bony mets (metastases)

Last edited 01/2021 and last reviewed 06/2021

Primary tumours which give rise to metastases to bone are remembered by many students by the nonsense rule that they all begin with a B. Thus:

• breast
• bronchus
• byroid (thyroid)
• bidney (kidney)
• bostate (prostate)
• (rarely, bowel)

Note that all cancers (including malignant melanoma and haematological malignancies eg,lymphoma) can metastasise to bone (1)

More than 66% of metastatic secondaries to bone arise from breast or prostate.

Metastases to bone usually occur in areas that contain red marrow. Metastatic deposits destroy and replace bone, partly by their own expansion and partly by stimulating active bone resorption

• five commonest sites for bone metastases are:
• vertebrae,
• pelvis,
• ribs,
• femurs,
• and skull
• however metastases can occur in any bone

Possible symptoms of boney metastasis include:

• symptoms of hypercalcaemia, including nausea/vomiting, anorexia, constipation, muscle weakness, polyuria, and confusion
• neurological abnormalties can occur secondary to vertebral metastases as a result of spinal nerve root involvement
• note that metastatic spinal cord compression is an emergency and requires same day secondary care referral
  • possible presenting features include severe back or abdominal pain with associated sensorimotor deficits and/or features of cauda equina syndrome
• skull metastasis is less common
• presentation may include localised pain with or without features of local nerve impingement eg facial palsy

Blood tests if considering boney metastases include:

• full blood count, urea and electrolytes, bone profile (including corrected calcium and alkaline phosphatase), albumin,and any relevant tumour markers (eg, prostate specific antigen)
• seek urgent specialist input if moderate to severe hypercalcaemia (>3 mmol/L) as often requires in patient management

Key Considerations (2):

• Red flag symptoms for cancer related bone pain include:
• severe progressive pain that is worse on movement or at night,
• inability to weight bear,
• signs of hypercalcaemia,
• and pain on direct palpation
• initial radiographs may be normal
• metastases may not show up on radiographs until 50-70% of the bone has been destroyed
• Mirels'score can be used to predict risk of fracture based on:
• metastasis location,
• size,
• radiographic appearance,
• and pain
• the use of prophylactic fixation i.e. before a pathological fracture occurs
• leads to better outcomes in terms of pain relief, hospital stay, and function
• even if prognosis is poor
• surgery can relieve pain, improve function, and maximise independence, and is usually of benefit

Reference:

• Zajaczkowska R et al. Bone pain in cancer patients:mechanisms and current treatment.Int J Mol Sci2019;20:6047.doi: 10.3390/ijms20236047 pmid: 31801267
• Downie S et al. Diagnosis and referral of adults with suspected bony metastases. BMJ 2021;372:n98http://dx.doi.org/10.1136/bmj.n9