Positron emission tomography/computed tomography findings during therapy predict outcome in patients with diffuse large B-cell lymphoma treated with chemotherapy alone but not in those who receive consolidation radiation.

To assess the value of mid-therapy positron emission tomography (PET) findings for predicting survival and disease progression in patients with diffuse large B-cell lymphoma, considering type of therapy (chemotherapy with or without radiation therapy).We retrospectively evaluated 294 patients with histologically confirmed diffuse large B-cell lymphoma with respect to age, sex, disease stage, International Prognostic Index score, mid-therapy PET findings (positive or negative), and disease status after therapy and at last follow-up. Overall survival (OS) and progression-free survival (PFS) were compared according to mid-therapy PET findings.Of the 294 patients, 163 (55%) were male, 144 (49%) were age >61 years, 110 (37%) had stage I or II disease, 219 (74%) had International Prognostic Index score ≤2, 216 (73%) received ≥6 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone, and 88 (30%) received consolidation radiation therapy. Five-year PFS and OS rates were associated with mid-therapy PET status: PFS was 78% for those with PET-negative (PET-) disease versus 63% for PET-positive (PET+) disease (P=.024), and OS was 82% for PET- versus 62% for PET+ (P<.002). These associations held true for patients who received chemotherapy only (PFS 71% for PET- vs 52% PET+ [P=.012], OS 78% for PET- and 51% for PET+ [P=.0055]) but not for those who received consolidation radiation therapy (PFS 84% PET- vs 81% PET+ [P=.88]; OS 90% PET- vs 81% PET+ [P=.39]).Mid-therapy PET can predict patient outcome, but the use of consolidation radiation therapy may negate the significance of mid-therapy findings.