the tumor and oncology therapy using aromatase inhibitors

Pain caused by the tumor or aromatase inhibitors (AIs) is a disabling symptom in breast cancer survivors. Their mechanisms are unclear, but pro-algesic and inflammatory mediators seem to be involved. Kinins are endogenous algogenic mediators associated with various painful conditions via B₁ and B₂ receptor activation, including chemotherapy-induced pain and breast cancer proliferation. We investigate the involvement of the kinin B₁ and B₂ receptors in metastatic breast tumor (4T1 breast cancer cells)-caused pain and in aromatase inhibitors (anastrozole or letrozole) therapy-associated pain. A protocol associating the tumor and antineoplastic therapy was also performed. Kinin receptors' role was investigated via pharmacological antagonism, receptors protein expression, and kinin levels. Mechanical and cold allodynia and muscle strength were evaluated. AIs and breast tumor increased kinin receptors expression, and tumor also increased kinin levels. AIs caused mechanical allodynia and reduced the muscle strength of mice. Kinin B₁ (DALBk) and B₂ (Icatibant) receptor antagonists attenuated these effects and reduced breast tumor-induced mechanical and cold allodynia. AIs or paclitaxel enhanced breast tumor-induced mechanical hypersensitivity, while DALBk and Icatibant prevented this increase. Antagonists did not interfere with paclitaxel's cytotoxic action in vitro. Thus, kinin B₁ or B₂ receptors can be a potential target for treating the pain caused by metastatic breast tumor and their antineoplastic therapy.

Pain Treatment and Cancer Patients: Are we Heeding Quality of Life?

The use of opioid analgesics remains the primary therapy for pain control in cancer patients. However, ample evidence persists showing that treatment is still inadequate. This cross-sectional study was carried out during one year in a Brazilian Cancer Hospital to evaluate the impact of opioid use on analgesia and patients' quality of life. The Pain Management Index (PMI), EORTC QLQ.C30 (Quality of Life of Cancer Patients), Karnofsky Performance Status (KPS), Douleur Neuropathique 4 (DN4), and Brief Pain Inventory-Short Form (BPI-SF) were used. A hundred patients with advanced solid tumors and using opioids were included, with 82% of them reporting daily pain with 58% having intense pain. Morphine with a mean dose of 49 Morphine Milligram Equivalent were used by 57% of them, and PMI was negative in 34% of the sample. Neuropathic pain was found in 72% of patients. The pain was related to all BPI variables. Despite the substantial negative impact of pain on QOL, no association was found between the clinical factors assessed and QOL itself. This gap can be related to the persistence of high levels of sub-treatment, depression, and neuropathic pain associated with the use of low doses of opiates and adjuvant medications in the sample.

High-rate breakthrough cancer pain and tumour characteristics - literature review and case series

Cancer pain requires careful comprehensive patient evaluation and an appropriate and personalized clinical approach by a trained multidisciplinary team. The proper assessment of breakthrough cancer pain (BTcP) is part of an all-inclusive multidimensional evaluation of the patient. The aim of this narrative review is to explore the relationship between high-rate BTcP, which strongly impacts health- related quality of life and tumour characteristics, in the face of novel approaches that should provide guidance for future clinical practice. The presentation of short, emblematic clinical reports also promotes knowledge of BTcP, which, despite the availability of numerous therapeutic approaches, remains underdiagnosed and undertreated. This article is part of the Management of breakthrough cancer pain Special Issue: https://www.drugsincontext.com/special_issues/management-of-breakthrough-cancer-pain.

Role of self-efficacy for pain management and pain catastrophizing in the relationship between pain severity and depressive symptoms in women with breast cancer and pain

PURPOSE

This study evaluated the relationship between pain and depressive symptoms through pain self-efficacy and pain catastrophizing in breast cancer patients with pain.

DESIGN

Secondary analysis of a randomized trial investigating a cognitive-behavioral pain management protocol.

SAMPLE

Females (N = 327) with stage I-III breast cancer and report of at least moderate pain.

METHODS

Pain severity, pain self-efficacy, pain catastrophizing, and depressive symptoms were measured. The proposed model was assessed using structural equation modeling.

RESULTS

Higher pain severity was significantly related to lower pain self-efficacy and higher pain catastrophizing. Lower pain self-efficacy and higher pain catastrophizing were significantly related to more depressive symptoms. Higher pain severity was significantly associated with more depressive symptoms through lower pain self-efficacy and higher pain catastrophizing. The association between pain severity and depressive symptoms was not significant when specified as a direct effect.

CONCLUSION

Pain severity related to depressive symptoms in breast cancer patients via pain self-efficacy and pain catastrophizing.

