Value of PET restaging after chemotherapy for non-Hodgkin’s lymphoma: Implications for consolidation radiotherapy

Purpose/Objective: Patients treated for non-Hodgkin’s Lymphoma (NHL) frequently are restaged for response using positron emission tomography (PET) scanning. This study investigates the role of subsequent consolidation radiation therapy (CRT) based on PET response to chemotherapy. Materials/Methods: An IRB-approved database was queried for patients who underwent PET scans after chemotherapy for NHL between 1995 and 2004; 77 patients were identified. To determine benefit of CRT, overall survival and local control were assessed with median follow-up of 39.8 months (range, 2–125 months). Results: Median age of patients was 53 (range, 18–82 years). Multivariate analysis adjusted for age, indolent vs. aggressive histology, and time from chemotherapy to PET revealed PET positive scans (RR = 30.5; 95%CI = 5.9, 156.4), lack of RT (RR = 5.25; 95%CI = 1.26, 21.79), and Stage III/IV presentation (RR = 4.35; 95%CI = 1.03, 20) predicted increased likelihood of recurrence. Patients with positive PET scans after chemotherapy had significantly higher risk of relapse than those with negative scans (58.1% vs. 15.2%; p < 0.0001), although not everyone with positive scans recurred. Patients with positive PET scans receiving RT were not protected from relapse (63.2% relapse with RT, 50% relapse without RT; p = 0.71); in fact, over half the relapses in patients receiving RT for persistently positive PET scans were in-field. Crude 2 year OS was significantly different between PET positive and PET negative cohorts ( p < 0.01). Conclusions: While RT may control relapse in PET negative patients, NHL patients who remain PET positive after chemotherapy are not well managed by RT alone.