Impact Of Interim Pet On Hodgkin Lymphoma Treatment Outcome And Survival In Clinical Practice.

e20017 Background: FDG avidity above liver on interim PET (PET2) during frontline ABVD is considered a marker of impending treatment failure and an indication to switch to an intensified regimen. However, in clinical practice the utility of PET2 for treatment decisions is less clear. We describe outcomes of patients with positive PET2 who continued treatment with ABVD in the clinical setting. Methods: A retrospective study of all patients with newly diagnosed advanced-stage Hodgkin lymphoma treated with frontline ABVD at Memorial Sloan Kettering Cancer Center between 2008-2017. Eligibility criteria were set to correspond with the RATHL inclusion criteria (stage IIB - IV, or IIA bulky or ≥ 3 involved sites). We identified all PET2 reports indicating suspected residual uptake. All positive PET2 images were then reviewed by a single study radiologist. To increase reproducibility and avoid selection of borderline cases, we defined as PET2 positive only those cases with a lesion-to-liver (mean) SUV ratio ≥ 1.3. We also used a recently published stringent criterion of lesion-to-liver (max) ratio ≥ 1.4 (mPET2+). Progression-free and overall survival (PFS, OS) were calculated from the date of initial treatment until progression or death of any cause. Consolidative radiation was not considered a PFS event, and all progressions were verified by biopsy. Results: We identified 227 patients fitting RATHL inclusion criteria treated with ABVD. Median age was 34, with 25% (58) ≥ 45 years, 12% (26) had an IPS ≥ 4; 28% (64) stage II (5% II-X) and 38% (87) with extranodal involvement. 57 (25%) patients had a PET2 report indicating suspected residual lymphoma (PET2+), however, only 32 (14%) met the more stringent mPET2+ criterion. Most patients with PET2+ continued ABVD (84%, 48), and 9 switched to escBEACOPP (this subset of patients had substantially worse disease and are not the focus of this analysis). 21 (9%) patients received consolidative radiation. With a median follow-up of 47 months (42-54m), PET2+ patients who continued ABVD had a 3yPFS of 70% (58-85%, n = 48); mPET+ had a 3yPFS of 71% (55-92%, n = 24). Overall survival was excellent regardless of PET2 status (5yOS 97%). Conclusions: The outcome of PET2+ patients in this analysis was better than previously reported and the continuation of ABVD was appropriate for most patients. Use of a confirmatory biopsy is important for identifying true progressions. Patients with PET2+ had an excellent OS. Evaluation of the superiority of alternative regimens in PET2+ patients requires an ABVD comparator arm.