Could cancer be causing my chronic pain?

Cancer can certainly cause severe pain by compressing nearby structures as it grows or spreading (metastasizing) to bones of the spine or internal organs. Typically, by the time the cancer metastasizes to bone, patients experience other symptoms such as progressive weight loss, night sweats, swollen lymph nodes and symptoms from the organ where cancer started (for example cough for lung cancer or lump on breast examination for breast cancer). So if your pain started without a specific cause (like a fall or a car accident) and keeps getting worse, especially if it is associated with unexplained weight loss investigating for malignancy is very important.

On the other hand if your pain started after a fall or car accident, and it has been present for over a year without any associated symptoms such as weight loss or fever, cancer as the cause of your pain is highly unlikely. The longer your pain has been present, the less likely it is caused by cancer as cancer kills often within months without treatment, and you are still alive.

Having said all that investigations may still be worth doing especially if there is history of cancer in the past or person starts to develop unexplained weight loss or fever.