THE ROLE OF 18F FDG‐PET/CT IN PERIPHERAL T‐CELL LYMPHOMA (PTCL): INITIAL RESULTS OF THE UK NCRI MULTICENTRE PHASE II RANDOMISED CHEMO‐T TRIAL PET/CT SUBSTUDY

Abstract

Introduction: The evidence base for positron emission tomography/ computed tomography (PET/CT) (PET) in PTCL comes from retrospective studies. Herein, we report the initial results of a PET substudy within a prospective trial for patients with previously untreated PTCL. Methods: The UK NCRI phase II randomised multicenter CHEMO-T trial compared the regimens of cyclophosphamide, doxorubicin, vincristine and prednisolone (CHOP) with gemcitabine, cisplatin and methylprednisolone (GEM-P) in previously untreated patients aged ≥18 years with stage I (bulky)-IV disease of the following subtypes: PTCL not otherwise specified (PTCL NOS), angioimmunoblastic T-cell lymphoma (AITL), anaplastic large cell lymphoma (ALCL) ALK negative, enteropathy-associated T-cell lymphoma (EATL) and hepatosplenic gamma delta T-cell lymphoma. In November 2016, the study closed early to recruitment due to an inferior complete response (CR/CRu) rate at end of treatment (EOT) by CT in the GEM-P arm compared to the CHOP arm. (Table Presented) All patients had baseline (BL) and EOT PETs performed in accordance with the study protocol. The primary study endpoint was to compare the CR/CRu rate by contrast-enhanced CT at EOT between arms according to the IWG 1999 criteria. Secondary endpoints included a comparison of EOT response by CT versus PET. All PET scans were centrally reviewed while blinded to the patient's clinical status. The following parameters were assessed at BL and EOT: Deauville score (DS), mean, max and peak standardized uptake values (SUVs) and metabolic tumour volume (MTV). At EOT, a DS of 1-2 by PET was negative, a DS of 3-5 was positive. For patients with biopsy-proven bone marrow (BM) involvement at randomisation, PET at BL was reviewed to assess for BM FDG avidity. In an exploratory analysis, PET scores at BL (DS, max/mean/peak SUVs and MTV) were associated with overall response (ORR) by PET. Results: BL central PET review has been completed for 58 (PTCL NOS n = 23, AITL = 25, ALCL ALK negative n = 10) of the 87 patients accrued at time of study closure. All patients had FDG-avid disease at BL (DS = 3 5.2%, DS = 4 28.6%, DS = 5 67.2%). For patients with BM involvement at BL and an evaluable PET (n = 19), 7 (36.8%) had BM uptake on PET. EOT PET response has been completed for 41/ 87 patients, with DS as follows: 1-2 = 78.1%, 3 = 7.3% and 4-5 = 14.6%. ORR by PET was 80.4% (CR = 56.9%, PR = 23.5%). The proportion of agreement in determination of CR versus PR/SD/ PD between PET and CT is shown in Table 1. MTV at BL was the best predictor of response on EOT PET. Conclusion: All PTCL subtypes evaluated to date were FDG avid at BL. In PTCL, PET does not appear to be a sensitive tool for determination of BM infiltration. In the determination of CR the proportion of agreement between EOT CT and PET was 80.4%. In an exploratory analysis, MTV at BL was the score most associated with ORR by PET. The updated complete analysis (N = 87) including correlation of PET scores at BL and PET response with survival will be presented at the meeting.