IMPLICATIONS FOR PSYCHOSOCIAL PROVIDERS

Measurement of pain self-efficacy and pain catastrophizing should be incorporated into comprehensive pain assessments for women with breast cancer, as these variables may be relevant therapeutic targets. Psychosocial symptom management interventions should include strategies that increase pain self-efficacy and decrease pain catastrophizing because these pain-related cognitive variables appear to drive the relationship between pain severity and depressive symptoms.

A Delphi Study on the Management of Neuropathic Cancer Pain in Spain: The DOLNEO Study

Purpose

The objectives of this project were to assess the current situation and management of cancer-related neuropathic pain (CRNP) in Spain and to provide specific recommendations for the assessment, diagnosis and treatment of CRNP using a Delphi methodology.

Methods

This was a qualitative study that followed a Delphi methodology using a questionnaire with 56 statements that were grouped into 5 areas related to CRNP: prevalence and impact, pathophysiology, assessment and diagnosis, specific syndromes, treatment, and multidisciplinary approach. Based on the responses, the scientific committee prepared an algorithm and a recommended pathway for the management of CRNP.

Results

Seventy-nine physicians attended the meeting and completed the questionnaire. Consensus was reached for all statements relating to the prevalence and impact of CRNP. However, the perceptions of specialists from palliative care of the frequency and impact of CRNP differed from those of other specialists. A high degree of consensus was reached for all statements concerning the assessment and diagnosis of CRNP. Regarding specific syndromes, the only statement with a lack of consensus was that on the frequency of NP in patients undergoing radiotherapy. There were some disagreements regarding the multidisciplinary approach and referral criteria for the management of NP.

Conclusion

Our results show a large degree of agreement on the assessment, diagnosis and treatment of cancer-related neuropathic pain among the specialists involved in its management. There were, however, some disagreements regarding the multidisciplinary approach and referral criteria for the management of neuropathic pain.

Changes in Pain Sensitivity in Treatment for Breast Cancer: A 12-Month Follow-Up Case Series

This study aimed to investigate changes in the pain sensory profile of women with breast cancer. Five women with unilateral breast cancer were enrolled. Participants were assessed with direct (quantitative sensory testing, QST) and indirect measures of pain sensitization (self-reported central sensitization inventory, CSI) at baseline (before surgery), 1 week after surgery, and at 1, 6, 9, and 12 months post-surgery. In the event of pain occurrence, the Leeds Assessment of Neuropathic Symptoms and Signs was also used. Nociceptive pain was the predominant pain mechanism in the postoperative period, while an increase in sensitization predominated one year after breast cancer surgery, especially in those participants who had received more treatment procedures. The participants who received more therapies for breast cancer experienced persistent pain and a higher level of sensitization. An assessment protocol including direct measurements (QST) and indirect measurement (self-reported CSI) allows for detecting changes in pain sensitivity, which can be useful for characterizing and/or predicting pain before, during, and up to one year following surgical interventions for breast cancer.

Machine-Learning Analysis of Serum Proteomics in Neuropathic Pain after Nerve Injury in Breast Cancer Surgery Points at Chemokine Signaling via SIRT2 Regulation

Background: Persistent postsurgical neuropathic pain (PPSNP) can occur after intraoperative damage to somatosensory nerves, with a prevalence of 29–57% in breast cancer surgery. Proteomics is an active research field in neuropathic pain and the first results support its utility for establishing diagnoses or finding therapy strategies. Methods: 57 women (30 non-PPSNP/27 PPSNP) who had experienced a surgeon-verified intercostobrachial nerve injury during breast cancer surgery, were examined for patterns in 74 serum proteomic markers that allowed discrimination between subgroups with or without PPSNP. Serum samples were obtained both before and after surgery. Results: Unsupervised data analyses, including principal component analysis and self-organizing maps of artificial neurons, revealed patterns that supported a data structure consistent with pain-related subgroup (non-PPSPN vs. PPSNP) separation. Subsequent supervised machine learning-based analyses revealed 19 proteins (CD244, SIRT2, CCL28, CXCL9, CCL20, CCL3, IL.10RA, MCP.1, TRAIL, CCL25, IL10, uPA, CCL4, DNER, STAMPB, CCL23, CST5, CCL11, FGF.23) that were informative for subgroup separation. In cross-validated training and testing of six different machine-learned algorithms, subgroup assignment was significantly better than chance, whereas this was not possible when training the algorithms with randomly permuted data or with the protein markers not selected. In particular, sirtuin 2 emerged as a key protein, presenting both before and after breast cancer treatments in the PPSNP compared with the non-PPSNP subgroup. Conclusions: The identified proteins play important roles in immune processes such as cell migration, chemotaxis, and cytokine-signaling. They also have considerable overlap with currently known targets of approved or investigational drugs. Taken together, several lines of unsupervised and supervised analyses pointed to structures in serum proteomics data, obtained before and after breast cancer surgery, that relate to neuroinflammatory processes associated with the development of neuropathic pain after an intraoperative nerve lesion.

