Abstract
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Objectives The aim of the study is to evaluate the role of whole body FDG PET CT compared with conventional contrast enhanced CT in the follow-up of lymphoma patients. To determine the modality more likely to be correct in lesions with discordant findings.
Methods Retrospective review of findings was performed for 411 studies in 106 patients (49 HL and 57 NHL) , age range 9-78 yrs, who underwent PET CT and contrast enhanced CT (CECT) for response evaluation or surveillance during March 2005 - July 2011. Concordance between CECT and PETCT was identified when both procedures identified the same disease sites. Discordant findings were further investigated by using other diagnostic procedures including MRI, tissue diagnosis and or clinical follow-up.
Results Out of 411 studies, complete concordance was seen between PET CT and CECT in 404 studies (98%). 7 studies were found to be discordant in their findings, all PET+/CT- (2/7 false positives, 5/7 true positives). PET CT identified bone/bonemarrow disease in 3/7 studies and upstaged disease in 2/7 patients to stage IV, the remaining patient was already stage IV based on positive bone marrow biopsy. In the 2 PET false positives studies there was no change in management, based on clinical considerations. The contrast CT results were not essential for decision making.
Conclusions PET CT is more accurate for monitoring response to therapy and in diagnosing relapse. In discordant lesions, the PET CT results were found to be more accurate. There were no studies in which contrast CT significantly changed patient management. If the CT studies had not been done, these patients would have avoided the radiation exposure and expense assocociated with the CTs, without any impact on their management. We recommend that contrast CTs should not be routinely done in conjunction with PET-CT in the followup of lymphoma patients