Doublet Versus Triplet PET: Is END of Therapy PET Needed IF Interim PET Is Negative in Hodgkin'S or Diffuse Large B CELL Lymphoma?

Introduction: Baseline (PETb) and end of therapy (PETe) FDG PET is standard of care in the management of hodgkin's lymphoma (HL) and diffuse large B cell lymphoma (DLBCL). The role of interim PET (PETi) in HL is well established while its role in DLBCL is not well defined. We evaluated the utility of triPET (PETb, PETi and PETe ) in management of these two lymphomas. Methods: Retrospective review of PET archives revealed a total of 37 pts (HL=22, DLBCL=15). TriPET were acquired per accepted protocol. SUVmax and Deauville scores (DSc) were obtained from five target lesions, the average i.e. composite SUVmax & DSc were computed for each pt. Statistical analyses were performed with the composite maxSUV (cSUV) and Deauville scores (cDSc) (using EXCEL). Following statistics were performed (separately and combined in HL and DLBCL); mean+SD, PPV and NPV for complete response (CR) Vs. progressive disease (PD) on PETi using the following variables 1. cSUV and 2. cDSc and 3. delta change (DELT). Median progression free survival (PFS) was the clinical endpoint for response. Results: The mean PFS in our group was 17 and 15 months in HL and DLBCL respectively. Using cut off thresholds for intP to predict CR at cSUV=80%,. In HL: for cSUV- PPV 67%, NPV 95%; for DELT of cSUV PPV 100%, NPV 95%; for cDSC-PPV 30%, NPV 100%. In DLBCL: for cSUV- PPV 25%, NPV 100%; for DELT of cSUV PPV 33%, NPV 100%; for cDSC- PPV 50%, NPV 100%. Conclusion: The results from our series suggest that PETi has a role not only in HL but in DLBCL as well. Our modest cohort suggests that a negative PETi in DLBCL had a NPV of 100% across cSUV, cDSc and DELT, with regards to CR. Our data also suggests that PETe is not needed if PETi is -ve. While in HL subset, our results concur with results from other groups, this needs to be validated in a larger series. Disclosures No relevant conflicts of interest to declare.