Peripheral Neuropathic Pain Following Breast Cancer: Effectiveness and Tolerability of High-Concentration Capsaicin Patch

Purpose

Data supporting the use of high-concentration capsaicin patches (HCCPs) in breast cancer (BC) patients and BC survivors (BCSs) with peripheral neuropathic pain (PNP) are limited. This observational study evaluated the effectiveness and safety of HCCP applications in BCSs/BC patients with PNP.

Patients and Methods

Data from all patients treated with HCCP in the pain department of a French comprehensive cancer centre were collected from 01-Jan-2014 to 14-Oct-2020. Independent pain specialists completed the Clinical Global Impression of Change (CGIC) for each included patient based on data extracted from patient’s electronic medical record compiled by the treating pain specialist after each HCCP application.

Results

Patients (N=279; mean age: 59.2 years; previous history of PNP medication: 54.5%) received on average 4.1 repeated HCCP applications (1141 HCCP applications); 68.8% received HCCP as an add-on to systemic therapy and 27.9% as first-line therapy. PNP was most frequently caused by surgery (62.4%) followed by chemotherapy (11.8%) and radiotherapy (6.5%). A complete or important analgesic effect was reported at least once by 82.3% of patients. A 6.0% reported no effect at all. For post-surgical PNP existing for <12 months and >10 years an important or complete effect was observed for 70.7% and 56.0% of applications. For chemotherapy- or radiotherapy-induced PNP, this important or complete effect was observed for 52.7% and 52.3% of applications, respectively. HCCP application was associated with site reactions in 54.4% of patients (mainly burning sensation or pain, 45.9%, or erythema, 30.8%) and high blood pressure in 7.2%.

Conclusion

This real-world chart review provides important effectiveness and safety information to clinicians when considering topical options to treat PNP in BCSs/BC patients.

Pain, numbness, or both? Distinguishing the longitudinal course and predictors of positive, painful neuropathic features vs numbness after breast cancer surgery

Supplemental Digital Content is Available in the Text. Examining the divergence of prevalence and predictors of postsurgical numbness vs positive neuropathic symptoms gives insights into variation in clinical postoperative pain experienced by patients.

Introduction:

Both positive (burning, stabbing, and allodynia) and negative (numbness) neuropathic symptoms may arise after surgery but likely contribute differently to patients' postoperative pain experience. Numbness has been identified as divergent from positive neuropathic symptoms and therefore excluded from some neuropathic assessment tools (Neuropathic Pain Scale for PostSurgical patients [NeuPPS]).

Objectives:

In this prospective longitudinal study of patients undergoing breast surgery, we aimed to delineate the time course of numbness and its coincidence with NeuPPS and to contrast the association of surgical, psychosocial, and psychophysical predictors with the development of negative vs positive neuropathic symptoms.

Methods:

Patients reported surgical area sensory disturbances at 2 weeks and 3, 6, and 12 months postoperatively. Association of baseline demographic, surgical, psychosocial, and psychophysical factors with NeuPPS and numbness across time was investigated using generalized estimating equation linear and logistic regression.

Results:

Numbness was consistently reported by 65% of patients; positive neuropathic symptoms were less common, often decreasing over time. Neuropathic Pain scale for PostSurgical patients and numbness co-occurred in half of patients and were both associated with greater clinical pain severity and impact, younger age, axillary surgery, and psychosocial factors. More extensive surgery and chemotherapy were only associated with numbness. Conversely, other chronic pain, lower physical activity, perioperative opioid use, negative affect, and lower baseline pressure pain threshold and tolerance were only associated with NeuPPS. Patients reporting numbness alone did not endorse substantial clinical pain.

Conclusions:

Differentiation of predictors, prevalence, and time course of numbness vs NeuPPS in breast surgical patients revealed important distinctions, suggesting that their independent assessment is worthwhile in future studies of postsurgical pain.

