The utility and prognostic value of Positron Emission Tomography with Fluorine-18-Fluoro-2-D-Glucose (FDG ? PET) on Patients with Hodgkin and Non-Hodgkin Lymphoma

Background: 18F-FDG-PET is a functional imaging method and widely used for initial diagnosis, staging and response evaluation in the treatment of malignant lymphomas. Although lymphomas are potentially curable malignancies, residual masses after completion of first line treatment are associated with relapses. Conventional morphologic imaging methods such as CT can not distinguish viable tumor from fibrotic-necrotic tissue. 18F-FDG-PET offers an advantage of functional tissue characterization. We evaluated the FDG-PET for initial staging and post treatment evaluation of patients with HL and NHL. We also aimed to assess the prognostic value of FDG-PET in these patients.Patients and Methods: One hundred and five untreated patients with histologically proven malignant lymphoma were included the study. Statistical analysis was performed on 94 of these patients who have at least 12 months follow-up period. FDG-PET was performed on initial staging and after completion of primary chemotherapy and we evaluated these patients retrospectively. Treatment response in FDG-PET was correlated with PFS and OS. Cox regression analyses were performed to test the value of prognostic factors.Results: Ninety-four patients with HL (n=19) and NHL (n=75) (median age:52.5, range 20-80 years) were included the study. All initial PET-CT results were positive for lymphoma involvement. After completion of first line chemotherapy (R-CHOP or CHOP-like regimens for NHL, and ABVD for HL), PET-CT results were became negative in 75 (79.8%) of patients. Only 16% of PET negative patients relapsed and underwent RT or salvage CT ± HDT/ASCR. All PET-positive patients (20.2%) relapsed except for two patients with gastric DLBCL and HL with bone involvement. Median follow-up was 18 months. Estimated 1- and 2-year PFS rates were 88% and 78% for PET negative group, and 33% and 11% for PET positive group (p<0.00001). Estimated 1- and 2-year OS were not significantly different in the two groups (p=0.82). Multivariate Cox regression analysis showed that post-treatment PET was an independent prognostic factor for PFS. In patients with DLBCL (n=50), post-treatment PET negativity was associated with significant PFS advantage (p<0.0001) and was an independent prognostic factor.Conclusion: We concluded that post treatment FDG-PET is an accurate and independent predictor of PFS. True and early diagnosis of post treatment residual disease can be helpful for selection of the patients who require aggressive treatment modalities such as HDT/ASCR.Key words: Lymphoma, FDG-PET, prognosis.