Interim thymus and activation regulated chemokine versus interim 18 F-fluorodeoxyglucose positron-emission tomography in classical Hodgkin lymphoma response evaluation

Abstract

Serum thymus and activation regulated chemokine (TARC) levels reflect classical Hodgkin lymphoma (cHL) disease activity and correspond with treatment response. We compared mid-treatment interim TARC (iTARC) with interim ¹⁸ F-fluorodeoxyglucose positron-emission tomography (iPET) imaging to predict modified progression-free survival (mPFS) in a group of 95 patients with cHL. High iTARC levels were found in nine and positive iPET in 17 patients. The positive predictive value (PPV) of iTARC for a 5-year mPFS event was 88% compared to 47% for iPET. The negative predictive value was comparable at 86% for iTARC and 85% for iPET. Serum iTARC levels more accurately reflect treatment response with a higher PPV compared to iPET.

Figure 1

TARC and FDG‐PET results during and after treatment. (A) Dynamics of TARC before treatment, after one cycle of chemotherapy, at mid‐treatment and at end‐treatment. TARC levels were analysed using a sandwich enzyme‐linked immunosorbent assay (R&D systems). The cut‐off for TARC positivity at the mid‐treatment time point was 1000 pg/ml as previously defined (Plattel et al., 2012). Patients achieving a complete response without experiencing a relapse are displayed in black. Patients with refractory disease or patients experiencing a relapse are displayed in red. (B) TARC levels at mid‐treatment compared to mid‐treatment FDG‐PET Deauville score. FDG‐PET images were reconstructed according to the European Association of Nuclear Medicine criteria. All FDG‐PET scans were re‐analysed and visually re‐assessed according to the Lugano classification, which incorporates the Deauville 5‐point scale. A Deauville Score ≥4 was considered FDG‐PET positive. (C) TARC levels at end‐treatment compared to end‐treatment FDG‐PET Deauville Score. (D) Modified progression‐free survival (mPFS, see methods for definition) according to mid‐treatment FDG‐PET result. FDG‐PET negativity was defined as Deauville Score ≤3 and FDG‐PET positivity was defined as Deauville Score of 4 or 5. (E) mPFS according to mid‐treatment TARC result. TARC negativity was defined as TARC below the cut‐off of 1000 pg/ml. (F) mPFS according to combined FDG‐PET and TARC result. iTARC negativity generally correlated with favourable outcome, whereas iTARC positivity correlated with adverse outcome irrespective of the iPET result. Survival analyses were performed using the method of Kaplan and Meier and the log‐rank test was used to assess significance.