Interim [(18)F]fluorodeoxyglucose positron emission tomography imaging in stage I-II non-bulky Hodgkin lymphoma: would using combined positron emission tomography and computed tomography criteria better predict response than each test alone?

Our objective was to validate the International Harmonization Project (IHP) positron emission tomography (PET) response criteria and correlate with the Deauville criteria and diagnostic computed tomography-based (dCT) lesion size changes. All patients were recruited prospectively to the Cancer and Leukemia Group B (CALGB) 50203 trial for the treatment of stage I-II, non-bulky Hodgkin lymphoma (HL). [(18)F]Fluorodeoxyglucose (FDG) PET and dCT were performed at baseline and after two doxorubicin, vinblastine and gemcitabine (AVG) cycles (PET-2, dCT-2) in 88 patients. IHP and Deauville criteria and percent decrease in the sum of the products of the perpendicular diameters (%SPPD) after two cycles were correlated with progression-free survival (PFS). After a median follow-up of 3.3 years, 23.9% of patients relapsed/progressed (3-year PFS 77%). By IHP, the 2-year PFS was 88% and 54% for PET-2 negative and positive groups, respectively (p = 0.0009). Similar results were obtained for Deauville criteria. In a univariate analysis, PET-2 predicted PFS better than %SPPD, and in a combinatorial analysis, in the PET-2 positive group, a negative dCT-2 increased PFS by 27-35%. However, some confidence intervals were large due to small sample sizes. In conclusion, IHP and Deauville criteria-based interpretation of PET-2 was strongly associated with 2-year PFS. The combined analysis of PET-2 with dCT-2 suggested a better predictive value for PFS compared to either test alone. Further studies are under way to confirm these findings.