QuickScan Reviews in Nuclear Medicine, May 30 2009

Background: FDG-PET/CT imaging after completion of chemotherapy can predict outcome in patients with aggressive non-Hodgkin lymphoma (NHL). Individuals with persistently positive FDG in a tumor site have very poor disease-specific survival. Perhaps of even more clinical importance is the finding that FDG-PET/CT performed after only a few cycles of chemotherapy can identify those patients who will respond favorably to treatment. Objective: To assess the value of mid-treatment FDG-PET/CT results for altering the chemotherapy regimen. Design: Patients with newly diagnosed aggressive B cell NHL were enrolled in this study. All subjects began standard frontline chemotherapy (R-CHOP). FDG-PET/CT was performed following completion of 2 to 3 cycles of therapy. Individuals with a negative FDG-PET/CT result continued the same chemotherapy regimen, whereas those with positive FDG levels in tumor sites were switched to a more aggressive platinum-based regimen including the use of autologous stem cell transplantation (ASCT). Results: 59 subjects were enrolled. Mid-treatment PET images from 33 of these patients revealed positive FDG uptake at 1 tumor sites. Twenty-eight were then switched to a more aggressive regimen with ASCT. With median follow-up of 36 months, the 2-year estimated event-free survival (EFS) was determined to be 75%. In the group of individuals with a negative PET/CT exam at mid-therapy, the 2 year EFS was 89%. International Prognostic Index scores were similar for mid-treatment PET-positive compared to PET-negative subjects. The authors cited their findings in comparison to historical controls who showed mid-treatment FDG positive disease as evidence that PET results after several cycles of chemotherapy may be used to determine the desirability of a more aggressive treatment regimen. Conclusions: The authors conclude: "Further investigations of individualized, risk-adapted strategies based on early metabolic imaging are warranted." Reviewer's Comments: So as the authors correctly state, we cannot draw any definitive conclusions from this study, yet the results reveal the notable promise of adjusting chemotherapy protocols based upon early FDG-PET imaging in patients with newly diagnosed aggressive NHL. There is a related review by Dr Thomas in this issue of an article from J Nucl Med that reinforces the value of PET for determining prognosis based upon response to chemotherapy in NHL.