A doctor conducts a bone scan in men diagnosed with prostate cancer to determine if the cancer has spread to the bones, explains the American Cancer Society. When prostate cancer spreads, the bones of the pelvis, lower spine and upper thighs are often affected first, notes the Prostate Cancer Foundation.
During a bone scan, the patient receives an injection into his vein of low-level radioactive material, which settles in damaged areas of bone within a few hours of the injection, according to the American Cancer Society. The patient then lies on a table while a special camera detects the radioactivity to create a picture of the skeleton. Damaged bones attract the radioactive material and appear as hot spots on the images the camera produces. Hot spots may be indicative of bone cancer, but arthritis and other bone diseases can cause them. A doctor may order an X-ray, CT scan, MRI or bone scan to make an accurate diagnosis.
The bone scan helps the doctor assign a stage to the prostate cancer so that he can develop an appropriate treatment plan, reports Mayo Clinic. Prostate cancer that has spread to the bones is stage 4 prostate cancer. Doctors repeat bone scans periodically during treatment of prostate cancer to monitor results and make adjustments to the treatment protocol, states the Prostate Cancer Foundation.