![]() ![]() 4Īn important, albeit preliminary observation from this study, was that most patients with a positive end-of-treatment (EOT) F-fluorodeoxyglucose-positron-emission tomography (FDG-PET) scan achieved durable remissions without further therapy, calling into question the positive predictive value (PPV) of EOT FDG-PET following DA-EPOCH-R. 18 15 In an effort to reduce mediastinal radiotherapy in PMBCL, we conducted a prospective study of DA-EPOCH-R based on hypothesis-generating evidence that dose-intensive regimens may be more effective and showed DA-EPOCH-R obviated the need for radiotherapy in most patients. 10 8 6 It is well documented, however, that mediastinal radiotherapy is associated with significant late toxicity including premature death due to cardiovascular complications and second malignancies, 14 11 which has led to efforts to minimize its use in mediastinal lymphomas. 8 3 R-CHOP is commonly used to treat PMBCL but retrospective studies indicate that this therapy alone is inadequate for many patients, 9 resulting in the frequent use of consolidative mediastinal radiotherapy, as part of combined modality treatment. 2 1 As such, it primarily presents as a bulky mediastinal mass in adolescents and young adults and is more common in females. Primary mediastinal B-cell lymphoma (PMBCL) is a subtype of diffuse large B-cell lymphoma that is clinically and biologically related to nodular sclerosis Hodgkin lymphoma (nsHL). Serial PET imaging distinguished end-of-treatment PET positive patients without treatment failure, thereby reducing unnecessary radiotherapy by 80%, and should be considered in all patients with an initial positive PET following dose-adjusted-EPOCH-R ( identifier 00001337). Among patients with a positive end-of-treatment PET, only 5/25 (20%) had treatment-failure. Virtually all patients with a negative end-of-treatment PET following dose-adjusted-EPOCH-R achieved durable remissions and should not receive radiotherapy. ![]() Among 6 treatment failures, the median end-of-treatment SUV max was 15.4 (range, 1.9-21.3), and 4 achieved long-term remission with salvage therapy. Linear regression analysis of serial scans showed a significant decrease in SUV max in positive end-of-treatment PET non-progressors compared to an increase in treatment failures. Among 25 (31%) patients with a positive (Deauville 4-5) end-of-treatment PET, there were 5 (20%) treatment failures (8-year event-free and overall survival of 71.1% and 84.3%). End-of-treatment PET was negative (Deauville 1-3) in 55 (69%) patients with one treatment failure (8-year event-free and overall survival of 96.0% and 97.7%). One nuclear medicine physician from each institution blindly reviewed all scans from their respective institution. End-of-treatment PET was performed in 80 patients, of whom 57 received 144 serial scans. Ninety-three patients received dose-adjusted-EPOCH-R without radiotherapy. To define the role of PET in primary mediastinal B-cell lymphoma following dose-adjusted-EPOCH-R, we extended enrollment and follow up on our published phase II trial and independent series. End-of-treatment PET, however, does not accurately identify patients at risk of treatment failure, thereby confounding clinical decision making. Dose-adjusted-EPOCH-R obviates the need for radiotherapy in most patients with primary mediastinal B-cell lymphoma. ![]()
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