Hypnosis Sedation Reduces the Duration of Different Side Effects of Cancer Treatments in Breast Cancer Patients Receiving Neoadjuvant Chemotherapy

Simple Summary

Reducing side effects of cancer treatments is a major challenge for clinicians involved in the management of breast cancer patients. Among patients receiving neoadjuvant chemotherapy followed by surgery, radiotherapy and endocrine therapy, prolonged side effects frequently mentioned are: polyneuropathy, musculoskeletal pain, postoperative pain and cancer-related fatigue. Conventional drugs have proven to be ineffective in treating theses effects, except for postoperative pain. This is the reason why we prospectively tested the impact of hypnosis sedation used as anesthetic technique for breast cancer surgery on the different side effects of cancer treatment. Despite the limitations of this small non-randomized cohort, preliminary results are very encouraging.

Abstract

Background: Reducing side effects of cancer treatments is a major challenge for clinicians involved in the management of breast cancer patients. Methods: We analyzed data from 63 patients (32 in the general anesthesia group and 31 in the hypnosis sedation group) who were included in 1 prospective non-randomized trial evaluating hypnosis sedation in breast cancer treatment. The patients were followed every 3 months for 2 years. All patients received neoadjuvant chemotherapy with 4 cycles of epirubicin and cyclophosphamide followed by taxanes. Thereafter, patients underwent surgery while on general anesthesia or while on hypnosis sedation. Radiotherapy was administered according to institutional guidelines. Endocrine therapy was prescribed if tumors expressed hormone receptors. Prevalence, intensity and duration of polyneuropathy, musculoskeletal pain, postoperative pain and cancer-related fatigue were assessed at each medical visit. Results: Symptoms duration was statistically reduced for polyneuropathy (p < 0.05), musculoskeletal pain (p < 0.05) postoperative pain and cancer-related fatigue (p < 0.05) in the hypnosis group. Conclusion: Despite the limitations of this study (lack of randomization and small size) we conclude that hypnosis sedation may exert a role on different side effects of breast cancer treatment in patients receiving neoadjuvant chemotherapy, mainly by reducing their duration.

Predictive and Preventive Potential of Preoperative Gut Microbiota in Chronic Postoperative Pain in Breast Cancer Survivors

BACKGROUND

Evidence suggests a potential relationship between gut microbiota and chronic postoperative pain (CPP). This study aimed to explore the predictive and preventive potential of preoperative gut microbiota in CPP in breast cancer survivors.

METHODS

In the clinical experiments, we designed a nested case-control study to compared preoperative gut microbiota of breast cancer survivors with and without CPP using 16s rRNA sequencing. The primary outcome was clinically meaningful pain in or around the operative area 3 months after surgery. Logistic prediction models based on previously identified risk factors for CPP in breast cancer survivors were tested with and without differential bacteria to evaluate the model's potential for improvement with the addition of gut microbiota information. In the animal experiments, preoperative fecal microbiota was transplanted from patients with and without CPP to mice, and a spared nerve injury (SNI) model was used to mimic neuropathic pain in CPP. Mechanical hyperalgesia and the expression of markers of spinal microglia and peroxisome proliferator-activated receptor-γ (PPAR-γ) were assessed.

RESULTS

Sixty-six CPP patients and 66 matched controls were analyzed. Preoperative gut microbiota composition was significantly different in the 2 groups at phylus, family, and genera levels. The discrimination of the clinical prediction model (determined by area under the receiver operating characteristic curve) improved by 0.039 and 0.099 after the involvement of differential gut microbiota at the family and genus levels, respectively. After fecal microbiota transplantation (FMT), "CPP microbiota" recipient mice exhibited significantly increased mechanical hyperalgesia and decreased expression of Ppar-γ and arginase-1 (Arg-1) in the spinal cord.

CONCLUSIONS

Preoperative gut microbiota has the potential to predict and prevent the development of CPP and plays a causal role in its development via the PPAR-γ-microglia pathway in the spinal cord. Thus, it could be targeted to develop a prevention strategy for CPP in breast cancer survivors.

The Influence of Hormone Therapy on secondary diabetes mellitus in Breast Cancer: A Meta-analysis

BACKGROUND

Growing evidences have implied that patients with primary breast cancer (BC) were at increased risks of developing diabetes mellitus (DM). However, as a major adjuvant treatment, the influence of hormone therapy (HT) on secondary DM in primary BC remains controversial; we conducted a meta-analysis of existing studies to evaluate the association of hormone therapy and secondary DM.

METHODS

We searched online databases (PubMed, EMBASE, the Cochrane library, Scopus, and Google Scholar) for studies exploring the influence of hormone therapy on secondary DM in BC. The summarized effect sizes (ES) and 95% confidence interval (95% CI) are calculated by STATA software utilizing fixed-effect or random-effect models, depending on the heterogeneity of the eligible studies.

