Post-Treatment (not interim) PET-CT Scan Status Is Highly Predictive of Outcome In Mantle Cell Lymphoma Treated with R-Hypercvad or ASCT

Abstract 3131 Introduction: Although MCL is reported to be an FDG-avid NHL subtype, PET-CT is not currently recommended in the modified IWG criteria (Chesen et al , JCO 2007) to stage, survey and assess treatment response in MCL. PET-CT is however frequently used for these purposes in clinical practice in MCL. Although convincing data exists regarding the prognostic utility of PET-CT imaging in Hodgkin Lymphoma (interim & post treatment) and DLBCL (post treatment), its prognostic utility both during treatment and immediately following treatment have not systematically been evaluated in a large MCL patient cohort to support its use in clinical practice. Methods: We conducted a two-center (JTCC & UPenn), retrospective cohort study to examine the prognostic utility of pre-treatment (PET-1), interim-treatment (PET-2 after 2–3 treatment cycles) and post-treatment PET-CT (PET-3) imaging in a uniform MCL patient cohort undergoing dose-intensive chemotherapy (R-HCVAD) or high-dose chemotherapy followed by autologous stem (ASCT) cell rescue in the 1st line setting. The primary study endpoints were PFS and OS. PET-CT images were centrally reviewed for the purposes of this study using standardized response criteria proposed by the Imaging Subcommittee of International Harmonization Project in Lymphoma (Juweid et al , JCO 2007). Radiologists were blinded to clinical outcomes at the time of PET-CT review and results were dichotomized at each time point and their concomitant SUV max at a suspected site of disease was recorded. Result: 82 pts (median age 61, range 35–95) with advanced stage (98% stage IV) MCL with PET-CT data were identified for this analysis. Of these, 57 pts were treated with R-HCVAD (50) or ASCT (7) in the first-line setting. 154 PET-CT scans were reviewed. Overall treatment response rate (IWG) was 93% (76% CR + 17%PR). With median follow-up of 23 months (disease progression) and 27 months (overall survival), 3 year PFS and OS estimates were 70% (CI 53–82%) and 82% (CI 65–91%) respectively. Median baseline characteristics: WBC 7.4, ECOG PS 1, LDH/ULN .82, Ki-67 (MIB-1) 28% (range 10–90%), MIPI 3.5 (31% intermediate risk, 19% high risk). 20% and 30% of pts were blastoid variant and leukemic phase at diagnosis respectively. Pre-treatment PET-CTs were FDG-avid in 92% of MCL patients with a median SUV max of 7.8 (range 2.4–36.7) at a suspected site of disease. Pre-treatment PET-CT SUV max was positively associated with high Ki-67 (variance-weighted least-squares regression, p=.01). PET-2 and PET-3 were positive in 34% and 18% of patients respectively. Kaplan Meier and Cox regression survival analyses were used to test the association between PET-CT and survival. Interim PET-CT status was not associated with PFS (HR 1.1, CI .4-3.6, p=.8) or OS (HR .8, CI .15-4.6, p=.8). Post treatment PET-CT status was statistically significantly associated with PFS (HR 5.4, CI 2.0–14.5, p=.001, Harrell9s C =.70, Figure) and trended towards significant for OS (HR 3.2, CI .8-11.9, p=.1). Post treatment PET-CT status remained an independent predictor of PFS in multivariate analysis which included MIPI score, blastoid variant and Ki-67. Conclusion: Our cohort is the first large series of MCL patients treated essentially with R-HCVAD examining the correlation between PET-CT and outcome in the front-line setting. A positive PET-CT following the completion of therapy identifies patients with an inferior PFS and a trend towards inferior OS. These data do not support the prognostic utility of PET-CT in pre-treatment (no upstaging) and interim treatment settings. This information should be incorporated into the design of future prospective clinical trials. We are currently examining the relationship of novel computer-assisted quantitative FDG-PET/CT measures of total tumor volume and total tumor metabolic burden with clinical outcome in patients with mantle cell lymphoma. Disclosures: No relevant conflicts of interest to declare.