85Sr bone scan in neoplastic disease

Abstract

The skeleton is a frequent site of metastases from neoplasms that are primary elsewhere. Bone scanning was introduced in 1961 to detect enhanced localization of 85 Sr at the sites of skeletal abnormalities. After 10 yr of experience with the bone scan, certain conclusions can be proposed. The bone scan is not helpful in the evaluation of diseases that diffusely affect the skeleton, but it is a sensitive method for detecting diseases that elicit a localized reparative reaction of the skeleton. Approximately 10–40% of patients with skeletal metastases have a normal skeletal roentgenogram at a time when the bone scan is abnormal, whereas less than 5% of bone scans are normal at a time when the skeletal roentgenogram reveals localized abnormalities. False positive bone scans can be reduced to considerably less than 1% through a knowledge of the mechanisms of localization of 85 Sr. The bone scan is particularly useful in patients with lymphomatous diseases and carcinoma of the lung, prostate, breast, and oropharynx. The serum alkaline and acid phosphatases are not sensitive enough for the detection of skeletal metastases. The primary limitation of bone scanning has been, and to some extent remains, the length of time required to accomplish the technical portion of the procedure. However, improved instrumentation and short-lived radiopharmaceuticals promise to make bone scanning feasible as a survey procedure. A certain amount of caution is still in order before accepting short-lived radiopharmaceuticals as a replacement for 85 Sr.