Özkan, Elgin

e21006 Background: Induction with novel biological agents has significantly improved progression free survival (PFS) of MM pts. However, role and timing of ASCT is unclear and there remains a need for a practical means to predict post-ASCT outcome. Our goal was to determine the prognostic value of FDG PET/CT (PET) after induction therapy (IT) in comparison with other prognostic factors and International Myeloma Working Group (IMWG) response criteria. Methods: Prospective, multicenter study of 113 newly diagnosed MM pts undergoing IT+ASCT. IT was not controlled and consisted of 2 or 3 novel agent combinations. The tested variables to predict PFS are shown in table. Two PET scoring systems were used: Score1, positive>marrow uptake; Score2, positive>liver uptake. ROC analysis determined the SUV cut-off. Results: With a median follow-up of 29.5 mo 56 (49.6%) pts relapsed (median PFS: 24.3 mo). Results are displayed in table. Post-IT, when a "+" PET (Score2) was associated with less than a VGPR response, relapses occurred in 83% of pts vs. in only 30% when PET was "-" and pts were in CR or VGPR. Multivariate analysis revealed only ISS to be an independent predictor of PFS (p=0.014). Conclusions: Post-IT a "-" PET associated with CR+VGPR suggests a durable response. Qualitative PET evaluation using a more liberal threshold (liver) to define positivity can be used to accurately assess response in MM. These data failed to prove the post-IT IMWG and PET response to be independent prognosticators while ISS was a superior predictor. This may be attributed to inadequate sample size, nonuniform pre- and post-ASCT treatments, varying follow-up times. Further analyses with stratifying various prognostic indicators and therapy schemes in a larger population are underway to determine a definitive role for PET as a predictor of post-ASCT outcome. [Table: see text]