- Pre-existing pain conditions
- (Mass) effects of the tumour itself
- Inflammation
- Compression e.g. of nerves
- Ischaemia e.g. impinging on vasculature
- Oedema e.g. interrupted venous/lymphatic drainage
- Paraneoplastic phenomena
- Production of anti-Hu and anti-Yo neuronal antibodies causes peripheral neuropathy/neuritis
- Effects of the disease process
- Osteoporosis ± pathological fractures
- Hypercalcaemia
- Infection
- Prolonged immobility and pressure sores etc.
- Effects of treatment
- Chronic post-surgical pain
- Post-radiotherapy neuritis
- Chemotherapy-induced peripheral neuropathy
Cancer Pain
Cancer Pain
The curriculum asks us to describe 'the basic assessment and management of cancer pain in adults'.
This topic was an SAQ in 2018, but its 86% pass rate seems to have put the examiners off repeating it since then.
Resources
- Pain is a common symptom in those with malignant disease
- Its aetiology is multifactorial and therefore may be difficult to treat
- Grief counselling
- Cognitive behavioural therapy
- Relaxation techniques
- Pain management programmes
- Complementary therapies e.g.:
- Acupuncture
- Reflexology
- Herbal remedies
- Reiki
- The WHO analgesic ladder can be used as a guide, though may need strong opioids earlier
Opioids
- Opioids are, in general, very effective
- Initially low-dose, long-acting opioids are used
- The dose is up-titrated e.g. by 30 - 50% over a few days until symptom control is achieved
- Breakthrough pain can be managed with shorter-acting variants e.g. PRN oral morphine dose at 1/6th total daily morphine dose
- Morphine doses >120mg associated with increased side effects without additional benefit
- Patients on such high doses (e.g. >60mg morphine/24hrs) may benefit from fentanyl patches
- Opioids have multiple side-effects and may cause opioid-induced hyperalgesia, a paradoxical increase in pain
- Reduction in opioid dose should be the first action in this case
- Administration of alternative analgesics and pharmacotherapy for side-effects should follow
- Opioid rotation to oxycodone may be necessary
- In patients with a low eGFR, oxycodone (<30ml/min) or alfentanil CSCI (<20ml/min) are used instead
- Treat side-effects of opioids e.g. with laxatives
Adjuncts
- NMDA antagonists e.g. ketamine, methadone
- Gabapentinoids for neuropathic pain
- Anti-spasmodics e.g. hyoscine
- Steroids to reduce local mass effects
- Cannabinoids (not licensed in the UK)
- Bisphosphonates for bone pain due to metastases or osteoporosis
- Do not target solitary metastases and may be more appropriate when there is scattered pain
- Only modest pain reductions; less effective than radiotherapy
- Poor PO bioavailability and should be given as IV infusion
- Best evidence is in bony metastases from breast cancer, multiple myeloma and prostate cancer
Oncological
- Chemotherapy
- Radiotherapy
- Localised external beam radiotherapy to target individual metastases, especially if opioid-refractory
- Initial flare in pain from skin reaction to radiotherapy for 7 - 10 days
- Subsequent reduction in pain as bony sclerosis occurs over 4 - 6 weeks
- 80% of patients respond
- Wide field radiotherapy can be efficacious for localised bone pain, with response in 60% of patients (NNT 3.6)
- Hormonal therapy e.g. tamoxifen
- Immunotherapy e.g. herceptin
- Radio-isotope treatment for multiple bony metastases e.g. IV strontium-89 is as efficacious as wide field radiotherapy but with fewer side effects
Interventional
- One can target neural pathways at different levels:
- Central e.g. IT neurolysis, neuraxial infusions, cervical cordotomy
- Visceral (autonomic nervous system) e.g. coeliac plexus block, superior hypogastric block, ganglion of impar block
- Peripheral (somatic) e.g. radiofrequency ablation or pulse current application, nerve block using phenol
Surgical
- Curative surgery
- CSF shunt procedures
- Management of pathological fractures, but no benefit to fixation without fracture
- Management of bowel obstruction
- Spinal cord stimulators