Rationale for the use of bone scans in selected metastatic and primary bone tumors.

Since the introduction of bone scans in 1951, there have been many studies comparing biologic and physical characteristics of new bone-imaging agents and the results of scintigraphy and radiology in large numbers of patients. Relatively speaking, there have been fewer studies detailing the health benefits and financial cost associated with the use of skeletal scintigraphy. This review concerns these aspects in patients with malignancies of various sites and stages. About 2% of patients with stage I or II breast cancer have bone metastases at the time they first present, whereas nearly 28% of patients with stage III disease have bone metastases. A large percentage of patients with initially negative scans develop bone metastases during the first 3--4 yr; many of them develop them within the first 12--18 mo after initial diagnosis. For patients with lung cancer, the use of bone scans in staging their disease is somewhat controversial. Several studies indicate that the yield of positive bone scans may range from as low as 2% to as high as 35%. Data on the use of bone scans in staging prostatic cancer initially are similar to those in patients with breast cancer, that is, yields of 7% in patients with stage I or II disease and a yield of about 20% with stage III disease. Children with osteosarcoma or Ewing's sarcoma rarely have bone disease distant from the site of their primary bone lesion at presentation. However, a large percentage of them (30%--40% or so) develop bone metastases during the follow-up period. As in the case with patients with breast cancer, about half of these bone metastases are evident by 12--18 mo.