33 PET

12% downstaged 1 false negative 9% upstaged

No changes in treatment based on PET

Moog et al.2


extranodal Identified 24 lesions not identified by CIM 1 false positive Change of stage in 13

Hueltenschmidt et al.23 HL

25 PET

28% downstaged 12% upstaged Accuracy 96% PET 56% CIM

Delbeke et al.24


45 PET

16% stage change 13% Treatment change CIM

7% stage change Accuracy 91% PET

PET and CIM are complementary

84% CIM

best used as a complementary study in evaluating bone marrow involvement, ideally with follow-up biopsy of any focal areas of uptake in the setting of a negative iliac crest biopsy.

A recurring difficulty in addressing the question of FDG-PET accuracy in staging is the lack of a clear gold standard. In most cases, systematic biopsy of questionable lesions is impractical, and therefore the true result is often defined by the clinical scenario or follow-up. In spite of this limitation, however, studies have repeatedly shown improved staging information with the addition of FDG-PET.

In summary, FDG-PET scanning at initial staging can add valuable information for the clinician. First, a pretreatment FDG-PET scan documents the FDG avidity of a patient's lymphoma, confirming the utility of this modality in follow-up. In addition, PET can refine staging results of anatomic imaging by upstaging through detection of small lesions or diffuse organ involvement. Alternatively, PET may identify patients with a lower stage than suggested by anatomic imaging. However, it is clear that FDG-PET can in some cases show both false-positive and false-negative results. Therefore, discrepancies in staging must be interpreted carefully. In cases of uncertainty, questionable lesions should be biopsied if possible, particularly in cases in which treatment would be altered.

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