RESULTS

Ultimately, 7 retrospective publications including a total of 44,524 primary BC patients are eligible in present meta-analysis. HT use significantly increased the risk of developing DM in primary BC patients, whenever compared with NON-HT BC patients (pooled adjusted HR 1.30, 95% CI: 1.19-1.43) or NORMAL participants (HR 1.19, 95% CI: 1.14-1.25). As to specific HT medications, our sub-analysis demonstrates the risk for DM in tamoxifen (TAM) users elevates by 30% than NON-TAM use BC patients (pooled HR 1.30, 95% CI: 1.20-1.40) and by 18% than NORMAL participants (pooled HR 1.18, 95% CI: 1.12-1.24). However, for aromatase inhibitors (AIs) users, the risks for DM do not elevate significantly. Funnel plots and Egger's tests are used to evaluate publication bias and no apparent bias is detected in all analysis.

CONCLUSION

The present study is the first meta-analysis which thoroughly reveals that adjuvant HT is a risk factor of secondary DM in primary female BC patients. As to specific HT medications, TAM use significantly enhances the incidence of secondary DM, while AIs use does not influence the DM incidence significantly. Our results can help clinicians to tailor more appropriate strategies for the therapy and follow-up of primary BC patients.

Etiology and epidemiology of neuropathic pain

Background: Neuropathic pain is defined as pain arising as a direct consequence of a lesion or disease affecting the somatosensory system either at the peripheral or central level. In most cases, neuropathic pain is associated with poor general health and has a problem of suboptimal response to medical treatment. This review will discuss the neurologic and non-neurologic conditions that cause neuropathic pain and the results of epidemiologic studies on neuropathic pain.Current Concepts: Epidemiology would be a useful clinical tool for designing management and prevention strategies for various neuropathic pain syndromes. Validated neuropathic pain screening questionnaires are widely used as useful tools for the epidemiologic study of neuropathic pain. There are also validated Korean versions of these questionnaires. The overall prevalence of neuropathic pain was estimated at 6.9-10%. Common neuropathic pain syndromes include diabetic neuropathy, herpes zoster, and trigeminal neuralgia. In addition, neuropathic pain can also occur in central nervous system disorders such as spinal cord injury or stroke, and other conditions like cancerous diseases, intervertebral disc disease, and joint diseases.Discussion and Conclusion: Neuropathic pain does not respond well to medical treatment, which leaves both patients and physicians are less satisfied with such treatments. Therefore, physicians must identify the causes of the pain, explain them to the patient, and proceed with the treatment together with patients.

Effect of physical activity levels on oncological breast surgery recovery: a prospective cohort study

After breast cancer (BC) surgery, women may experience a physical decline. The effect of physical activity (PA) on the course of recovery after BC surgery has not yet been thoroughly examined. To analyze the impact of physical activity performed by women undergoing breast cancer surgery on measures of function, range of motion, and self-efficacy. A prospective study was carried out in 157 patients who underwent surgery for BC between October 2018 and April 2019, divided into four groups according to the intensity of PA with 6 months follow-up. 50 sedentary patients and 107 active patients were enrolled; the mean age was 52.6. Women who performed physical activity, moderate to vigorous, demonstrated lower function disabilities (QuickDASH 2.22) compared with inactivity or light physical activity (QuickDASH 7.0, p < 0.001), with better shoulder flexion (159.0° vs. 150.7°, p = 0.007) and abduction (159.5° vs. 152.2°, p = 0.008). Higher PA levels, displayed in higher self-efficacy reports (9.5 vs. 8.8, p = 0.002), and return to prior job status (0.005). The PA level does not influence pain at one, three and 6 months postoperatively (p = 0.278, p = 0.304 and p = 0.304 respectively). High PA levels increase the risk of axillary web syndrome (p = 0.041), although, it reduces the incidence of chronic pain (p = 0.007). Women who practice physical activity recover better from BC surgery than sedentary women. The higher the intensity and frequency of training, the better the results. Vigorous activity cause axillary web syndrome, despite, it has a beneficial effect on lowering the rate of chronic pain.

Static mechanical allodynia in post-surgical neuropathic pain after breast cancer treatments

