Quantitative evaluation of interim positron emission tomography in peripheral T-cell lymphoma.

Background: Interim [F]fluoro-deoxyglucose-positron emission tomography predicts outcome in peripheral T-cell lymphoma (PTCL). We compared two quantitative evaluation methods.

Methods: Interim scans from 43 patients with anaplastic lymphoma kinase-negative PTCL from the 'Positron Emission Tomography-Guided Therapy of Aggressive Non-Hodgkin Lymphomas' trial were re-analyzed by qPET (relating residual lymphoma-related uptake to liver uptake) and ∆SUV (relating interim scan to baseline scan). The endpoint was progression-free survival.

Results: qPET and ∆SUV were closely correlated (Pearson's r = 0.627). Up to the 60 percentile of values ranked by increasing residual activity, the positive predictive value for progression or death increased from 60 to 95%, with stable negative predictive values (NPV) of 60%. Beyond the 60 percentile, the NPV decreased to 40%. qPET ≥ 2 and ∆SUV < 50% identified high-risk populations comprising 41.9% and 39.5% of patients, with 3-year progression-free survival rates of 5.6% (95% confidence interval, 0.8-37.3) and 0%, respectively, as compared to 63.7% (47.4-85.8) and 61.3% (45.1-83.3) in low-risk patients.

Conclusions: qPET and ∆SUV identify large fractions of PTCL patients destined to experience treatment failure. qPET may be preferred because it requires a single PET scan, halving the diagnostic effort.