Metastatic Bone Disease

Overview

Metastatic bone disease (MBD) is the most frequent malignant bone condition. It reflects the spread of systemic cancer to the skeletal system, typically in advanced disease stages. Common primary sites include breast, prostate, lung, kidney, and thyroid.

Clinical Presentation

• Persistent bone pain (often worse at night)

• Pathological fractures

• Neurologic symptoms (if spine is involved)

• Hypercalcemia-related symptoms (confusion, nausea)

• Systemic cancer signs (weight loss, fatigue)

Common Primary Tumours Causing Bone Metastases

• Breast:  Most common in ♀, more than  >%50 are blastic

• Prostate:  Mostly sclerotic/blastic lesions, spine predilection, most common in ♂

• Lung: Lytic, often aggressive

• Kidney (RCC): Lytic, vascular; surgical bleeding risk

• Thyroid: Often solitary, lytic, surgical bleeding risk

Frequent Skeletal Sites Involved

• Spine (especially thoracic)

• Pelvis

• Proximal femur

• Humerus

• Ribs

• Skull

Imaging

• X-Ray: Lytic/blastic/mixed lesions; cortical breach 

• CT : Useful for bone imaging and thorax-abdominal metastatic screening.

• MRI: Marrow involvement, spinal cord assessment

• Bone Scan: Detects most metastases, but misses pure lytic lesions

• PET-CT: Helps detect unknown primaries and whole-body disease burden

Biopsy Strategy

• Core needle biopsy is preferred

• Always after imaging

• Histopathology reflects the primary tumour (e.g., adenocarcinoma in breast CA)

Treatment Principles :

Depends on survey expectation 

Non-Surgical

• Short life expectancy / If the damage caused by surgery is greater than the tumor itself

• External beam radiotherapy for pain and local control (It can be used alone or after surgery.)

• Bisphosphonates or Denosumab (reduce skeletal-related events) > complication ; osteonecrosis of the jaw

• Systemic therapy based on primary tumour (Chemotherapy and hormone therapy depends on receptor posivity )

• Embolization ; especially for thyroid and renal cancers for reducing blood loss

• Pain control, bracing for support

Surgical Indications

• Impending or complete pathological fracture

• Neurologic compromise (cord compression)

• Solitary lesion in a patient with long survival

• Intractable pain

Surgical Techniques

• Plate fixation with curettage + cementation : In areas close to the joint like elbow, wrist and ankle

• Intramedullary nailing: Diaphyseal long bones

• Endoprosthetic reconstruction: Proximal femur/humerus : relatively long life expectancy

• Curettage + cementation: For small, contained lesions; can be combined with implant fixation

• Spine decompression and fixation: In cord compression

Prognosis & Decision-Making

• Life expectancy is key (although controversial; ideally >3–6 months for surgery)

• The Mirels criteria are less useful in the upper extremities. A score of 7 or higher is in the upper extremities, and a score of 9 or higher is an indication for fixation for impending fractures in the lower extremities.

• Some tools like Pathfx 3.0 helps to estimate. (https://www.pathfx.org/) 

• Prognostic scoring systems: Tomita , Tokuhashi

• Avoid major surgery in patients with short survival

Differential Diagnosis

• Multiple myeloma

• Lymphoma

• Primary bone tumours

• Bone infections

Sources:

• Campbell’s Operative Orthopaedics, 14th Edition

• WHO Classification of Bone Tumours, 2020

• Current Orthopaedic Oncology guideline

• Mirels' score for upper limb metastatic lesions: do we need a different cutoff for recommending prophylactic fixation? doi: 10.1016/j.jseint.2022.03.006. eCollection 2022 Jul.. 2022 Apr 25;6(4):675-681.JSES Int.Hoban et al. 

• External validation of the PATHFx decision-support tool on Turkish patients with skeletal metastasis. 2023 Feb 27.Indian J Cancer. Ozkan et al. doi: 10.4103/ijc.IJC_417_20.