Objectives Static mechanical allodynia (SMA), i. e., pain caused by normally non-painful static pressure, is a prevalent manifestation of neuropathic pain (NP). Although SMA may significantly affect the patient's daily life, it is less well studied in the clinical context. We aimed to characterize SMA in women with chronic post-surgical NP (CPSNP) after breast cancer surgery. Our objective was to improve understanding of the clinical picture of this prevalent pain condition. This is a substudy of a previously published larger cohort of patients with intercostobrachial nerve injury after breast cancer surgery (Mustonen et al. Pain. 2019;160:246-56). Methods We studied SMA in 132 patients with CPSNP after breast cancer surgery. The presence, location, and intensity of SMA were assessed at clinical sensory examination. The patients gave self-reports of pain with the Brief Pain Inventory (BPI). We studied the association of SMA to type of surgery, oncological treatments, BMI, other pains, and psychological factors. General pain sensitivity was assessed by the cold pressor test. Results SMA was prevalent (84%) in this cohort whereas other forms of allodynia were scarce (6%). Moderate-to-severe SMA was frequently observed even in patients who reported mild pain in BPI. Breast and the side of chest were the most common locations of SMA. SMA was associated with breast surgery type, but not with psychological factors. Severe SMA, but not self-reported pain, was associated with lower cold pain tolerance. Conclusions SMA is prevalent in post-surgical NP after breast cancer surgery and it may represent a distinct NP phenotype. High intensities of SMA may signal the presence of central sensitization. Implications SMA should be considered when examining and treating patients with post-surgical NP after breast cancer surgery.

Sensory Changes and Postmastectomy Pain Following Preservation of Intercostobrachial Nerve in Breast Cancer Surgery: a Prospective Randomized Study

Surgery for breast cancer leads to sensory changes and persistent pain in about 20-60% of patients and is usually attributed to section of the intercostobrachial nerve (ICBN). However, the opinion is divided about the benefit of preservation of ICBN. Hence, this study was designed to assess the role of preservation of ICBN on sensory changes and acute and persistent pain following mastectomy. The study was conducted on patients undergoing modified radical mastectomy for breast cancer. At the time of surgery, ICBN was sacrificed in group I (N = 29), and preserved in group II (N = 24). Patients underwent sensory assessment for touch and pain in predefined areas after surgery. They were also assessed for acute post-operative pain and persistent pain (PP) on day 30 and 90 by numeric pain rating scale. PP was also evaluated by douleur neuropathique 4 questionnaire for assessment of its neuropathic character. Preservation of ICBN resulted in significantly better preserved sensation on lateral aspect of mastectomy incision, axilla, and medial aspect of the arm. Frequency and severity of acute post-operative pain were similar between the two groups. However, PP was significantly reduced in ICBN preserved group. At 3 months, 31% patients in group I and 12.5% in group II had clinically significant pain (p = 0.024). DN 4 assessment showed neuropathic character of pain in 20.6% and 8.33% in group I and II respectively. In our study, preservation of ICBN resulted in reduced rates of sensory loss and persistent neuropathic pain.

Sensory profiles in women with neuropathic pain after breast cancer surgery

Purpose

We performed a detailed analysis of sensory function in patients with chronic post-surgical neuropathic pain (NP) after breast cancer treatments by quantitative sensory testing (QST) with DFNS (German Research Network on Neuropathic Pain) protocol and bed side examination (BE). The nature of sensory changes in peripheral NP may reflect distinct pathophysiological backgrounds that can guide the treatment choices. NP with sensory gain (i.e., hyperesthesia, hyperalgesia, allodynia) has been shown to respond to Na⁺-channel blockers (e.g., oxcarbazepine).

Methods

104 patients with at least “probable” NP in the surgical area were included. All patients had been treated for breast cancer 4–9 years ago and the handling of the intercostobrachial nerve (ICBN) was verified by the surgeon. QST was conducted at the site of NP in the surgical or nearby area and the corresponding contralateral area. BE covered the upper body and sensory abnormalities were marked on body maps and digitalized for area calculation. The outcomes of BE and QST were compared to assess the value of QST in the sensory examination of this patient group.

Results

Loss of function in both small and large fibers was a prominent feature in QST in the area of post-surgical NP. QST profiles did not differ between spared and resected ICBN. In BE, hypoesthesia on multiple modalities was highly prevalent. The presence of sensory gain in BE was associated with more intense pain.

Conclusions

Extensive sensory loss is characteristic for chronic post-surgical NP several years after treatment for breast cancer. These patients are unlikely to respond to Na⁺-channel blockers.

Quantitative sensory profiles of upper extremity chemotherapy induced peripheral neuropathy: Are there differences in sensory profiles for neuropathic versus nociceptive pain?

Aims: The aim of this study was to define the sensory phenotypes of taxane-induced peripheral neuropathy (TIPN) between neuropathic and nonneuropathic symptoms in a breast cancer population to identify future targets for mechanism-based pain management.

Methods: Participants (n = 48) with stage I–III breast cancer. Self-report questionnaires and quantitative sensory testing were used to assess sensory symptoms. The self-report version of the Leeds Assessment for Neuropathic Symptoms and Signs (S-LANSS) divided the groups into neuropathic and nonneuropathic sensory phenotypes. In total, five visits over approximately 8 months assessed each participant from pre-chemotherapy to 6 months post-chemotherapy.

