Cancer Pain (PDQ®)–Health Professional Version

General Information About Cancer Pain

Pain is one of the most common symptoms in cancer patients and often has a negative impact on patients’ functional status and quality of life (QOL). The goal of the following summary is to provide evidence-based, up-to-date, and practical information on the management of cancer pain.

Effective pain management can generally be accomplished by paying attention to the following steps:[1]

Regular screening to ensure that the patient’s pain is recognized early. (Refer to the Pain Assessment section of this summary for more information.)
Proper characterization of the pain to identify underlying pathophysiology, which could significantly influence treatment options. (Refer to the Pain Classification section of this summary for more information).
- Is the pain acute or chronic?
- Is it secondary to cancer, cancer treatment, other causes, or a combination?
- Is it somatic, visceral, neuropathic, or mixed?
- Is there an incidental component?
- Is there breakthrough pain?
Determining whether the pain requires pharmacologic and/or other modalities of treatment. Pain is often multifactorial in nature, so factors that may modulate pain expression, such as psychological distress and substance use, should be assessed. (Refer to the Background and Definitions section of this summary for more information.)
- What is the impact of pain on the patient?
- Is the benefit of treatment likely going to outweigh the risks?
Identifying the optimal pharmacologic and nonpharmacologic treatment options (refer to the Pharmacologic Therapies for Pain Control section of this summary for more information), including referrals to specialists, if needed. (Refer to the Modalities for Pain Control: Other Approaches section of this summary for more information.) Complex pain often requires multidimensional interdisciplinary evaluation and intervention. There are many issues to consider when determining the most appropriate treatment, such as the following:
- Previous pain treatments.
- Patient prognosis.
- Predictive factors for pain control (e.g., psychological distress).
- Impact on function.
- Comorbidities (e.g., renal or hepatic failure).
- Risk of misuse of or addiction to pain medications.
- Patient preference.
Providing proper education about treatment, including medication administration, expected side effects and associated treatments, and when patients can expect improvement. If opioids are considered, fear of opioids and the risks of opioid use and misuse should be addressed. Patients and family caregivers should be educated about the safe storage, use, and disposal of opioids. One study demonstrated that improper use, storage, and disposal are common among cancer outpatients.[2]
Monitoring the patient longitudinally with return visits to titrate/adjust treatments. Patients with cancer or noncancer pain requiring chronic therapy are monitored closely to optimize treatment and to minimize the likelihood of complications of opioid use, including misuse or abuse. The risks and benefits of opioid use are evaluated regularly, and physician impressions are discussed openly with the patient.

Background and Definitions

The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”[3] Pain is commonly experienced by cancer patients. Its proper assessment requires the following:

Measuring pain intensity.
Clarifying the impact of pain on patients’ psychological, social, spiritual, and existential domains.
Establishing treatment adherence and responsiveness.

A commonly used approach to pain management employs the three-step World Health Organization (WHO) pain relief ladder , which categorizes pain intensity according to severity and recommends analgesic agents based on their strength.[4] Pain intensity is often assessed using a numeric rating scale (NRS) of 0 to 10. On this scale, 0 indicates no pain, 1 to 3 indicates mild pain, 4 to 6 indicates moderate pain, and 7 to 10 indicates severe pain.[5]

Following is a summary of the three steps in the WHO cancer pain ladder for adults:

Step 1 treats mild pain. Patients in this category receive nonopioid analgesics such as acetaminophen, nonsteroidal anti-inflammatory drugs, or an adjuvant analgesic, if necessary.
Step 2 treats patients experiencing mild to moderate pain who are already taking a nonopioid analgesic, with or without an adjuvant analgesic, but who are still experiencing poor analgesia. Step 2 agents include tramadol and acetaminophen products containing hydrocodone, oxycodone, and codeine.
Step 3 treats moderate to severe pain with strong analgesics. Step 3 opioids include morphine, hydromorphone, fentanyl, levorphanol, methadone, oxymorphone, and oxycodone.

The results of an open-label randomized trial of low-dose morphine versus weak opioids to treat moderate cancer pain suggested that it is acceptable to bypass weak opioids and go directly to strong opioids (step 3 agents) for patients with moderate cancer pain, as patients randomly assigned to the low-dose morphine group had more frequent and greater reduction in pain intensity with similarly good tolerability and earlier effect.[6]

Familiarity with opioid pharmacokinetics, equianalgesic dosing, and adverse effects is necessary for their safe and effective use. The appropriate use of adjuvant pharmacological and nonpharmacological interventions is needed to optimize pain management.

Prevalence

Pain occurs in 20% to 50% of patients with cancer.[7] Roughly 80% of patients with advanced-stage cancer have moderate to severe pain.[8] One meta-analysis looking at pooled data from 52 studies found that more than half of patients had pain.[9] Younger patients are more likely to experience cancer pain and pain flares than are older patients.[10]

Causes of Cancer Pain: Cancer, Cancer Treatments, and Comorbidities

A study evaluating the characteristics of patients (N = 100) with advanced cancer presenting to a palliative care service found the primary tumor as the chief cause of pain in 68% of patients.[11] Most pain was somatic, and pain was as likely to be continuous as intermittent.

Pain can be caused by the following cancer therapies:

Surgery.
Radiation therapy.
Chemotherapy.
Targeted therapy.
Supportive care therapies.
Diagnostic procedures.

A systematic review of the literature identified reports of pain occurring in 59% of patients receiving anticancer treatment and in 33% of patients after curative treatments.[9] The prevalence of chronic nonmalignant pain—such as chronic low back pain, osteoarthritis pain, fibromyalgia, and chronic daily headaches—has not been well characterized in cancer patients. It has been reported to range from 2% to 76%, depending on the patient population and how pain was assessed.[12-15]