Some 90% of patients with cancer experience pain during their illness.1 The pain usually worsens as the disease progresses, and patients may experience different types of pain.
Persistent pain decreases function, appetite, and sleep, induces fear, causes depression, and generally lowers the quality of life.2 Persistent pain is demoralizing and debilitating for patients and their caregivers.3
Adequate pain control is important to ensure that patients can function productively, maintain social relationships, and improve their quality of life.2 Yet 86% of practicing physicians surveyed believed that most cancer patients with pain were undermedicated,2 and most felt that pain management is unsuccessful in more than half of patients who seek help.3
The critical importance of pain management has been emphasized by the World Health Organization (WHO), by international and national professional organizations, and by government agencies. All practitioners who care for cancer patients need to be well educated in managing cancer pain, a key part of which is to educate patients about the process and what to expect. This results in better pain control.4
Although much has been written on the management of cancer pain in a referral setting, little has been published on how to manage it in primary care. In this article, we discuss common questions faced by generalists. We emphasize the use of opioids, perhaps the most challenging aspect of cancer pain management. We also discuss when consultation with a specialist in pain management or a palliative medicine specialist is especially helpful.
WHAT ARE THE DIFFERENT TYPES OF PAIN SYNDROMES?
Pain is classified in several ways1–6:
Nociceptive vs neuropathic. Nociceptive pain comprises somatic and visceral components and is the result of continued tissue injury.4 Neuropathic pain is due to injury to the peripheral and central nervous systems and occurs within an area of sensory or motor deficit.
Continuous vs intermittent. Continuous pain, even if controlled, can have breakthroughs, ie, flares of pain above the controlled baseline level. Intermittent pain is a pain flare without chronic baseline pain. Intermittent pain is further divided into incident pain (ie, on movement) and end-of-dose failure (ie, pain occurring just before the next scheduled opioid dose).5 Pain specialists continue to debate the meaning and the use of these terms.
Malignant vs nonmalignant. Cancer pain is multifactorial,1 being induced by the disease itself, by the treatment of cancer, and by pain unrelated to cancer or its treatment (eg, osteoarthritis or diabetic neuropathy).2
Familiarity with the causes and the types of pain, including pain related to cancer, is important, as this influences treatment decisions.
HOW IS PAIN ASSESSED?
The assessment of pain is vital in managing it.
Since pain is inherently subjective, the patient’s self-report is the gold standard.4 Characteristics of the pain along with a physical examination, laboratory testing, and imaging studies can define the pathophysiology of the pain and influence the decision to undertake further assessment or specific therapies.
Patients and physicians can use various scales, such as a visual analog scale, a numerical rating scale, a graphic scale, a verbal scale, a word descriptor scale, and a functional pain scale. A verbal scale can be used if the patient is alert, or a nonverbal scale if the patient has impaired cognition or speaks a different language. Intensity is the most common dimension evaluated in cancer pain, primarily via a numerical or visual analog scale. A numerical scale score of 0 to 10 has been found to be as effective as a visual analog scale (0 to 100 mm),7,8 and the numerical rating scale is generally preferred as a measure of pain intensity.9
There are no clear guidelines for selecting one scale over another.7 A clinically meaningful response (ie, meaningful to patients) is at least a two-point decrease on the 10-point numerical scale or a 13-mm decrease on the 100-mm visual analog scale. A decrease in the percentage of the pain relates to global improvement better than an absolute reduction on the numerical scale.
WHAT PROBLEMS ARE ENCOUNTERED IN MANAGING CANCER PAIN?
WHAT ARE THE DIFFERENT WAYS TO MANAGE CANCER PAIN?
Pain should be treated promptly and aggressively, because if untreated it can lead to delays in healing, changes in the central nervous system (eg, sensitization, plasticity), chronic stress, family stress, depression, job loss, and even suicide.12–14
Comprehensive pain management improves outcomes and includes the rational use of opioids and adjuvant analgesics, physical rehabilitation, cognitive behavioral (non-drug) therapies, family counseling, interventional procedures (kyphoplasty, nerve blocks, local injections, spinal analgesia), and complementary therapies such as acupuncture.12 Adjuvant analgesics include antidepressants, anticonvulsants, and local anesthetics.