Failure to assess pain is a critical factor leading to undertreatment. Assessment involves both the clinician and the patient. Assessment should occur at the following times:
- At each clinical encounter.
- At regular intervals after initiation of treatment.
- At each new report of pain.
- At a suitable interval after pharmacologic or nonpharmacologic intervention (e.g., 15–30 minutes after parenteral drug therapy and 1 hour after oral administration).
Effective pain management requires close monitoring of patient response to initiation of treatment. In a review of 1,612 patients referred to an outpatient palliative care center where patients with advanced cancer were seen by both a palliative care nurse and a physician, more than half of patients with moderate to severe pain did not respond to an initial palliative care consultation, with response defined as a two-point or more reduction or a 30% or more reduction from baseline. Also, one-third of patients with mild pain actually progressed to moderate to severe pain by the time of their first follow-up visit. The authors concluded that more frequent follow-up visits, calls, and interdisciplinary clinics should be considered in an effort to optimize pain control. The study also identified baseline pain intensity, fatigue, and Edmonton Symptom Assessment System symptom burden as factors predicting response.[Level of evidence: III]
Identifying the etiology of pain is important to its management. Clinicians treating patients with cancer should recognize the common cancer pain syndromes (see lists below). Prompt diagnosis and treatment of these syndromes can reduce morbidity associated with unrelieved pain. Distinct cultural components may need to be incorporated into a multidimensional assessment of pain.[2-5] Reviews of cancer pain with a focus on neuropathic pain describes pathophysiologies as well as available and investigational pharmacotherapies.[6,7][Level of evidence: II]
Common Pain Syndromes: Pain Associated with Tumor
- Bone marrow expansion
- Vertebral syndrome
- Local infiltration
- Base of skull involvement
- Hepatic capsule distension
- Retroperitoneal syndrome
- Intestinal obstruction
- Ureteral obstruction
- Cranial neuropathies
- Leptomeningeal disease
- Base of skull metastases
- Brachial, cervical, sacral
- Cauda equina syndrome
- Cranial neuropathies
- Sensorimotor neuropathy
Common Pain Syndromes: Pain Secondary to Treatment
- Radiation fibrosis
- Brachial, sacral
- Pain flare after radiopharmaceutical
- Radiation-induced cystitis
- Arthralgia, myalgia
- Aromatase inhibitors
- Avascular necrosis
- Chronic abdominal pain
- Platinum-based products: Cisplatin, carboplatin, oxaliplatin
- Taxanes: Paclitaxel, docetaxel
- Vinca alkaloids: Vincristine, vinblastine
- Epothilones: Ixabepilone
- Others: Bortezomib, lenalidomide, thalidomide
- Arthralgia, myalgia
- Bone pain flare
- Arthralgia, myalgia
- Acute postoperative or procedural pain
- Phantom limb pain/postamputation pain
- Postnephrectomy syndrome
- Postmastectomy syndrome
- Postthoracotomy syndrome
- Post–radical neck dissection
- Pelvic floor myalgia
- Bone pain, osteonecrosis
The goal of the initial assessment of pain is to characterize the pathophysiology of the pain and to determine the intensity of the pain and its impact on the patient’s ability to function. For example, one study evaluated the association between psychological distress and pain in 120 patients with advanced cancer. Pain intensity and pain that interfered with walking ability, normal work, and relations with other people, as measured by the Brief Pain Inventory (Greek version), were found to be significant predictors of anxiety, as measured by the Hospital Anxiety and Depression Scale on multivariate analysis. Using the same tools, the authors also found pain that interfered with enjoyment of life was a predictor of depression.[Level of evidence: II] Factors that may influence analgesic response and result in persistent pain include changing nociception due to disease progression, intractable side effects, tolerance, neuropathic pain, and opioid metabolites.[Level of evidence: IV] The following are essential to the initial assessment:
