The role of PET/CT in peripheral T‐cell lymphoma: Results from the PET/CT substudy of the UK NCRI phase 2 CHEMO‐T trial

Summary The UK National Cancer Research Institute (NCRI) phase 2 randomised CHOP versus GEM‐P in previously untreated patients with peripheral T‐cell lymphoma (CHEMO‐T) trial compared the regimens of cyclophosphamide, doxorubicin, vincristine and prednisolone (CHOP) and gemcitabine, cisplatin and methylprednisolone (GEM‐P) in treatment‐naïve patients with peripheral T‐cell lymphoma (PTCL). Evaluation of the role of positron emission tomography/computed tomography (PET/CT) was a key secondary end‐point. All patients required PET/CT, contrast‐enhanced CT (CECT) and bone marrow biopsy (BMB) at enrolment and end of treatment (EOT). Baseline (BL) data for PET/CT ( BL PET/CT), CECT and BMB were compared. Response by CECT and PET/CT was correlated with outcomes. BL PET/CT data were available for 82/84; 98% (80/82) had FDG‐avid disease. BL PET/CT altered disease stage in 43% and identified additional extranodal sites (most frequently bone marrow/bone n = 7) in 25% versus CECT. Concordance of BL PET/CT with BMB for marrow involvement was 72.6%, with discordant results for n = 20. Ten patients with biopsy‐proven marrow infiltration had a PET/CT‐negative marrow. However, BL PET/CT detected marrow involvement in patients with a negative BMB ( n = 10), predominantly cases with focal uptake (7/10). At EOT, a negative PET/CT (vs. positive) was associated with superior 2‐year progression‐free survival (PFS) of 55% (95% CI: 38%–70%) versus 29% (95% CI: 12%–48%) [HR 0.45 (95% CI: 0.23–0.88), p = 0.021], respectively, which remained independently prognostic. Our findings indicate that PET/CT should be incorporated as a standard of care in the management of PTCL.