SUV Max Reduction Criteria of Interim Positron Emission Tomography Improves Prognostic Value in Diffuse Large B-Cell Lymphoma: A Single-Center Retrospective Review
Authors: Okamoto Yusuke , Ochi Shinichi , Nagayama Takashi , Nabe Shogo , Sakai Kazuya , Muranushi Hiroyuki , Sugiura Hiroyuki , Okada Kazuya , Sato Aki , Sato Takayuki , Maeda Takeshi , Onishi Tatsuhito , Ueda Yasunori 
Published: October 2019

Abstract
Background: A consensus is yet to be reached on therole of interim fluorine-18 fluorodeoxyglucose (18F-FDG) position emission tomography-computed tomography (PET-CT) for prognosis in diffuse large B-cell lymphoma (DLBCL), but it has been recently reported that maximum standardized uptake value (SUV max) reduction between baseline and midtherapy may be a better predictor of overall survival (OS) and event free survival (EFS).
Patients and Method: 456 patients were newly diagnosed with DLBCL in our institute between February 2007 and January 2013. Primary central nervous system lymphoma or primary effusion lymphoma patients were excluded from this study. All patients who were not perfomed PET were also excluded. In order to determine the predictive value of interim PET-CT and SUV max reduction criteria on OS and EFS for patients with DLBCL, we retrospectively analyzed the PET-CT and SUV max data of 104 first-line DLBCL patients treated with 6 to 8 courses of R-CHOP or R-THPCOP therapy.
PET-CT was performed at diagnosis (baseline), and after 2 to 4 courses (interim PET). Interim PET was scheduled two weeks after the second to fourth cycle of immunochemotherapy. A visual analysis of interim PET was done with the use of the Deauville criteria, and an analysis of the SUV max reduction criteria was calculated by [(SUV max reduction from baseline to interim PET)/SUV max at baseline]. For each PET image, the tumor with the most intense 18F-FDG uptake was identified among all foci with the use of a graded color scale. The hottest volumetric region was determined, and the SUV max was calculated. To assess the SUV max, the hottest tumor in any region or organ on interim PET was used for comparison, even if its location differed from the initial hottest tumor in baseline PET.
Survival curves were estimated with Kaplan–Meier analysis and compared using the log-rank test.
Results: One hundred and four patients were enrolled in this study, and their characteristics are detailed in Table 1. With a median follow-up of 38.5 months, the two-year overall survival and EFS were 83.3% and 73.6%. The results forinterim PET were 66.3% (69/104) negative and 33.7% (35/104) positive, respectively.
Interim PET negative versus positive two-year OS was 85.0% (95%CI 0.739-0.917) versus 79.9% (95%CI 0.624-0.899) (P value 0.58), and the two-year EFS was 77.7% (95%CI 0.658-0.860) versus 65.7% (0.476-0.789) (P value 0.24), respectively (Figure 1).
The SUV max cutoff values 66% estimated by receiver-operating-characteristic (ROC) analysis to distinguish treatment response were similar to other independent cohort studies at 2 to 4 cycles of induction treatment, and this threshold was chosen to analyze our series.
For SUV max data, the two-year OS was 84.4% (95%CI 0.750-0.904) for a SUV max reduction ≥66.0% compared with 75.0% (95%CI 0.408-0.912) for a reduction of <66.0% (P value 0.02). The two-year EFS for the former was 75.7% (95%CI 0.654-0.833) compared with 58.3% (95%CI 0.270-0.801) for the latter (P value 0.03) (Figure 2). Baseline characteristics according to SUV max reduction criteria [SUV max≥66%(n=92),and SUV max<66%(n=12)] are summarized in Table 1.
Conclusions: Analysis of the data in our study was unable to demonstrate the predictive value of interim PET for OS and EFS, but SUV max reduction criteria may improve the prognostic value of interim PET. However, the 66% cutoff value must be validated in a larger-scale prospective trial, and further investigation and the standardization of SUV max reduction criteria are needed.

Disclosures
No relevant conflicts of interest to declare.