Quantification of Changes in Bone Scans of Patients with Osseous Metastases of Prostatic Carcinoma

Abstract

No imaging modality is more effective in screening the entire skeleton for metastatic deposits than the radiopharmaceutical bone scan. Thus, while conventional skeletal imaging’s primary indication is for the detection of focal bone disease, such information may not readily document tumor response to therapy [1]. In addition, although bone scans are highly sensitive to localized skeletal abnormalities, they are nonspecific as to the cause of increased radiopharmaceutical uptake [2]. In an attempt to increase our understanding of how prostate cancer patients handle Tc-99^m methylene diphosphonate (MDP) we have investigated the usefulness of a method which determines the 24 hour total body retention of this tracer in these individuals. Previous publications report this value to be an indicator of global metastatic skeletal burden which significantly differentiates the various clinical stages of prostatic cancer [3–5]. The present study determines the 24-hour retention value of Tc-99^m MDP in a group of prostate cancer patients on a longitudinal basis during therapy. The chronic retention changes in the same patient as a function of time are compared with more established objective and subjective criteria. The significance of this method would be a function of its magnitude of change when a particular patient enters relapse or remission during their course of therapy.