Detection of focal myeloma lesions by technetium-99m-sestaMIBI scintigraphy

Background and Objective. The tracer technetium-99m-2-methoxy-isobutyl-ison itrile (Tc99m-sestaMIBI) has recently been shown to concentrate in some neo plastic tissues, including myeloma. We investigated the diagnostic capacity and limits of this procedure in tracing focal myeloma lesions, and compare d them with those of conventional radiological procedures (Xr). Design and Methods. We studied 55 patients suffering from multiple myeloma (MM) or solitary plasmacytoma in different stages and clinical conditions, or from monoclonal gammopathy of undefined significance (MGUS), by whole bo dy scans obtained 10 minutes after injection of 555 MBq of Tc99m-sestaMIBI. Scans were defined as normal (physiological uptake only), diffuse (presenc e of bone marrow uptake), or focal(localized areas of uptake), and were com pared to conventional skeletal Xr. Results. Thirty patients showed no focal areas of Tc99m-sestaMIBI uptake; t his group consisted of 5 patients with MGUS, 6 with MM in stage IA and 2 in stage IIA, 11 patients studied after effective chemotherapy and 6 in early relapse. Twenty-five patients showed one or more spots of focal uptake: al l of them had active disease (untreated, resistant or relapsing MM). In the setting of tracing focal lesions, Tc99m-sestaMIBI scans were concord ant with the radiological examination in 38 patients and discordant in 17. Among the latter, in 4 cases Tc99m-sestaMIBI revealed focal lesions not det ected by Xr, and in 13 cases lytic areas detected by Xr did not show Tc99m- sestaMIBI uptake. Interpretation and Conclusions. In untreated patients, the number of lesion s revealed by Tc99m-sestaMIBI was comparable to that shown by Xr, while in pretreated patients Tc99m-sestaMIBI traced a number of lesions lower than t hat detected by Xr. The reason for this discrepancy is that Tc99m-sestaMIBI traces only active lesions. Tc99m-sestaMIBI limitations in identifying foc al lesions may derive from the dimension of the smallest traceable lesion ( about one centimeter), and from the possibility that focal plasma cell loca lizations in collapsed bone may not be visualized due to inadequate vascula rization. Tc99m-sestaMIBI scintigraphy is an interesting tool for diagnosin g, staging and following up focal myeloma lesions, in the bone as well as i n soft tissues. It is more specific than conventional Xr in identifying sit es of active disease. (C)1999, Ferrata Storti Foundation.