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Nucl Med Commun. 2013 Apr;34(4):333-9. doi: 10.1097/MNM.0b013e32835f163f.

Frequency and clinical implications of incidental new primary cancers detected on true whole-body 18F-FDG PET/CT studies.

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Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94143, USA.



To determine the frequency of additional primary malignancies in patients undergoing staging/restaging with PET/computed tomography (CT) and to determine the frequency with which these unsuspected findings change clinical management.


This is a retrospective review of 556 patients who had undergone a total of 804 PET/CTs for staging/restaging. Lesions that were at an atypical location for a metastasis from the primary malignancy (indication for the study) and had a maximum standardized uptake value greater than 2.5 were considered suspicious. Suspicious lesions were followed up by a combination of clinical examination, biopsy, and additional and/or follow-up imaging.


Forty-three (7.7%) patients had lesions that were suspicious for a newly discovered primary malignancy that was different from the known/suspected malignancy (indication for study). Eight (1.4% of 556) of these patients had biopsy confirmation of an additional synchronous or metachronous primary malignancy. However, these suspicious lesions changed the clinical management for 18 (3.2% of 556) patients. Patients with early-stage disease (stages 1 and 2) based on the malignancy for which the study was conducted were three times more likely to have these suspicious lesions biopsied, evaluated by clinical examination or by additional immediate imaging than were patients with advanced-stage disease (stages 3 and 4); however, this difference was not statistically significant (P=0.08).


Unsuspected additional primary malignancies are rarely identified in patients undergoing staging/restaging with PET/CT but have the potential to significantly impact clinical management.

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