P-044: Comparison of 10 Color Flowcytometry and PET/CT for prognosticating MM post-transplant: results from IMPOSE-BORTECON trial

Abstract

<h3>Background</h3> The primary hurdle in curing MM is defining a validated minimal residual disease (MRD). Commonly used techniques for assessing MRD in India are multicolor flow cytometry (MFC) and PET/CT. We intended to compare the efficacy of the 10 Color-MFC and PET/CT for prognosticating MM post-transplant. <h3>Methods</h3> The study is a prospective multicentric randomized controlled study – IMPOSE BORTECON (AFMRC-4905/2016). The primary objective was to compare the PET/CT and MFC for prognosticating the MM patients post-transplant for OS. The secondary objectives were to evaluate universal availability and applicability, patient satisfaction scoring, and financial implications of the MRD techniques. The data from patients enrolled till 31 Dec 2020 were analyzed. All patients underwent MFC and PET/CT (within seven days gap) starting D+100 post-transplant four times at six-monthly intervals. 18F-FDG-PET/CT was scored using IMPeTUs scoring with Deauville 3 considered as Positive (Target Lesion SUVmax > Liver SUVmax). Two readers interpreted the reports with a CoV of 1.2%. MFC was done using Beckmann Coulter, 10 Color 2 tube technique with standard antibodies as EMN guidelines, with the single reader, and all reports were counterchecked by the company scientist for accuracy. PFS and OS were defined as per IMWG guidelines. JMP 15.0 was used for data analysis. <h3>Results</h3> Of 106 patients constituting 434 simultaneous MRD evaluations, the median age was 52 years (35-66) with male preponderance (61.3%). Of all the patients analyzed, the 2y and 3y were 80% and 60.4%. 29.8% were positive for MRD by MFC, and 37.2% were positive for PET/CT. PET positivity was preceded by a mean of 102d before MFC positivity (SD-338d). On average, PET/CT was positive six months before the MFC and 12 months before clinical relapse by swimmer's analysis. PET/CT positivity was significantly associated with inferior OS compared to positive MFC (p<0.001, p-0.239 respectively) using Kaplan-Meier analysis. The concordance between MFC and PET-CT was not statistically significant (R=-0.101, p-0.7811). Universal availability of MFC was more difficult owing to a lack of standardization and expertise to report the test in real-world settings. On the evaluation of patient feedbacks, 18 patients withdrew consent due to fear of repeated bone marrows for MRD by MFC. Costs were comparable by Markov analysis. <h3>Conclusion</h3> We have reported higher efficacy of positive PET/CT in predicting the inferior OS than MFC in MM post-transplant. The results of the PET/CT are more easily interpretable, with PET/CT being more acceptable to patients and more widely available with no additional costs. This is the first study from our country to compare the two MRD analysis methods in MM patients.