Is FDG PET a better imaging tool than somatostatin receptor scintigraphy in patients with relapsing multiple myeloma?

Osseous involvement defined by lytic bone lesions is shown by skeletal survey in multiple myeloma (MM). This technique has limitations because it detects only lesions with more than 30% trabecular bone loss. In addition, lesions persist after chemotherapy, thereby limiting its usefulness at relapsing disease. Alternative techniques to detect new bone lesions are somatostatin receptor scintigraphy (SRS) and 18F-fluordeoxyglucose (FDG) PET so far predominantly studied in patients with newly diagnosed MM. Malignant plasma cells can have a high expression of somatostatin receptors and an elevated metabolic activity. Therefore, these techniques might be useful in patients with relapsing MM because they are not hampered by preexisting skeletal defects. The purpose of this study was to demonstrate which technique is most optimal to detect skeletal lesions in patients with relapsing MM.

In patients with relapsing MM (n = 21), 3 separate methods were used (skeletal survey, SRS, and FDG PET) for detecting new skeletal lesions.

Of all patients, 55% had new lesions on the skeletal survey [mean (SD), 1.45 (1.76); range, 0-5], 52% had new SRS lesions [mean (SD), 1.43 (0.38); range, 0-5], and 71% demonstrated new lesions on the FDG PET-scan [mean (SD), 4.05 (0.9); range, 0-12]. The lesions on skeletal survey and SRS corresponded with FDG PET. The number of lesions was higher with the FDG PET versus that with SRS (P = 0.01) and with FDG PET versus that with skeletal survey (P = 0.01).

The results demonstrate that FDG PET is more valuable than skeletal survey and SRS to detect disease activity in relapsing MM.