Interim 18F-FDG PET SUVmax Reduction Is Superior to Visual Analysis in Predicting Outcome Early in Hodgkin Lymphoma Patients

Abstract

PET performed after 2 cycles of chemotherapy (PET2) allows prediction of outcome in most patients with Hodgkin lymphoma (HL). Visual analysis using a 5-point scale was proposed to assess PET response, but a semiquantitative approach using maximum standardized uptake value (SUVmax) reduction between baseline and interim PET was shown to be superior to the 5-point scale in patients with diffuse large B-cell lymphoma and may also improve the accuracy of interim PET interpretation in HL. To compare the clinical usefulness of both methods in HL patients, we analyzed PET2 according to visual and ΔSUVmax criteria in a retrospective single-center study. From 2007 to 2010, 59 consecutive patients with a first diagnosis of HL were treated with 4-8 cycles of anthracycline-based chemotherapy. Radiotherapy was performed in 19 responding patients with localized disease. PET was done at baseline (PET0) and after 2 cycles of chemotherapy, and treatment was not modified according to the PET2 result. PET2 was interpreted using the 5-point scale (positivity for score 4 or 5). The SUVmax reduction between PET0 and PET2 (ΔSUVmax) was computed for all patients, and patients with a ΔSUVmax greater than 71% were considered good responders. When the 5-point scale was used, 46 patients (78%) achieved a negative PET2 result, 7 of whom failed treatment (negative predictive value, 85%). Forty-nine patients (83%) had a ΔSUVmax greater than 71%, 6 of whom failed treatment (negative predictive value, 88%). The PET2 positive predictive value was significantly better for ΔSUVmax (70%) than for the 5-point scale (46%). When ΔSUVmax was used, 6 (46%) of the 13 PET2-positive patients could be reclassified as good responders. Although visual PET2 positivity was related to a lower 4-y progression-free survival (45%) compared with PET2 negativity (81%, P < 0.002), ΔSUVmax (>71 vs ≤71%) was more accurate for identifying patients with different 4-y progression-free survivals (82% vs. 30%; P < 0.0001). In multivariate analysis using the international prognosis score and ΔSUVmax as covariates, ΔSUVmax remained the unique independent predictor for progression-free survival (P = 0.0001; relative risk, 8.1). Semiquantitative analysis was more accurate than visual analysis based on the 5-point scale to interpret PET2 and predict the outcome of HL patients. These encouraging results warrant further confirmation in larger and prospective series.