The role of systemic and cranial 18Fluorodeoxyglucose positron emission tomography (FDG PET) in primary central nervous system lymphoma (PCNSL)

Abstract

1535 Background: The utility of body and brain FDG PET in staging and management of PCNSL is unknown. Methods: We performed a retrospective study of 166 PCNSL pts at Memorial Sloan-Kettering Cancer Center between January 2000 and August 2005. Pts. who underwent PET imaging were identified using the electronic medical record. PET reports and clinical data were reviewed to determine the reason for the study and impact on management. Results: 61 (37%) pts had ≥1 PET scans. Of 93 studies, 58 were body scans and 35 were brain scans. 72% (42/58) of body PET were done for systemic staging at diagnosis and 28% (16/58) at relapse. 19% (8/42) of scans done for initial staging had suspicious systemic foci. Lymphoma was found in 3 (37.5%), adrenal adenoma in 1 (12.5%), duodenal adenocarcinoma in 1 (12.5%) and non-diagnostic tissue in 1 (12.5%); biopsy was not pursued in 2 (25%). 31% (5/16) of scans done at relapse were abnormal. In 3 (19%) of these, biopsy revealed lymphoma; in 2 (12.5%), biopsy was not pursued. In 8% (4/50) of pts (SUV 12.8, 14.3, 22, 30.5), PET was the only study to demonstrate systemic lymphoma. 2 other pts found to have systemic disease had suspicious findings on conventional imaging in addition to positive body PET (SUV 3.8, 4.1). 43% (15/35) of brain PET were done at diagnosis and 57% (20/35) were done to evaluate residual MRI abnormalities after treatment. 14 brain PET at diagnosis were positive; SUV reported in 7 of these pts ranged from 7.5 to 26.8. The pt with a negative PET was receiving steroids. 10 brain PET done after treatment showed residual tumor and affected interpretation of MRI response. SUV reported in 7 of these pts. ranged from 8.1 to 29. Conclusions: Body PET imaging appears to be a sensitive tool for the detection of occult systemic lymphoma that may be missed with other diagnostics. While Brain PET at initial diagnosis did not yield incremental information, it may be useful in the interpretation of persistent MRI abnormalities after treatment. No significant financial relationships to disclose.