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Epidemiology. Osseous metastases is the most common cause of intractable pain in cancer patientsThird common site of spread after lung and liverPresentation occurs after primary diagnosis in majority of patientsBut in 23% of patients it is the presenting problem which leads to the discovery of di
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1. Palliation of Metastases Iftekhar Ahmad, MD
Wayne State University/KCI
July 8thth, 2008
2. Epidemiology Osseous metastases is the most common cause of intractable pain in cancer patients
Third common site of spread after lung and liver
Presentation occurs after primary diagnosis in majority of patients
But in 23% of patients it is the presenting problem which leads to the discovery of disease
3. Pathophysiology Tumor cells primarily gain access to the circulation through the capillaries
1). Release of tumor cells from the primary
2). Invasion of vascular or lymphatic channels
3). Dissemination to distant sites
4). Endothelial attachment and invasion of new host
5). Growth into a metastatic focus
4. Pathophysiology Skeletal blood flow accounts for only 4-10% of total cardiac output
Incidence of skeletal metastases appears higher than expected
Microstructure of marrow renders it vulnerable to tumor accumulation and invasion
Arteries tend to divide capillaries as they near the endosteal margin of bone
Capillaries become continuous with venous system which has a 6-8 times capacity
The circulation comes to a near standstill at this point potentially allowing tumor cells more time to invade
5. Pathophysiology Tumor angiongenesis factor attracts vessels to a small tumor colony
Otherwise it would be dependant on local tissue circulation and incapable of further invasion
The production of this factor is partially blocked by immune responses so it may take years to have adequate vasculature for invasion
6. Mediators Some tumors produce and secrete humeral mediators that stimulate osteoclast activity:
TGF
PDGF
TNF
Prostaglandins
Interleukins
7. Distribution More prevalent in the axial skeleton versus the appendicular skeleton
But richer blood flow in appendicular skeleton would predict higher rates
8. Imaging Plain X-rays are the fastest form of imaging
Medulla involved early and cortex late
Role for patients with pain and positive bone scan to uncover pathologic fractures
Sclerotic: Prostate, Breast, GI, Bladder
Lytic: All sites
Mixed: Breast
More than 50% cortical destruction needed to detect