RT Journal Article SR Electronic T1 Evaluation of response to treatment in multiple myeloma patients by a semi-automated FDG-PET/CT quantification method JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 23 OP 23 VO 60 IS supplement 1 A1 Mahdi Zirakchian Zadeh A1 Brian Ostergaard A1 William Raynor A1 Cyrus Ayubcha A1 Oswaldo Acosta-Montenegro A1 Siavash Mehdizadeh Seraj A1 Oke Gerke A1 Caius Constantinescu A1 Thomas Werner A1 Hongming Zhuang A1 Poul Flemming Hoilund-Carlsen A1 Abass Alavi YR 2019 UL http://jnm.snmjournals.org/content/60/supplement_1/23.abstract AB 23Objectives: According to the International Myeloma Working Group, the current methods of FDG-PET quantification for assessment of multiple myeloma (MM) patients suffer from some shortcomings, mainly a lack of reproducibility. We evaluated the treatment responses of MM patients through a novel method of PET/CT quantification which considers the total bone marrow activity [global metabolic activity score (GMAS)]. We aimed to assess the degree of reproducibility and also evaluate the correlation of GMAS with survival data, determining whether GMAS could predict the patients’ prognosis. Methods: Thirty MM patients (median age 65.5 years, range: 50-81), who had FDG-PET/CT scans at baseline and post-treatment were collected from the FULIMA prospective study. The patients were followed for up to 55 months (median 40, range 3-55) after the treatment. Subsequent to the co-registration of PET and CT data, a threshold algorithm on the Hounsfield scale was applied to quantify the whole bone marrow (WBM) FDG uptake of the subjects (OsiriX software; Pixmeo; Bernex, Switzerland). The WBM FDG uptake was multiplied by the whole bone marrow volume. Cut-offs for Kaplan-Meier curves were obtained from ROC analysis. The correlations of GMAS with overall survival (OS) and progression-free survival (PFS) were assessed. All measurements were replicated by two separate observers. Results: We observed a statistically significant decrease in GMAS after treatment. Pre-treatment GMAS did not correlate with OS and PFS, but there was a significant difference between the OS of the patients with the post-treatment GMAS over 5276 in comparison to GMAS below that value (log rank p=0.01). Univariate Cox regression analysis found that post-treatment GMAS was a significant predictor of inferior OS (HR: 9.54, 95% CI: 1.06-85.67; p= 0.04). Furthermore, in stepwise forward multivariate Cox regression, higher post-treatment GMAS was associated with inferior OS (HR: 10.34, 95% CI: 1.15-92.88; p= 0.03). The results for PFS were not significant. Inter-rater agreement was found to be high (concordance correlation coefficient (ρc) = 0.994, lower one-sided 95% CL: 0.989, lower two-sided 95% CL: 0.987, upper one-sided 95% CL: 0.997, upper two-sided 95% CL: 0.997). Conclusions: Our application of a global WBM assessment indicated that higher GMAS measured on FDG-PET/CT imaging performed at the end of therapy was associated with inferior OS. High level of agreement was observed between two observers.