PET for staging in rhabdomyosarcoma: an evaluation of PET as an adjunct to current staging tools.

Background: Complete staging of rhabdomyosarcoma is critical to deliver appropriate therapy. We evaluated the role of F-fluorodeoxyglucose positron emission tomography (PET) in the staging of patients with rhabdomyosarcoma.

Methods: Twenty-four patients with rhabdomyosarcoma had a PET scan during staging evaluation, before or within 13 days of initiation of therapy. PET was compared with computed tomography (CT), magnetic resonance imaging (MRI), bone scan, and pathology.

Results: Ninety-six sites were evaluated. All patients had positive PET scans at the primary site. Thirty-one PET positive sites at primary, regional, or distant sites were biopsied. Pathology in all 31 confirmed disease. Standardized uptake value for the primary site at diagnosis ranged from 2.4 to 12.7 (mean 6.4). At 23 sites, CT or MRI was equivocal for the detection of regional or distant spread. In these cases, a negative PET helped to exclude disease in 21 of 23 patients. PET failed to capture sites of disease visualized by CT, MRI, or bone scan at 10 sites. When comparing PET with the final clinical determination of disease extent, PET was 77% sensitive and 95% specific.

Conclusions: These preliminary data indicate that PET is a useful adjunct in staging rhabdomyosarcoma. A prospective study of PET for staging of rhabdomyosarcoma is warranted.