What are the treatment options for chronic cancer pain?

Treatment Options for Chronic Cancer Pain

Chronic cancer pain should be managed using the WHO analgesic ladder with stepwise escalation from non-opioids to weak opioids to strong opioids based on pain severity, combined with adjuvant medications and non-pharmacological interventions as needed. 1

Initial Assessment and Screening

• Screen for pain at every clinical encounter using quantitative tools (e.g., visual analogue scales or numerical rating scales) 1
• Conduct comprehensive pain assessment including pain descriptors, functional impact, cancer treatment history, and psychosocial factors 1
• Evaluate for recurrent disease, second malignancy, or late-onset treatment effects in patients with new-onset pain 1
• Pain should be managed during the diagnostic evaluation, not delayed until diagnosis is complete 1

Pharmacological Management: The WHO Analgesic Ladder

Step 1: Mild Pain (NRS ≤4)

Non-opioid analgesics are first-line for mild pain:

• Acetaminophen/Paracetamol: 650 mg every 4-6 hours (maximum 4 g/day) 1
• NSAIDs: Effective for inflammatory pain, particularly bone pain 1
  • No single NSAID has proven superior efficacy over others 1
  • Use with caution in patients receiving nephrotoxic chemotherapy (especially cisplatin) or with bleeding risk 1
  • Consider COX-2 inhibitors for patients with gastric intolerance, though evidence for cancer pain is limited 1

Step 2: Moderate Pain (NRS 5-6)

Weak opioids combined with non-opioid analgesics:

• Codeine, tramadol, or dihydrocodeine in combination with acetaminophen or NSAIDs 1
• Alternative approach: Low-dose strong opioids (e.g., morphine) may be used instead of weak opioids, especially when progressive pain is expected 1
  • The evidence for Step 2 efficacy is limited, with effectiveness typically lasting only 30-40 days 1
  • Many experts advocate for early use of low-dose morphine rather than weak opioids 1

Important caveat: Do not combine weak opioids with strong opioids 1

Step 3: Severe Pain (NRS ≥7)

Strong opioids are the mainstay for moderate-to-severe cancer pain:

• Oral morphine is the first-choice strong opioid 1

  • Oral route is preferred when possible 1
  • Parenteral (IV/SC) to oral morphine ratio is 1:2 to 1:3 1
  • Provide around-the-clock dosing with immediate-release "breakthrough" doses (10% of total daily dose) 1
  • If >4 breakthrough doses needed daily, increase baseline long-acting formulation 1

• Alternative strong opioids (when morphine is not tolerated or contraindicated):

  • Hydromorphone or oxycodone (immediate-release and modified-release formulations) 1
  • Methadone (more complex dosing due to variable half-life) 1
  • Transdermal fentanyl: Reserved for patients with stable opioid requirements ≥60 mg/day oral morphine equivalent 1, 2
  • Transdermal buprenorphine: Useful for patients with renal impairment 1

• Strong opioids can be combined with Step 1 non-opioids for additive effect 1

Adjuvant Analgesics (Can Be Added at Any Step)

For neuropathic pain or specific pain syndromes:

• Antidepressants: Duloxetine has evidence for neuropathic pain 1
• Anticonvulsants: Gabapentin and pregabalin for neuropathic pain conditions 1
• Corticosteroids: Specific role in spinal cord compression and brain metastases 3
• Bisphosphonates or denosumab: For bone metastases pain 3

Non-Pharmacological Interventions

Consider referral for interventional procedures when:

• Pain is likely to be relieved with nerve blocks (celiac plexus block for upper abdominal pain, superior hypogastric plexus block for pelvic pain) 1
• Failure to achieve adequate analgesia without intolerable side effects 1
• Specific procedures include: percutaneous vertebroplasty/kyphoplasty, radiofrequency ablation for bone lesions, neurodestructive procedures, or spinal cord stimulation 1

Other modalities to consider:

• Physical therapy, cognitive-behavioral interventions, psychological support, and rehabilitative interventions 1
• Spiritual care when important to patient/family 1

Opioid Management: Critical Safety Considerations

For cancer survivors on chronic opioids:

• Prescribe opioids only in carefully selected patients who do not respond to conservative management and continue to experience distress or functional impairment 1
• Assess risks of adverse effects including tolerance, dependence, abuse, and addiction 1
• Incorporate universal precautions to minimize abuse and diversion 1
• When tapering opioids, reduce by no more than 10-25% of total daily dose every 2-4 weeks to avoid withdrawal 4
• Ensure multimodal pain management approach is in place before initiating taper 4

Common Pitfalls to Avoid

• Do not delay pain management until diagnostic workup is complete 1
• Do not combine drugs from the same opioid class with similar kinetics (e.g., two sustained-release opioids) 1
• Do not mix weak and strong opioids simultaneously 1
• Always anticipate and prophylactically treat constipation in patients receiving opioids 1
• Do not use transdermal fentanyl in opioid-naïve patients or those with unstable pain 1
• Monitor for acetaminophen toxicity when combining with opioid-acetaminophen products 1

Multidisciplinary Approach

Determine need for specialty consultation:

• Pain management specialists for complex cases or interventional procedures 1
• Substance abuse consultation if concerns about medication misuse or diversion 1
• Comprehensive team approach for patients with complex needs 1