Many terminally ill patients suffer from several types of pain.  The physical causes of pain in cancer patients can be divided into three categories:

1. Cancer related - for example a tumor is causing pain.  Approximately 70% of patients suffer from this type of pain.
   

2. Treatment related - for example radiation, surgery, or chemotherapy causes pain.  Approximately 15% of patients suffer from this type of pain.
   

3. Coincidental pain, which is pain unrelated to cancer or its therapy - for example decubiti.  Approximately 15% of patients suffer from this type of pain.

Some examples of different causes of pain include:

• Compression of nerve roots, trunks, or plexus by tumor

• Metastatic fracture of bone adjacent to nerves

• Infiltration of the nerves and blood vessels by tumor cells

• Obstruction of an organ, particularly the gut or urinary tract

• Partial or complete occlusion of blood vessels by an adjacent tumor

• Infiltration and swelling of tissue within fascia, periosteum, or other pain-sensitive structures

• Necrosis, infection, and inflammation of tissues sensitive to pain produced by nearby tumors of neoplastic disease

• Other pains, such as osteoarthritis, rheumatoid arthritis, thoracic and abdominal aneurysms, diabetic neuropathy, and osteoporosis