Positron emission tomography with [18F]fluorodeoxyglucose (PET) performed after two cycles of chemotherapy could predict treatment outcome in Hodgkin lymphoma (HL) (Gallamini et al J.Clin.Oncol. 2007; 25: 3746), but suitable criteria to interpret interim PET remain to be established. A standardized visual analysis using a 5-point scale (5PS) was proposed to assess interim PET response and an international validation study is currently on going. However, standardized uptake value (SUV) may improve interim PET accuracy, and maximum SUV reduction (ΔSUVmax) between baseline and interim PET was shown to be superior to visual analysis in patients with diffuse large B cell lymphoma (Casasnovas et al, Blood 2011; 118: 37). To compare the clinical usefulness of both methods in patients with HL, we analysed interim PET according to visual and SUV criteria in a retrospective single centre study.
From January 2007 to January 2010, 59 consecutive patients with a first diagnosis ofHL were treated in our institution. All patients received 4 to 8 cycles of chemotherapy including ABVD in 50 cases (85%) and BEACOPP in 9 cases. Radiotherapy was performed in 14 responding patients with localized disease. PET was done at baseline (PET0) and after 2 cycles of chemotherapy (PET2) and therapeutic strategy was not modified according to PET2 result. All PET scans were reviewed by SK, ABR and IDC, and interpreted using the 5PS criteria, PET being considered positive when the 5PS score was 4 or 5. SUVmax reduction values between PET0 and PET2 (ΔSUVmaxPET0–2) were available for all patients, and after using the receiver operating characteristics approach, patients with a ΔSUVmaxPET0–2 >71% were considered as good responders after 2 cycles. Progression-free survival (PFS) and freedom from treatment failure (FFTF) were analyzed according to PET results based on 5PS and ΔSUVmaxcriteria. Median follow-up was 39 months (range: 6–62).
Using visual analysis,46 (78%) patients achieved a negative PET2. Seven of them experienced a treatment failure, leading to a PET2 negative predictive value (NPV) of 85%. Fourty nine (83%) patients had a ΔSUVmaxPET0–2 >71% and 6 of them failed to treatment (NPV = 88%). By contrast PET2 positive predictive value (PPV) was significantly better for ΔSUVmax analysis (70%) compared to visual analysis (46%). Using ΔSUVmax analysis, 6 (46%) of the 13 PET2 positive patients could be reclassified as good responder after 2 cycles of chemotherapy. While visual PET2 positivity was associated to a lower 3-year PFS (45%) or FFTF (51%) compared to PET2 negativity (3-year PFS=80%, p=0.001 and 3-year FFTF= 82%, p<0.0035; respectively), ΔSUVmaxPET0–2 (>71% vs≤71%) was more accurate to identify patients with significantly different 3-year PFS (81% vs 30%; p<0.0001; HR = 6.77) and FFTF (85% vs 30%; p<0.0001; HR = 8.79). In multivariate analysis, using the international prognosis score and ΔSUVmaxPET0–2 as covariates, ΔSUVmaxPET0–2 remains the unique independent predictor for PFS (p = 0.0001; RR: 7.9) and FFTF (p = 0.0001; RR: 9.1).
SUVmax reduction between baseline and interim PET was more accurate than visual analysis based on the 5-point scale to predict early outcome of patients treated for HL. ΔSUVmax reduces the excess of positive results related to the PET2 visual interpretation, and appears to be the best method so far to assess early PET response in HL.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.