Cancer Pain Management

Cancer Pain Fundamentals - The Painful Truth

• Prevalence: Affects 50-80% of cancer patients, severely impacting Quality of Life (QoL).
• Etiology: Tumor invasion/compression, treatment side-effects (chemo, radio, surgery), paraneoplastic syndromes.
• Types: Nociceptive (somatic, visceral), neuropathic; often mixed.
• Assessment: Crucial. Use PQRST mnemonic (📌). Scales: Numeric Rating Scale (NRS 0-10), Visual Analog Scale (VAS), Brief Pain Inventory (BPI).

  ⭐ The WHO three-step analgesic ladder is a cornerstone of cancer pain management, guiding stepwise opioid and adjuvant use. oka

WHO Ladder & Basics - Stepping Up Relief

WHO 3-step ladder: Key principles are "By the mouth", "By the clock", "By the ladder", and individualized therapy.

• Step 1 (Mild Pain): Non-opioid (e.g., Paracetamol, NSAID) ± Adjuvant.
• Step 2 (Moderate Pain): Weak opioid (e.g., Tramadol, Codeine) ± Non-opioid ± Adjuvant.
• Step 3 (Severe Pain): Strong opioid (e.g., Morphine, Fentanyl) ± Non-opioid ± Adjuvant.
  • Adjuvants (e.g., Gabapentinoids, TCAs) for specific pain types.

⭐ Prophylactic laxatives (e.g., senna + docusate) should be prescribed with opioids to prevent constipation.

Opioid Arsenal - Potent Painkillers

• Morphine: Gold standard (PO, IV, SC).
  • M6G (active metabolite, renal excretion).
  • SE: Nausea, constipation, sedation, resp. depression.
• Fentanyl: Potent (80-100x morphine).
  • Patch (stable chronic pain), transmucosal (BTcP).
  • Safer in renal failure.
• Methadone: Long, variable T½. Mu-agonist, NMDA antagonist (neuropathic pain).
  • ⚠️ QT prolongation risk; careful titration.
• Tapentadol: Mu-agonist & NRI (Norepinephrine Reuptake Inhibitor).
  • ↓ constipation compared to other opioids.
• Buprenorphine: Partial mu-agonist.
  • Ceiling effect on respiratory depression.
  • Sublingual, transdermal routes.
• Tramadol: Weak mu-agonist, SNRI.
  • Max dose 400mg/day.
  • Seizure risk; serotonin syndrome risk.

⭐ M6G (morphine's active metabolite) accumulates in renal failure; consider dose ↓ or switch opioid (e.g., to fentanyl or methadone).

Adjuvants & Co-analgesics - Helper Meds

• Purpose: Enhance opioid efficacy, manage specific pain types (neuropathic, bone), reduce opioid side effects.
• Neuropathic Pain:
  • Antidepressants: Amitriptyline (10-25 mg HS), Duloxetine (30-60 mg OD).
  • Anticonvulsants: Gabapentin (start 100-300 mg), Pregabalin (start 25-75 mg).
• Bone Pain:
  • NSAIDs (use cautiously).
  • Corticosteroids: Dexamethasone (4-8 mg BD) for inflammation, nerve compression.
  • Bisphosphonates (e.g., Zoledronic acid), Denosumab.
• Other Key Adjuvants:
  • Ketamine (low dose): Refractory neuropathic pain, opioid-induced hyperalgesia.

⭐ For neuropathic cancer pain, gabapentinoids (Gabapentin, Pregabalin) and TCAs (Amitriptyline) are often first-line adjuvants.

Interventional Strategies - Beyond Pills

• Neurolytic Blocks: Chemical (alcohol) or thermal ablation.
  • Celiac plexus (pancreatic, upper GI cancer).
  • Superior hypogastric plexus (pelvic pain).
  • Ganglion Impar (perineal, coccygeal pain).
• Intrathecal Drug Delivery (IDDS): Refractory pain; opioids, ziconotide.
• Spinal Cord Stimulation (SCS): Neuropathic pain.
• Vertebroplasty/Kyphoplasty: Painful vertebral fractures.
• Cordotomy: For intractable unilateral somatic pain.

⭐ Celiac plexus neurolysis offers significant pain relief for 60-90% of patients with pancreatic cancer pain.

High‑Yield Points - ⚡ Biggest Takeaways

• The WHO analgesic ladder (non-opioid → weak opioid → strong opioid) is fundamental for cancer pain management.
• Opioids (e.g., morphine, fentanyl) are central; titrate to effect and proactively manage side effects like constipation.
• Adjuvant analgesics (gabapentinoids, TCAs, corticosteroids) are crucial for neuropathic or bone pain.
• Non-opioid analgesics (NSAIDs, paracetamol) are used for mild pain or as adjuncts; monitor NSAID toxicity.
• Interventional techniques (nerve blocks, neurolysis, spinal opioids) are considered for severe, refractory pain.
• Address breakthrough pain with short-acting opioids; regular pain assessment and reassessment are vital for effective therapy.