Abstract
8533
Background: In a high risk population of pts with newly diagnosed or primary refractory MM, we prospectively studied FDG PET imaging to determine the value of PET/CT in assessing therapeutic response. Methods: Forty pts with high-risk MM defined as ISS II, ISS III or presence of extramedullary plasmacytoma have been enrolled on study and treated using a combination of bortezomib, pegylated liposomal doxorubicin hydrochloride (Doxil), and dexamethasone (BDD) for 3 cycles followed by 2 cycles of thalidomide and dexamethasone for patients achieving at least PR. Pts were assessed using serial FDG PET imaging: at baseline (BL), after 3 cycles of BDD and at end of study (EOS). FDG PET response was determined using European Organization for research and treatment of cancer (EORTC) recommendations. MM disease response was assessed according to the International Myeloma Working Group (IMWG) criteria. Results: Median age of pts enrolled was 59 yrs (range 41–80), 62% male, 38% ISS II, 47% ISS III, and 15% ISS I with soft-tissue disease. Thirty-five percent (14/40) had soft-tissue involvement with MM. At completion of protocol therapy, the ORR was 79%, with 44% of pts achieving CR/nCR and 59% ≥ VGPR. Ninety FDG PET scans were performed in 40 pts; 25 pts were evaluable for FDG PET response. The other pts are as follows: 2 had negative FDG PET at BL, 6 were taken off study (5 for toxicity and 1 with CR), 1 FDG PET was unable to be compared due to technical differences and 6 pts have not completed treatment. Seventeen of the 25 pts had PR by FDG PET, 5 had SD and 3 PD; none of the pts had CR. There was little agreement between MM disease response and FDG PET responses (Kappa statistic, 0.05). Three pts with PD by FDG PET, had PR (n=2) or CR (n=1) by IMWG criteria. One had granulomatous disease rather than MM at biopsy. In 1 pt with progression of disease with a progressive skull-based plasmacytoma, FDG PET was scored as PR by EORTC criteria. Conclusions: There was poor agreement between FDG PET response and MM disease response by IMWG criteria. Serial FDG PET did not provide additional information for therapeutic response assessment in pts with newly diagnosed or primary refractory MM.
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