The Prognostic Value of FDG PET/CT Prior to Autologous Stem Cell Transplant in Mantle Cell Lymphoma
Authors: Cohen Jonathon B. , Hall Nathan , Ruppert Amy S. , Jones Jeffrey A. , Porcu Pierluigi , Baiocchi Robert A. , Penza Sam , Benson Don M , Andritsos Leslie A , Flynn Joseph M. , Devine Steven M. , Blum Kristie A 
Published: October 2019

Abstract
Abstract 3113

Background:
Pre-transplantation FDG-PET/CT (PET/CT) has been associated with progression-free survival (PFS) and overall survival (OS) in patients (pts) with relapsed Hodgkin's and diffuse large B-cell lymphoma (Spaepan, Blood.102 :53-59, 2003). However, no data exist regarding the role of PET/CT pre-transplant in pts with mantle cell lymphoma (MCL). We performed a retrospective analysis of pts with MCL and available pre-transplant PET/CT to evaluate the association of pre-transplant PET/CT findings with PFS and OS.

Methods:
PET/CT was reviewed by a single radiologist according to International Harmonization Committee (IHC) criteria with mediastinal blood pool as the referenced background activity and also utilizing liver blood pool. Bone marrow (BM) uptake was not utilized in the PET/CT response assessment. Associations between PET/CT positivity and clinical characteristics were performed using Fisher's Exact and Wilcoxon rank sum tests. PFS curves were constructed from date of transplant until date of relapse or death by the Kaplan-Meier method and evaluated by the log-rank test. Univariable proportional hazards models described the relationship between clinical variables and PFS.

Results:
Twenty-nine pts with PET/CT prior to autologous stem cell transplant were included. Median age was 60 (range 37–73), and 86% were male. Median MIPI was 5.9 (range 4.9–7.0), with 36%, 40%, and 24% of pts classified as low (< 5.7), intermediate (5.7–6.2), or high risk (> 6.2), respectively. At diagnosis, 93% of pts had BM involvement, 56% had splenomegaly, and 27% had bulky adenopathy ≥ 5cm. Sixty-nine percent of pts were induced with RCHOP and methotrexate (RCHOP+M, Damon, JCO 27 :6101–6108); other therapies included RCHOP (n=4), RHyperCVAD (n=2), bortezomib (n=2), and REPOCH (n=1). Sixty-six percent, 21%, and 14% of pts received 2, 3–5, or 6 induction cycles prior to transplant, respectively. Conditioning regimens were BEAM (59%) and BEC (41%) and 90% of pts underwent transplant in first remission. Median time to transplant from diagnosis was 5.4 months (range 3.4–82). With a median follow up of 18 months (range 0.7–43), estimated median PFS is 42 months (95% CI 15–45). There have been 7 relapses (4 RCHOP, 1 RCHOP+M, 1 bortezomib, 1 REPOCH) and 5 deaths (disease progression, n=3, and pneumonia, n=2). Seventeen pts (59%) had a negative PET/CT prior to transplant, with identical results using mediastinal or liver blood pool. In 19, 6, and 4 pts respectively receiving 2, 3–5, and 6 cycles of induction therapy, 58%, 50%, and 75% were PET/CT negative prior to transplant. PET/CT positive pts received RCHOP+M (n=10), RCHOP (n=1), and bortezomib (n=1), Compared to PET/CT negative pts, PET/CT positive pts were younger (median age 55 v. 62, p=0.04) with lower MIPI (p=0.05). There was no significant association of bulky adenopathy (p=0.09), induction with RCHOP+M (p=0.23), or number of induction cycles (p=0.87) with PET/CT findings. 5 pts had a positive pre-transplant BM biopsy, of which 2 were BM negative by PET/CT. BM positivity on pre-transplant PET/CT was observed in 14 pts with only 3 also positive by BM biopsy. Median PFS was 45 months (95% CI 13–45) for PET/CT negative pts and 33 months (95% CI 3–33) in PET/CT positive pts (Figure 1; p=0.03). At this time, 4 of 17 PET/CT negative pts have progressed or died compared to 5 of 12 PET/CT positive pts. Of the 5 deaths experienced thus far, 4 have occurred in PET/CT positive pts. Presence of bulky adenopathy ≥ 5cm was also associated with a worse PFS (p=0.01), but MIPI (p=0.31) and age (p=0.61) were not.

Conclusions:
PET/CT associates with PFS after autologous stem cell transplantation in MCL (p=0.03). However, additional follow-up is needed to see if this association between PET/CT positivity and early relapse in MCL persists. In addition, as the majority of pts had 2 cycles of induction therapy with RCHOP+M, the impact of treatment regimen and number of cycles is difficult to assess in this series. Interestingly, neither age nor MIPI were associated with PFS from transplant, perhaps indicating that clinical characteristics at diagnosis are less important in pts that achieve a complete response by IHC criteria prior to transplant. Prospective investigation with centrally reviewed PET/CT scans compared with standard CT is required to determine the predictive role of pre-transplant PET/CT in MCL.

Disclosures:
No relevant conflicts of interest to declare.