The experience of cancer pain is complex and includes physical, psychosocial, and spiritual dimensions. There is no universally accepted pain classification measure that assists with predicting the complexity of pain management, particularly for cancer pain patients, who may be more difficult to treat. Clinicians and researchers lack a common language to discuss and compare outcomes of cancer pain assessment and management. Oncologists use the tumor, nodes, metastases (TNM) system as a universal language to describe a variety of cancers. The need for a similar classification system for cancer pain resulted in the development of the Edmonton Staging System.[11,12] This system has been further refined in two reports that have gathered construct validity evidence using an international panel of content experts  and a multicenter study to determine interrater reliability and predictive value. The development of an internationally recognized classification system for cancer pain could play a significant role in improving the assessment of cancer pain, allow a more meaningful assessment of clinical prognosis and treatment, and better enable researchers to compare results with regard to cancer pain management.[Level of evidence: II]
The mainstay of pain assessment is the patient self-report; however, family caregivers are often used as proxies for patient reports, especially in situations in which communication barriers exist, such as cognitive impairment or language difficulties. Family members who act as proxies typically, as a group, report higher levels of pain than patient self-reports, but there is individual variation.[16,17][Level of evidence: II] Differences in clinician assessment of pain intensity are also significant. A retrospective review of 41 patient charts using pain ratings of palliative care consultants as the gold standard found high agreement with assessments performed by bedside nurses (registered nurses [RNs] and clinical nurse assistants [CNAs]) when pain was not present or was mild but poor agreement for moderate or severe pain (sensitivity: RNs, 45%; CNAs, 30%).[Level of evidence: III]
Pain assessment tools may be unidimensional or multidimensional. Multiple assessment tools exist. Among the more commonly used bedside tools are numeric rating scales, verbal rating scales, visual analog scales, and picture scales.[19,20][Level of evidence: IV] Pain intensity at initial assessment has been demonstrated to be a significant predictor of subsequent pain management complexity (i.e., the need for more pharmacological and multidimensional approaches) and length of time to achieve stable pain control.[Level of evidence: II] To enhance pain management across all settings, clinicians should teach families to use pain assessment tools in their homes. The clinician should help the patient to describe:
- Listen to the patient’s descriptive words about the quality of the pain; these provide valuable clues to its etiology. Elicit the temporal features including onset, duration, and diurnal variation. Ask about breakthrough pain (BP) or episodic pain (EP) (a transitory increase in pain that occurs in addition to persistent pain). Some patients may have EP without persistent pain.[Level of evidence: IV] The prevalence of BP-EP varies widely, depending on which definition is used and based on the clinical scenario and cultural setting. An appropriately designed, cross-sectional, multicenter study that evaluated BP-EP in patients with chronic cancer-related pain was completed. The primary aim of the study was to assess the prevalence and characteristics of BP-EP on the basis of clinical assessment and through the use of a previously validated, culturally adapted tool, the Questionnaire for Intense Episodic Pain (QUDEI-Italian), which utilizes a patient interview technique. Physicians who participated in the study were trained to define and recognize BP-EP. Patient evaluation and use of the questionnaire were carried out by different sets of providers. There was an estimated prevalence of 73% when a BP-EP diagnosis was made by physicians and 66% when the QUDEI was applied. When patients with baseline pain levels of 6 or lower (based on a numerical rating scale from 0 to 10) were analyzed, the physician prevalence decreased to 67%, versus 60% with tool utilization. The authors concluded that because of the frequent occurrence of BP-EP, a more widely accepted general definition of this phenomenon and specific validated tools to assist in education and screening are needed.
- Ask the patient to indicate the exact location of the pain on his or her body, or on a body diagram, and whether the pain radiates.
Changes in Pattern
- Changes in pain pattern or the development of new pain should trigger diagnostic reevaluation and modification of the treatment plan. Persistent pain indicates the need to consider other etiologies (e.g., related to disease progression or treatment) and alternative (perhaps more invasive) treatments.
Intensity or Severity
- Encourage the patient to keep a log of pain-intensity scores to report during follow-up visits or by telephone. Examples of simple self-report pain-intensity scales include the simple, descriptive, numeric, and visual analog scales.
Aggravating and Relieving Factors
- Ask the patient to identify factors that cause the most pain and also what relieves the pain.
