Key Facts

Effective cancer pain management requires regular assessment, appropriate prescribing, and addressing the physical, psychological, social, and spiritual dimensions of pain (total pain concept — Cicely Saunders).

Epidemiology

• Pain affects 50% of patients at diagnosis and 70-80% with advanced disease
• Approximately 30% of cancer patients have pain that is difficult to control
• Undertreatment of cancer pain remains a significant problem

Aetiology

• Cancer-related (60-70%): tumour invasion of bone, nerve, viscera, soft tissue
• Treatment-related (20%): post-surgical, chemotherapy-induced neuropathy, radiation fibrosis
• Concurrent non-cancer pain (10-20%): musculoskeletal, neuropathic

Pathophysiology

• Nociceptive pain: somatic (well-localised, aching) or visceral (poorly localised, cramping, referred)
• Neuropathic pain: nerve compression or invasion; burning, shooting, tingling
• Bone pain: tumour stimulates osteoclasts → bone destruction → nociceptor activation; prostaglandin-mediated
• Central sensitisation: chronic pain leads to neuroplastic changes in the spinal cord and brain

Pain Assessment

• Location, character, severity (0-10 numerical rating scale)
• Temporal pattern (constant, intermittent, breakthrough)
• Aggravating and relieving factors
• Impact on function and quality of life
• Current analgesic use and effectiveness
• Side effects of current treatment

Pain Types

• Somatic: well-localised, aching, worsened by movement (bone metastases)
• Visceral: diffuse, cramping, poorly localised (liver capsule stretch, bowel obstruction)
• Neuropathic: burning, shooting, electric shock-like (nerve compression, chemotherapy-induced)
• Breakthrough pain: transient flares of pain on background of controlled baseline pain

Red Flags

• New back pain with neurological signs (spinal cord compression)
• Severe uncontrolled pain despite escalating opioids (consider nerve block, radiotherapy)
• Signs of opioid toxicity: myoclonus, confusion, hallucinations, pinpoint pupils
• Bone pain with risk of pathological fracture
• Pain crisis (severe uncontrolled pain requiring emergency management)

Bedside

• Pain assessment tool (numerical rating scale, Brief Pain Inventory)
• Neurological examination if neuropathic pain suspected
• Examination of pain site

Bloods

• U&Es (renal function for drug dosing and opioid metabolite accumulation)
• LFTs (hepatic metabolism of opioids)
• Calcium (hypercalcaemia as cause of pain)

Imaging

• Targeted imaging of pain site (X-ray, CT, MRI)
• Bone scan or PET-CT for bone metastases
• MRI spine if cord compression suspected

Special Tests

• Quantitative sensory testing (research setting)
• Nerve conduction studies (chemotherapy-induced neuropathy)
• Psychological assessment (pain catastrophising, depression)

Non-pharmacological

• Patient education about pain management
• Psychological support (CBT, relaxation techniques, mindfulness)
• Physiotherapy and occupational therapy
• TENS (adjunct for localised pain)
• Complementary therapies (massage, acupuncture — limited evidence)

Pharmacological

• Step 1 (mild pain): paracetamol 1g QDS ± NSAID (ibuprofen 400mg TDS or naproxen 250-500mg BD)
• Step 2 (moderate pain): codeine 30-60mg QDS or tramadol 50-100mg QDS (consider going directly to Step 3)
• Step 3 (severe pain):
  • Oral morphine: start 5-10mg IR (Oramorph) 4-hourly; titrate by 30-50% every 24-48 hours
  • Once stable: convert to modified-release (MST Continus) BD with IR morphine for breakthrough (1/6th of 24h dose)
  • Oxycodone: alternative if morphine poorly tolerated (start 5mg IR 4-6 hourly or 10mg MR BD)
  • Fentanyl patch: 12-25mcg/h every 72 hours (for stable pain in patients unable to take oral medication)
  • Buprenorphine patch: 5-70mcg/h every 7 days
• Adjuvant analgesics:
  • Neuropathic: amitriptyline 10-75mg ON, gabapentin 300-1,800mg daily (titrated), pregabalin 75-300mg BD
  • Bone pain: NSAID + dexamethasone 4-8mg daily; bisphosphonates (zoledronic acid 4mg IV monthly)
  • Visceral colic: hyoscine butylbromide 20mg QDS
  • Muscle spasm: baclofen 5-20mg TDS, diazepam 2-5mg TDS
• Always co-prescribe laxatives with opioids: senna 15mg ON + docusate 100mg BD or macrogol
• Antiemetics with opioid initiation: metoclopramide 10mg TDS or haloperidol 1.5mg ON (usually transient)

Surgical/Interventional

• Palliative radiotherapy: bone metastases (8Gy single fraction — 60-80% pain response)
• Nerve blocks: coeliac plexus block (pancreatic cancer), paravertebral block
• Intrathecal drug delivery: for refractory pain (intrathecal morphine, bupivacaine, ziconotide)
• Vertebroplasty/kyphoplasty: painful vertebral fractures
• Surgical stabilisation: prophylactic fixation for impending fractures

Referral Criteria

• Pain not controlled with standard analgesics: palliative care/pain specialist referral
• Neuropathic pain not responding to first-line agents: specialist input
• Consideration of interventional procedures: pain team referral
• Psychological distress associated with pain: psychology/psychiatry referral

• Adequate pain control achievable in >80% of cancer patients with WHO ladder approach
• 10-20% have refractory pain requiring specialist intervention
• Palliative RT for bone pain: response in 60-80%, complete response in 30%
• Neuropathic pain: often more difficult to treat; combination therapy usually needed
• Pain management significantly impacts quality of life, function, and survival

WHO Analgesic Ladder

Opioid Equianalgesic Doses (Approximate)