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.

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 (_BLPET/CT), CECT and BMB were compared. Response by CECT and PET/CT was correlated with outcomes. _BLPET/CT data were available for 82/84; 98% (80/82) had FDG-avid disease. _BLPET/CT altered disease stage in 43% and identified additional extranodal sites (most frequently bone marrow/bone n = 7) in 25% versus CECT. Concordance of _BLPET/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, _BLPET/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.