Cognitive Response to Pain
- Cognitive appraisals of pain can be based on a range of psychological variables such as perceived control, meaning attributed to pain experience, fear of death, and hopelessness. All these variables appear to contribute to the experience of cancer pain and suffering. A study of women with metastatic breast cancer found that although the site of metastasis did not predict the intensity of pain report, greater depression and the belief that pain represented the spread of disease significantly predicted the degree of pain experienced. It was also reported that patients who thought that their pain represented disease progression reported more pain-related interference with function.[Level of evidence: II]
- Note behavior that suggests pain in patients who are cognitively impaired or who have communication problems relating to education, language, ethnicity, or culture. Cognitive impairment itself and the degree of cognitive impairment may impact patient self-report of pain. Preliminary data suggest that mild degrees of cognitive impairment are associated with increased intensity of pain-report in older patients with cancer who are receiving hospice care. In contrast, cognitively impaired nursing home residents are less likely to report pain. Use appropriate (e.g., simpler or translated) pain assessment tools.
Goals for Pain Control
- Document the patient’s preferred pain assessment tool and the goals for pain control (such as scores on a pain scale).
- Encourage use of the pain diary: The daily pain diary is a well-established tool in symptom management research and in clinical practice. Benefits of using a pain diary include heightened awareness of pain, guidance for pain management behaviors, enhanced sense of control, and a tool for communication. It is difficult to get good pain-diary compliance with adolescents who are experiencing intense chronic pain.
A thorough physical examination is required to determine the pathophysiology of pain. Specific features of the neurologic examination such as altered sensation (hypoesthesia, hyperesthesia, hyperpathia, allodynia) in a painful area are suggestive of neuropathic pain. Physical findings of tumor growth and metastasis are also important to identify.
Information obtained from the synthesis of history, physical examination, and diagnostic evaluations is used to generate a pain diagnosis with respect to etiology (cancer, its treatment, or other) and pathophysiology (somatic, visceral, and/or neuropathic). This diagnosis, in conjunction with contributing psychosocial and spiritual factors, is used to generate a comprehensive pain treatment plan.
Assessment of the Outcomes of Pain Management
Pain-related outcomes: Clinicians should document and be aware of outcomes of pain therapy. It is helpful to think of pain-related outcomes as primarily measured in two ways: decreased pain intensity and improvement in psychosocial functioning. Using rating scales of pain intensity at its worst and on average and using pain interference scales can help clinicians monitor outcomes. Measurement of the percentage of pain relief is also useful, though measuring patient satisfaction is less useful because of the low expectations patients sometimes hold for pain control.[28,29]
Drug-taking outcomes: Clinicians prescribing chronic opioids should also monitor and document patients’ drug-taking behaviors. Outcomes related to addiction in cancer patients are rare but nonetheless should be periodically assessed; these assessments can be reassuring to patients. Tolerance and dependence are not addiction related. Documentation of patients’ compliance with regard to changes in dosing and duration of prescriptions is essential in all pain practice.
The clinical assessment of drug-taking behaviors in medically ill patients with pain is complex. Aberrant drug-taking behavior from cancer pain management is related to premorbid history of drug addiction and the likelihood of other pain treatment. A pilot questionnaire was used to characterize drug-related behaviors and attitudes in cancer and AIDS patients. Despite limitations, this study highlights wide potential variation among different palliative care populations in patterns of past and present aberrant drug-taking behaviors and the need for a clinically useful screening approach. The implications for psychosocial and pharmacological management of symptoms such as pain, as well as any aberrant behavior, remain unclear.[30-32]
Previous drug abuse is likely to lead to specific needs for appropriate dosing during cancer pain therapy. A prospective open-label study compared morphine dosage and effectiveness in AIDS patients with and without previous substance abuse. Results demonstrated that both groups benefited, but patients with a history of drug use required and tolerated substantially higher morphine doses to achieve stable pain control.[Level of evidence: II] This study should increase confidence in providing appropriate pain management to patients who have a history of drug use.[Level of evidence: IV]
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