Results: Out of 191 nerve assessments, 150 had an S-LANSS <12 defined as “nonneuropathic” and 41 scored >12, which was defined as “neuropathic.” Numeric Pain Rating Scale (NPRS) was analyzed based on percentages of those experiencing 1+ pain (graded 1/10 or higher) versus no pain. The neuropathic group had 82.9% of 1+ pain vs. 28.7% in the nonneuropathic group (odds ratio = 7.49; 95% confidence interval, 2.76–20.3; P = 0.001). The neuropathic group reported impaired function on the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire (P = 0.002). Heat pain threshold resulted in statistical differences for the left hand but not the right hand in the neuropathic group (P = 0.05). No other quantitative data on warm/cool or cold or vibration demonstrated sensory differences between the groups.

Conclusions: Few differences in sensory profiles measured using quantitative sensory testing (QST) were found. Heat pain thresholds were normalized, possibly suggesting that the neuropathic group retained C-fiber and transient potential vanilloid 1 (TRPV1) function. Participants with neuropathic pain demonstrated significant differences with increased pain and decreased function.

The Prevalence, Impact, and Risk Factors for Persistent Pain After Breast Cancer Surgery in a New Zealand Population

OBJECTIVE

Few Australasian studies have assessed persistent pain after breast cancer surgery. This study aims to evaluate the prevalence, impact, and risk factors of moderate to severe persistent pain after breast cancer surgery in a New Zealand population.

METHODS

Retrospective cross-sectional study of patients who underwent breast cancer surgery between six and 48 months previously. Validated questionnaires were used to assess pain prevalence and impact, psychological distress, and upper limb function. Patients' clinical records were assessed for potential risk factors.

RESULTS

Of the 375 patients who were sent questionnaires, 201 were included in the study. More than half of the patients (N = 111, 55%) reported breast surgery related-persistent pain, with 46 (23%) rating the pain as moderate to severe. Neuropathic pain was reported by 21 (46%) patients with moderate to severe pain. Pain interference, upper limb dysfunction, and psychological distress were significantly higher in patients with moderate to severe pain (P < 0.001). Non-European ethnicity (odds ratio [OR] = 5.02, 95% confidence interval [CI] = 2.05-12.25, P < 0.001), reconstruction surgery (OR = 4.10, 95% CI = 1.30-13.00, P = 0.02), and axillary node dissection (OR = 4.33, 95% CI = 1.19-15.73, P < 0.03) were identified as risk factors for moderate to severe pain by multivariate logistic regression analysis.

CONCLUSIONS

Moderate to severe persistent pain after breast cancer surgery affects many New Zealand patients, and is associated with impaired daily life activities, physical disability, and psychological distress. Large numbers of patients undergo breast cancer surgery annually. This study emphasizes the importance of identification and management of these patients perioperatively.

What makes surgical nerve injury painful? A 4-year to 9-year follow-up of patients with intercostobrachial nerve resection in women treated for breast cancer

Nerve injury during breast cancer surgery can cause neuropathic pain (NP). It is not known why some, but not all, patients develop chronic postsurgical neuropathic pain (CPSNP) after the same nerve injury. In this study, we examined 251 breast cancer survivors with surgeon-verified intercostobrachial nerve resection to identify factors that associate with CPSNP. The patients were recruited from a previous study of 1000 women treated for breast cancer in 2006 to 2010. This enabled us to analyze preoperative factors that associate with future CPSNP. The patients were re-examined in 2014 to 2016 to diagnose CPSNP using the revised NP diagnostic criteria. Preoperative assessments were pain in the area to be operated on, any chronic pain condition, depressive symptoms, anxiety, sleep, and experimental cold pain sensitivity using the cold pressor test (CPT). Follow-up assessments were CPT, psychological factors, sleep, any chronic pain, and basic laboratory tests. One hundred thirty-seven (55%) patients with intercostobrachial nerve resection fulfilled CPSNP diagnostic criteria after 4 to 9 years. Of them, 30 patients (22%) had moderate to severe pain in self-reports and 86 (63%) presented moderate to severe evoked pain at examination. Preoperative pain in the surgical area, other chronic pains, and breast-conserving surgery were associated with future CPSNP. Other chronic pains, increased psychological burden, and insomnia, both before surgery and at the follow-up, were associated with CPSNP. Preoperative CPT did not associate with future CPSNP. Patients with established CPSNP showed increased pain sensitivity in CPT and higher levels of inflammatory markers, suggesting that central sensitization and inflammation may associate with the maintenance of CPSNP.

