Approximately 35 to 40 per cent of cancer patients undergoing active treatment have pain; 60 to 90 per cent with advanced cancer have pain. Bone metastases are the commonest cause of pain in cancer; hence, tumours which spread to bone commonly cause pain (e.g. breast, lung, GI, GU).

Accurate diagnosis of the cause of pain is essential to successful treatment. The following outline is helpful in making an accurate pain diagnosis.

Pain Due to Local and/or Distant Spread of Tumour

(about 80 per cent of cancer pain)

1. Bone
   • skull, especially base, often with cranial nerve lesions
   • vertebrae, often with spinal cord and/or root compression
   • long bones, ribs, pelvis
2. Nerve
   • brain, with headache, often due to raised intracranial pressure
   • meninges, with headache, neck and back and/or leg pain
   • spinal cord and/or nerve root compression
   • plexus - brachial (especially in lung, breast, lymphoma, melanoma)
   • lumbosacral (especially in GI, GU, lymphoma, melanoma)
3. Soft tissue
   • head and neck tumours
   • obstruction of hollow organ (bowel, ureter)
   • stretching of capsule of solid organ (liver, kidney)

Pain Due to Treatment of Cancer

(about 15 per cent of cancer pain)

1. Post-Surgery
   • following radical neck dissection, mastectomy, thoracotomy, amputation
2. Post-Chemotherapy
   • peripheral neuropathy
   • post-herpetic neuralgia
   • aseptic necrosis of bone
   • steroid pseudorheumatism
3. Post-Irradiation
   • plexopathy, myelopathy
   • necrosis of bone

Pain Unrelated to Cancer or Its Treatment

(about 5 per cent of cancer pain)

E.g. migraine, pain due to degenerative disc disease, osteoarthritis, peptic ulcer, etc.

Pain Related to Chronic Debility

Chronic constipation, sore mouth, bursitis, myofascial pain (especially shoulder and hip girdles, back), deep vein thrombosis, bedsores, mucocutaneous ulceration, etc., may occur in the setting of chronic illness such as cancer. Effective treatment depends on accurate diagnosis.