Predictive value of PET response combined with baseline metabolic tumor volume in peripheral T-cell lymphoma patients

Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of aggressive non-Hodgkin lymphomas with poor outcomes with current therapy. We investigated if response assessed with Positron Emission Tomography/computed tomography (PET/CT) combined with baseline total metabolic tumor volume (TMTV) could detect early relapse/refractory patients.Methods:140 patients with nodal PTCL who underwent baseline PET/CT were selected from 7 European centers. 43 had interim PET (iPET) performed after two cycles (iPET2), 95 after 3 or 4 cycles (iPET3/4) and 96 had end of treatment PET (eotPET). Baseline TMTV was computed with 41% SUVmaxthreshold, and PET response was reported with the Deauville 5-point scale (5-PS).Results:With 43 months median follow-up, the 2-year Progression free survival (PFS) and Overall survival (OS) were 51% and 67%. Positive iPET2 patients (5-PS ≥4) had a significantly worse outcome than those with negative iPET2 (p<0.0001, HR=6.8 for PFS, p<0.0001, HR=6.6 for OS). Value of iPET was also confirmed after 3 or 4 cycles for PFS (p<0.0001) and OS (p<0.0001). The 2-year PFS and OS for iPET3/4 positive (n= 28) and iPET3/4 negative (n= 67) patients were 16% and 32% vs. 75% and 85% respectively. EotPET results also reflected patient outcome. A model combining TMTV and iPET3/4 stratified the population into distinct risk groups: TMTV≤230 cm3and iPET3/4 negative (2-year PFS/OS 79%/85%); TMTV>230cm3and iPET3/4 negative (59%/84%); TMTV≤230cm3and iPET3/4 positive (42%/50%); TMTV>230cm3and iPET3/4 positive (0%/18%).Conclusion:IPET response is predictive of outcome and allows early detection of high-risk PTCL patients. Combining iPET with TMTV improves risk stratification in individual patients.