Bone imaging in prostate cancer

Bone metastases of solid tumors are common, and about 80% of them occur in patients with breast, lung or prostate cancer. Bone metastases can be suspected clinically and by laboratory tests; however, a final diagnosis relies on radiographic evidence. Bone metastases of prostate cancer usually have osteoblastic characteristics, manifested by pathological bone resorption and formation. Conventional bone scans (e.g. with (99m)Tc-labeled methylene diphosphonate) are preferred to plain-film radiography for surveillance of the entire skeleton. Radiologic diagnosis of bone metastases, particularly in patients with low burden of disease, is difficult because noncancerous bone lesions that mimic cancer are common. Conventional bone scans are limited by their low sensitivity and high false-negative rate (up to 40%) compared with advanced bone-imaging modalities such as PET, PET-CT and MRI, which might assist or replace conventional scanning methods. The correct diagnosis of bone involvement in prostate cancer is crucial to assess the effects of therapy on the primary tumor, the patient's prognosis, and the efficacy of bone-specific treatments that can reduce future bone-associated morbidity. In addition, predictive tools such as nomograms enable the identification of patients at risk of bone involvement during the course of their disease. Such tools may limit treatment costs by avoidance of unnecessary tests and might reduce both short-term and long-term complication rates.