Clinical impact of "true whole-body" (18)F-FDG PET/CT: lesion frequency and added benefit in distal lower extremities.

OBJECTIVES

The purpose of this study was to evaluate the lesion frequency and incremental added benefit with "true whole-body" (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) of distal lower extremities. We compared this field of view with the typical whole-body view, from head to upper thighs, in numerous patients with known or suspected malignancy.

METHODS

True whole-body (18)F-FDG PET/CT, from the top of the head to the bottom of the feet, was performed on 4574 consecutively registered patients with known or suspected malignancy. Using a variable sampling method, the PET images of head and torso were acquired for 90 s per bed position, and the images of lower extremities were acquired for 30 s per position, thus requiring between 22 and 24 min of emission scanning per patient. A log was maintained to record cases of abnormal findings in distal lower extremities outside the typical whole-body field of view. Suspected malignant lesions in distal lower extremities were verified by correlation with pathological findings and clinical follow-up.

RESULTS

Abnormal findings in distal lower extremities were found in 647 (14.1 %; 95 % CI 13.1-15.2 %) of 4574 examinations. Increased FDG uptake was found in 559 examinations (12.2 %; 95 % CI 11.3-13.2 %). Lesions appeared malignant or equivocal in 67 examinations (1.5 %; 95 % CI 1.1-1.8 %) on the PET images. In 42 (0.9 %; 95 % CI 0.6-1.2 %) of 4574 examinations, these lesions were pathologically or clinically proven to be malignant. Detection of these malignancies resulted in changing clinical management in 21 (50 %) of 42 examinations. Definitive benign lesions were found in 492 examinations (10.7 %; 95 % CI 9.9-11.7 %) on the PET images. Abnormal findings were noted in 90 examinations (2.0 %; 95 % CI 1.6-2.4 %) consisting of 88 benign and 2 malignancies on the CT images alone.

CONCLUSION

True whole-body (18)F-FDG PET/CT was not of high yield and appears to offer little additional benefit, as to detection of additional metastases and involvement, but it may affect clinical management in patients with known or suspected malignancy.