Interim Positron Emission Tomography (iPET) Assessed Using Deauville Score for Patients with Follicular Lymphoma Receiving First-Line Chemoimmunotherapy

Background: While most patients (pts) with follicular lymphoma (FL) have excellent outcomes with frontline chemoimmunotherapy (CIT), a subset of pts will experience early progression, which is associated with inferior survival. Earlier identification of high-risk FL pts could allow for intervention with novel treatments to forestall early progression. Current prognostic tools are imperfect, particularly for pts receiving bendamustine-based regimens, and novel biomarkers are needed. In Hodgkin lymphoma, interim positron emission tomography (iPET) evaluated based on Deauville score (DS) is highly prognostic and is used to guide response-adapted therapy. The prognostic value of iPET using DS has not yet been assessed in a large population of FL pts receiving frontline CIT. We hypothesized that iPET would predict progression-free survival (PFS) in this population which could support PET-guided treatment approaches. Methods: We retrospectively identified pts with a diagnosis of FL (grade 1-3B) who initiated frontline CIT at Dana-Farber Cancer Institute from 1/2005-3/2019 and underwent an iPET after 2-4 cycles of CIT. Pts who received radiation (XRT) prior to CIT were included. Baseline, interim, and (when available) end-of-treatment (EOT) PET scans were reviewed by a nuclear medicine radiologist in a blinded fashion and assigned a DS of 1-5. Results: 118 pts were identified. The median age was 55 (range 26-82). 73 pts (62%) had grade 1-2 FL, 17 pts (14%) grade 3A, 15 pts (13%) grade 3B, 12 pts (10%) grade 3 NOS, and 1 pt (1%) grade not reported. FLIPI score was low for 32%, intermediate for 42% and high for 26%. In total, 5 pts (4%) received XRT before CIT. The most common CIT regimens were RCHOP (54%) and BR (42%) (Table 1). 107 pts (91%) received 6 cycles of CIT and 4 pts (3%) received 8 cycles, while 7 pts (6%) discontinued CIT after 4-5 cycles due to cytopenias (4), heart failure (1), infection (1), or pt decision (1). 88% of iPETs were performed after 3 cycles. iPET DS was 1 for 18%, 2 for 57%, 3 for 13%, 4 for 9%, and 5 for 3%. EOT PET was available for review for 112 pts (95%) and demonstrated DS of 1 for 32%, 2 for 56%, 3 for 3%, 4 for 4%, and 5 for 5%. After CIT, 29 pts (25%) received a median of 9 doses (range 1-13) of rituximab maintenance (RM) and 2 pts (2%) received consolidative XRT. With a median follow-up of 54 months (range 5-186), the 4-year (yr) PFS and overall survival (OS) for the entire cohort were 69% (95% CI 58-77%) and 94% (95% CI 87-98