End point



Point of measurement

Overall survival

All patients

Death from any cause

Entry onto trial

Event-free survival


Failure or death from any cause

Entry onto trial

Progression-free survival

All patients

Disease progression or death from NHL

Entry onto trial

Response duration


Time to relapse or progression

First documentation of response

Disease-free survival


Time to relapse

First documentation of response

Time to next treatment

All patients

Time next treatment is required

Trial entry

Cause-specific death

All patients

Death related to NHL


follow-up of just under 2 years. The remaining 20% of patients relapsed in a median of 316 days. All of the 29 patients with positive PET scans at the completion of therapy relapsed at a median of 105 days. A similar study by Mikhaeel reported a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 82% for PET scanning used at the completion of therapy.3 Several other studies have now been reported, with similar results, all suggesting that FDG-PET predicts tumor viability and subsequent relapse in residual masses with 80-90% PPV, after first line and, in some cases, salvage therapy, including ASCT.4-6

A recent retrospective study from Juweid et al. has assessed the use of FDG-PET in combination with the International Workshop criteria (IWC) in patients with aggressive NHL in an attempt to determine whether PET scanning adds increased discrimination in outcome compared with conventional response criteria.7 The study included 54 patients with aggressive NHL, mostly DLBCL who underwent FDG-PET and CT scanning between 1 and 16 weeks after completion of 4-8 cycles of cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP)-based chemotherapy. Responses to therapy were assessed by conventional IWC and by an additional set of criteria which included PET. Based on subsequent risk of relapse, used as a surrogate for the accuracy of each methods of response assessment, IWC plus PET provided a more accurate assessment, in particular because PET was able to identify a subset of patients in PR by IWC who were PET negative, and carried a more favorable prognosis. Further studies are underway at the moment, which will probably further define the value of PET in this situation and it is likely that the IWC will be modified in the near future to integrate data from functional imaging.

Additionally, the use of functional imaging early in the course of therapy is being assessed as a method of response assessment and prediction of subsequent outcome (see the section on prognostic factors).

It is important to emphasize that most present data regarding PET scanning for response assessment relates to aggressive NHL. Few data are available for indolent subtypes of lymphoma.

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