What are the treatment options for cancer pain management?

Cancer Pain Management

The most effective approach to cancer pain management is following the WHO analgesic ladder, starting with non-opioids for mild pain, adding weak opioids for moderate pain, and using strong opioids like morphine for severe pain, with around-the-clock dosing and breakthrough doses. 1, 2

Pain Assessment

• All cancer patients should be evaluated for pain at every clinical visit using standardized self-reporting tools such as visual analog scales (VAS), numerical rating scales (NRS), or verbal rating scales (VRS) 1
• Pain assessment should characterize the type (nociceptive, neuropathic), location, intensity, duration, and temporal patterns 1
• Over 80% of cancer patients with advanced metastatic disease experience pain, primarily from direct tumor infiltration, while approximately 20% of pain may be attributed to effects of surgery, radiotherapy, or chemotherapy 3

Pharmacological Management Based on Pain Intensity

Mild Pain (WHO Level I)

• Use non-opioid analgesics such as acetaminophen/paracetamol (maximum 4000 mg/day) or NSAIDs 3, 1
• When using NSAIDs over a prolonged period, provide gastroprotection to prevent GI toxicity 1
• Consider selective COX-2 inhibitors for patients with gastric intolerance of other NSAIDs, though there are unsettled toxicity issues 3

Moderate Pain (WHO Level II)

• Add weak opioids (codeine, dihydrocodeine, tramadol) to non-opioid analgesics 3, 1
• Low doses of morphine or its equivalents are a reasonable alternative, especially if progressive pain is anticipated 3
• Weak opioids may be combined with ongoing use of a non-steroidal anti-inflammatory agent but not with WHO level III analgesics 3

Severe Pain (WHO Level III)

• Use strong opioids such as morphine (preferred first-line), hydromorphone, oxycodone, or fentanyl 3, 1
• Oral administration is preferred when possible; if given parenterally, the equivalent dose is 1/3 of the oral medication 3
• Transdermal fentanyl is best reserved for patients whose opioid requirements are stable at a level corresponding to ≥ 60 mg/day of morphine 3, 4

Principles of Opioid Administration

• Provide around-the-clock dosing for persistent pain rather than "as needed" administration 1
• Include "breakthrough" doses (typically 10-15% of total daily dose) for transient pain exacerbations 3, 1
• Titrate doses rapidly to achieve effective pain control, and adjust the baseline opioid regimen if more than four breakthrough doses are needed daily 3, 1
• When converting between opioids, use established equianalgesic dose tables to ensure appropriate dosing 4

Management of Opioid Side Effects

• Anticipate and proactively manage common side effects, including constipation, nausea/vomiting, and central nervous system toxicity 3, 1
• Use prophylactic laxatives for constipation, antiemetics for nausea, and consider dose reduction or opioid rotation for persistent side effects 1
• In some cases, reduction in opioid dose may alleviate refractory side effects, which may be achieved by using adjuvant analgesics 3
• Monitor for drug interactions, particularly when using fentanyl with CYP3A4 inhibitors, which can increase fentanyl plasma concentrations and potentially cause fatal respiratory depression 4

Adjuvant Analgesics for Specific Pain Types

• Consider anticonvulsants (gabapentin, pregabalin), antidepressants (tricyclics, SNRIs), or corticosteroids for neuropathic pain 1, 2
• Use bone-modifying agents (bisphosphonates, denosumab) for bone pain 1, 2
• Adjuvant analgesics play an important role in the treatment of cancer pain not fully responsive to opioids administered alone 5

Non-Pharmacological and Interventional Approaches

• Consider radiation therapy for localized bone pain 1, 2
• Evaluate surgical stabilization for impending fractures 2
• Consider nerve blocks for specific pain syndromes when pain is inadequately controlled despite optimal pharmacologic therapy 1, 6
• Interventional strategies include regional infusion of analgesics, nerve blocks, and vertebral augmentation 1

Special Considerations

• For elderly or debilitated patients, use caution as they may have altered pharmacokinetics due to poor fat stores, muscle wasting, or altered clearance 4
• In pediatric patients over 2 years of age with chronic pain, ensure they are opioid-tolerant before initiating strong opioids 4
• Cancer pain remains inadequately controlled despite available therapies, making it essential for all practitioners to prioritize pain control 7

Common Pitfalls to Avoid

• Underestimating pain severity, particularly in patients with cognitive impairment 2
• Failing to recognize that most cancer patients have multiple types of cancer-related pain 2
• Inadequate titration of opioids leading to poor pain control 2
• Not addressing concerns about opioid use in patients and families 2
• Neglecting to provide prophylactic management of opioid side effects 2