Aim: The objective of this study was to analyze the prognostic value of 18F-FDG PET/CT after therapy in patients with multiple myeloma (MM).
Patients and Methods: One hundred seven patients prospectively recruited with MM had FDG PET/CT at staging 3 months after therapy (autologous stem cell transplantation) and every 6 to 12 months during the follow-up (mean 41 months). Patients were divided into group 1 (relapsed) and group 2 (nonrelapsed). In group 1, PET results and SUVmax were compared to the time to relapse (TTR). In group 2, the presence of PET finding changes during follow-up was analyzed to identify typical patterns of disease behavior (ie, late responders or stabilized disease). Patients with a negative PET at staging were excluded from further evaluation.
Results: Forty-seven out of 107 (44%) patients relapsed: 10 were excluded because of a negative PET at staging. In group 1, 22 patients had a negative posttherapy PET (59%, mean TTR = 27.6 months) and 15 had a positive posttherapy PET (41%, mean TTR = 18 months). There was a significant difference between the TTR of the two subgroups (t test P = 0.05). In patients with a positive posttherapy PET, the SUVmax was inversely correlated to the TTR (correlation coefficient = −0.7; P < 0.01).
Sixty out of 107 (56%) patients did not relapse. Twenty patients were excluded because of a negative PET at staging. In group 2, 27 patients had a negative posttherapy PET (68%) and 13 had a positive posttherapy PET (32%). None of nonrelapsed patients showed a progressive increase in SUVmax during the follow-up. There was no significant difference between relapsed and nonrelapsed patients in terms of SUVmax at posttherapy PET/CT (t test P = 0.7).
Conclusion: In our series of MM patients, a negative posttherapy PET was predictive for nonrelapse or a long disease-free survival. In contrast, a persistent significantly increased SUVmax after therapy was correlated to a short TTR.