Cancer Pain Management

Cancer Pain Management Dr Simon Chan Pain Management Unit Dept of Anaesthesia and Intensive Care Prince of Wales Hospital

Pain - Definition • “… an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage” • International Association for the Study of Pain • Pain is biological useful because it signals injury or disease

Outlines • Pathophysiology of cancer pain • Mechanism of cancer pain • Assessment of cancer pain • Modalities of cancer pain management • Clinical aspects of cancer pain management

Pathophysiology of Cancer Pain

Pathophysiology of Cancer Pain • Three main factors contribute to the pathogenesis pain in cancer patients • Nociceptive pain • Neuropathic mechanism • Idiopathic (psychological) processes

Nociceptive Pain • Pain resulting from the activation of nociceptors in somatic or visceral structures • Nociceptive somatic pain – sharp, aching, throbbing or pressure-like • Visceral pain – poorly localized • Hollow viscus – cramping • Solid organ capsule or mesentery – sharp, aching • Responds well to all forms of analgesia

Neuropathic Mechanism • Results from abnormal functioning in the central or peripheral somatosensory system • Associated with dysesthesia, allodynia, hyperalgesia • Pain – burning or stabbing • Due to nerve lesion, surgery, chemo • Variable response to opioid

Idiopathic Pain • Pain that is not explained with the organic pathology • Diagnosed with extreme caution • Onset of symptoms could be long before imaging proven tumor growth

Mechanism of Cancer Pain

Mechanism of Cancer Pain • Pain syndrome related to direct tumor involvement • Pain syndrome due to cancer treatment

Direct Tumor Involvement • Infiltration of bone and joints • Commonly seen in Ca breast, lung, prostate • Pain usually localized, mechanical • Vertebral pain syndrome • Tumor infiltration of viscera • Distention of solid organ capsule • Obstruction of hollow viscus – GI, biliary, ureter • Direct tissue infiltration – pleura, peritoneum

Direct Tumor Involvement • Tumor infiltration of soft tissue • Skin, subcutaneous tissue, muscle • Compression of nervous tissues • Peripheral nerve, plexus, spinal cord • Tumor-related headache • Skull lesion,  ICP

Pain Related to Cancer Treatment • Post-surgical • Surgical trauma, non-healing incision • Neuropathic – mastectomy, thoracotomy, limb amputation • Post—radiotherapy syndrome • Inflammation of mucous membrane, fibrosis, osteoradionecrosis, myelopathy • Post-chemotherapy • Polyneuropathy, aseptic bone necrosis

Assessment of Cancer Pain

Assessment of Cancer Pain (1) • Multi-dimensional assessment • Believe the patients’ complaint of pain • Take a detail ‘pain history’ • Evaluate the response to previous and current analgesic therapies • Evaluate the psychological state of the patient • Physical and neurological examination

Assessment of Cancer Pain (2) • Appropriate diagnostic tests • Design the diagnostic and therapeutic approach to suit individual patient • Reassess the response to pain therapy regularly • Discuss advance directives with patients and family

Different Modalities of Pain Management • Pharmacological analgesia • Physical therapy • Psychotherapy • Interventional neural blockade • Neuro-ablation - surgical, percutaneous • Neuro-augmentation - dorsal column stimulation • Anti-cancer treatment

Physical Therapy • Therapeutic heat – superficial, short-wave diathermy, ultrasound • Therapeutic cold • Transcutaneous electrical nerve stimulation • Biofeedback and acupunture • Therapeutic exercise – strengthening, stretching, postural and relaxation exercise • Mobilization – traction, manipulation, massage • Hydrotherapy

Psychotherapy • Relaxation training • Behavioral therapy – aim to reduce pain behaviour • Cognitive restructuring to replace the maladaptive themes with more adaptive thoughts • Others – group, marital, family therapy and hypnosis

Pharmacological Analgesia in Cancer Pain • Appropriate drug for the cause of pain • WHO’s analgesic ladder • Round the clock • Oral route as the preferred route (alternate route if intolerant or side effects) • Individualize dosage • Anticipate side effects

+/- adjuvant +/- adjuvant +/- adjuvant WHO Analgesic Ladder Potent opioid Weak opioid Simple analgesia

Simple analgesia paracetamol NSAIDs musculoskeletal pain side effects Anti-depressants descending modulating pathway neuropathic pain Anti-convulsants neuropathic pain Membrane stabilizer neuropathic pain Muscle relaxant Baclofen Non-Narcotic (Adjuvant) Analgesia

Opioid Analgesia • Choice of opioid • potent vs weak • side effect profile • pharmacokinetic properties • Route of administration • Systemic - IV, IM, PCA • Oral • Spinal - epidural, intrathecal • Novel route

Patient-Controlled Analgesia:PCA Pumps • Technological Improvements • Smaller • More ambulatory • Battery life • Memory

Common Side Effects of Opioid • Sedation • Nausea and vomiting • Constipation • Urinary retention • Pruritus • Reactivation of herpes simplex

Opioid Responsiveness • Defined as the probability that adequate analgesia (satisfactory relief without intolerable and unmanageable side effects) can be attained during gradual dose titration. • ie degree of analgesia obtained at treatment-limiting toxicity

Strategies for Poor Opioid Responsiveness • Opening the “therapeutic window” • Aggressive side effect treatment, eg psychostimulant for sedation • Opioid rotation • Pharmacological techniques to reduce the systemic opioid requirement • Adjuvant analgesia • Neuraxial drug administration • Interventional neural blockade

+/- adjuvant +/- adjuvant +/- adjuvant WHO Analgesic Ladder Interventional Neural Blockade Potent opioid Weak opioid Simple analgesia

Neuro-Ablation • Percutaneous • chemical • radio-frequency • Cryoanalgesia • Neurosurgical

Interventional Neural Blockade • Peripheral nerve blockade • diagnostic • prognostic before neuro-ablation • therapeutic • Visceral denervation • Spinal administration of drugs • Chemical sympathectomy

Epidural Analgesia • Agents - LA, opioid • Avoid side effects of systemic opioid

Spinal Opioid • Systemic : epidural : intrathecal = 30:10:1 • Pharmacological side effects • delayed respiratory depression • urinary retention • pruritus • herpes simplex • systemic side effects

Spinal Opioid - Mode of delivery • intermittent vs continuous infusion • patient control vs nurse control • percutaneous vs implantable • mechanical vs electronic pump

Anti-Cancer Treatment • Radiotherapy • Intra-cranial lesion • Bony metastasis for pain control and avoid spinal cord compression • Chemotherapy • Tumor shrinkage • Steroid (dexamethasone) • Reduce tissue swelling form tumor compression

Multidisciplinary Approach to Pain Management • Oncologist • Palliative care physician • Surgeon (Neurosurgeon, Orthopaedic) • Nurse – Pain, palliative care, community • Physiotherapist • Psychologist/ Psychiatrist • Occupational therapist • Anesthesiologist

PAIN

Cancer Pain Management