8-530.1x:

You were treated with a radioactive drug because of cancer.

The tissue in the body is made up of cells. With cancer, the cells multiply uncontrollably, which leads to a malignant neoplasm (abnormal growth of tissue) developing. The cancer cells can destroy the healthy tissue and spread throughout the body. You have cancer cells accumulating in your bones. The cancer cells also affect and alter the neighboring bone cells. This can cause the bone tissue to multiply significantly and uncontrollably.

You have had a radioactive drug injected into a blood vessel. This drug accumulates specifically in the area where the bone tissue has multiplied significantly. When the drug is absorbed by the bone cells, it breaks down and emits radiation. The pathologically altered cells in your bones are to be destroyed by the emitted radiation. Radiation only works in a small area. This is to protect the surrounding healthy tissue.