The Role of An Early Interim ¹⁸ F-FDG PET/CT for Prediction of Outcomes of Patients with Peripheral T Cell Lymphoma

Background Recent studies have demonstrated that positron emission tomography (PET) performed after one to four cycles of multiagent chemotherapy predicts therapeutic outcome in lymphomas which are mainly diffuse large B cell lymphoma and Hodgkin’s lymphoma. However, interim 2-[18F] fluoro-2-deoxy-D-glucose (FDG) PET/CT has not yet been discussed in peripheral T cell lymphoma. In this study, we investigated the role of an interim ¹⁸ F-FDG PET/CT for the prediction of the progression free survival (PFS) and overall survival (OS) in peripheral T cell lymphoma.

Patients and methods We retrospectively analyzed the medical records of thirty-three patients with newly diagnosed, initially FDG-avid peripheral T cell lymphoma between 2004 and 2007 (median age of 44 years, 18 peripheral T cell lymphoma, unspecified, 9 anaplastic large cell lymphoma, 6 angioimmunoblastic T cell lymphoma) who underwent ¹⁸F-FDG PET/CT after one to four cycles of chemotherapy (interim scan). The maximal response to initial therapy was evaluated using conventional methods. Interim FDG-PET/CT results were correlated to the PFS and OS using Kaplan-Meier survival analysis. Cox regression analyses were performed for independence of prognostic factors.

Results The median follow up was 23 months (range, 2–52 months). In the initial therapy, 25 patients achieved CR, 5 patients showed progress and 3 patients died. Interim FDG-PET/CT was negative in 17 patients, positive in 9, and 7 patients showed minimal residual uptake (MRU). The CR rate of initial therapy was 100%, 85% (6/7) and 22% (2/9) in the FDG negative, MRU and positive group, respectively. The estimated 2 year PFS was 88.2% for the negative group, 38.3% for the MRU group, and 0% (median survival of 5.6 months) for the positive group. The log rank test showed strong associations between interim FDG-PET/CT results and PFS (P =0.001) and OS (P <0.001). Also, univariate and multivariate analyses showed that the interim FDG-PET/CT was the only independent factor to predict outcomes among known prognostic factors such as age, elevated lactate dehydrogenase, the number of extranodal disease, stage, performance status (p=0.007).

Conclusion Interim FDG PET/CT is an excellent and independent predictor of outcomes of patients with peripheral T cell lymphoma and is suggested to be a useful tool to modify the therapy.