Palliative care: needs of advanced breast cancer patients

Advanced breast cancer is characterized by many physical manifestations with the potential to undermine the quality of life (most related to the cancer and some to treatments), as well as substantial impact on psychosocial well-being. Patients with advanced breast cancer and their families have complex needs that have to be addressed in order to minimize severe distress and deterioration in the quality of life of patients and their family members. This task requires the full engagement of an interdisciplinary approach to palliative care with strong emphasis on the assessment of needs and anticipated needs, patient expectations, skilled therapeutics, and commitment to continuity of care. In this review, we address four issues: 1) organizational and conceptual issues in palliative care of patients with breast cancer, 2) common physical symptoms among patients with breast cancer and their management, 3) common psychological issues among patients with breast cancer, and 4) common challenging palliative care problems in breast cancer.

Avoiding Catch-22: validating the PainDETECT in a in a population of patients with chronic pain

Background

Neuropathic pain is defined as pain caused by a lesion or disease of the somatosensory nervous system and is a major therapeutic challenge. Several screening tools have been developed to help physicians detect patients with neuropathic pain. These have typically been validated in populations pre-stratified for neuropathic pain, leading to a so called “Catch-22 situation:” “a problematic situation for which the only solution is denied by a circumstance inherent in the problem or by a rule”. The validity of screening tools needs to be proven in patients with pain who were not pre-stratified on basis of the target outcome: neuropathic pain or non-neuropathic pain. This study aims to assess the validity of the Dutch PainDETECT (PainDETECT_-Dlv) in a large population of patients with chronic pain.

Methods

A cross-sectional multicentre design was used to assess PainDETECT_-Dlv validity. Included where patients with low back pain radiating into the leg(s), patients with neck-shoulder-arm pain and patients with pain due to a suspected peripheral nerve damage. Patients’ pain was classified as having a neuropathic pain component (yes/no) by two experienced physicians (“gold standard”). Physician opinion based on the Grading System was a secondary comparison.

Results

In total, 291 patients were included. Primary analysis was done on patients where both physicians agreed upon the pain classification (n = 228). Compared to the physician’s classification, PainDETECT_-Dlv had a sensitivity of 80% and specificity of 55%, versus the Grading System it achieved 74 and 46%.

Conclusion

Despite its internal consistency and test-retest reliability the PainDETECT_-Dlv is not an effective screening tool for a neuropathic pain component in a population of patients with chronic pain because of its moderate sensitivity and low specificity. Moreover, the indiscriminate use of the PainDETECT_-Dlv as a surrogate for clinical assessment should be avoided in daily clinical practice as well as in (clinical-) research. Catch-22 situations in the validation of screening tools can be prevented by not pre-stratifying the patients on basis of the target outcome before inclusion in a validation study for screening instruments.

Trial registration

The protocol was registered prospectively in the Dutch National Trial Register: NTR 3030.

Electronic supplementary material

The online version of this article (10.1186/s12883-018-1094-4) contains supplementary material, which is available to authorized users.

Pain medicine content, teaching and assessment in medical school curricula in Australia and New Zealand

BACKGROUND

The objective of pain medicine education is to provide medical students with opportunities to develop their knowledge, skills and professional attitudes that will lead to their becoming safe, capable, and compassionate medical practitioners who are able to meet the healthcare needs of persons in pain. This study was undertaken to identify and describe the delivery of pain medicine education at medical schools in Australia and New Zealand.

METHOD

All 23 medical schools in Australia and New Zealand in 2016 were included in this study. A structured curriculum audit tool was used to obtain information on pain medicine curricula including content, delivery, teaching and assessment methods.

RESULTS

Nineteen medical schools (83%) completed the curriculum audit. Neurophysiology, clinical assessment, analgesia use and multidimensional aspects of pain medicine were covered by most medical schools. Specific learning objectives for pain medicine were not identified by 42% of medical schools. One medical school offered a dedicated pain medicine module delivered over 1 week. Pain medicine teaching was delivered at all schools by a number of different departments throughout the curriculum. Interprofessional learning (IPL) in the context of pain medicine education was not specified by any of the medical schools. The mean time allocated for pain medicine teaching over the entire medical course was just under 20 h. The objective structured clinical examination (OSCE) was used by 32% of schools to assess knowledge and skills in pain medicine. 16% of schools were unsure of whether any assessment of pain medicine education took place.

CONCLUSION

This descriptive study provides important baseline information for pain medicine education at medical schools in Australia and New Zealand. Medical schools do not have well-documented or comprehensive pain curricula that are delivered and assessed using pedagogically-sound approaches considering the complexity of the topic, the prevalence and public health burden of pain.