Utility of PET imaging in predicting the aggressiveness and histopathology of lymphoma

Abstract

8085 Background: F (18)-fluorodeoxyglucose positron emission tomography (FDG-PET) is widely used in the staging and restaging of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). Few studies have investigated whether the intensity of tumor FDG uptake, measured by standard uptake value (SUV), a semiquantitative measure, could differentiate between indolent and aggressive disease. The clinical utility of SUV in determining the aggressiveness of NHL and HD and in differentiating histopathological subtypes was investigated in the present study. Methods: FDG-PET studies and histopathology of patients with NHL and HD were evaluated retrospectively. Inclusion criteria include PET before any therapy or on relapse of the disease, no diagnosis of diabetes mellitus or other types of cancer and time interval of < 90 days between PET and biopsy. After reviewing the PET scans, the SUV of biopsy site were measured by drawing regions of interest. Mean ± SD of SUV was calculated for HD and various histopathological subgroups of NHL. Results: Fifty-five patients (mean age 58.1 ± 17.2 years, 30 males, 25 females, 13 patients with HD, 42 with NHL, among which 24 with aggressive and 18 with indolent NHL) were included. The mean SUV was 9.9 ± 7.8 for aggressive NHL, 4.1 ± 2.6 for indolent NHL and 11.5 ± 7.3 for HD. Mean SUV was statistically different between aggressive and indolent NHL (p < 0.001) and HD and indolent NHL (p < 0.001), but not between aggressive NHL and HD (p = 0.4). The SUV for the aggressive NHL can be subdivided further as follows: anaplastic (n =3, 15.1 ± 1.7), diffuse large cell (n=19, 9.6 ± 5.3) and follicular grade III (n=2, 8.1 ± 2.2). Indolent NHL included: mantle cell (n=1, 4.3), marginal zone (n=1, 6.3), small cleaved (n=12, 4.2 ± 3.5), low grade follicular (n=4, 3.2 ± 1.4) and small lymphocytic NHL (n=1, 2.3). Conclusions: Our study suggests that FDG- PET can distinguish aggressive from indolent lymphomas. There was a considerable overlap between HD and aggressive NHL.A SUV of seven or less indicates indolent lymphoma. PET could potentially differentiate between different histopathological subgroups of lymphomas. Future studies with greater sample size are warranted. No significant financial relationships to disclose.