Positron emission tomography predicts transplantation outcome

High-dose chemotherapy with hematopoietic stem cell transplantation has become a mainstay of treatment for patients with non-Hodgkin lymphoma or Hodgkin lymphoma who either fail to achieve a complete remission or who have relapsed disease. As investigators analyzed the results of this approach, it quickly became apparent that disease status and chemotherapy sensitivity were powerful prognostic factors (Philip et al, N Engl J Med. 1987;316:1493-1498). More recently, it has been shown that early lymphocyte recovery after stem cell transplantation is strongly associated with improved progression-free survival, though this prognostic factor cannot be assessed prior to transplantation (Porrata et al, Blood. 2001;98:579-585). Positron emission tomography performed either partway through conventional chemotherapy or at the close of therapy has been shown to be predictive of outcome in Hodgkin lymphoma and non-Hodgkin lymphoma (Spaepen et al, J Clin Oncol. 2001;19:414-419).

In this issue, Spaepen and colleagues (page 53) report the results of a retrospective analysis of the predictive value of positron emission tomography performed after salvage therapy prior to stem cell transplantation in patients with non-Hodgkin lymphoma or Hodgkin lymphoma. Of 30 patients with a negative study prior to transplantation, 25 remained in remission while 2 succumbed to treatment-related mortality and 3 had relapsed disease. Of 30 patients with abnormal ¹⁸F-fluorodeoxyglucose (FDG) uptake prior to transplantation, 26 had progressive lymphoma after transplantation. The 4 patients with false-positive results (abnormal uptake but no disease progression) appeared to have had uptake related to either infection (2 cases) or irradiation prior to the study (2 cases).

If these findings are confirmed by larger prospective trials, routine positron emission tomography prior to hematopoietic stem cell transplantation may become the new standard for assessing chemotherapy sensitivity. It will be important for false-positive results to be identified so that patients are not erroneously excluded from transplantation based on an overestimated risk of relapse.