Frequency and clinical implications of findings on true whole-body 18F-FDG PET in the assessment of breast cancer.

Introduction: In the assessment of breast cancer using 18-F FDG PET/CT, the incremental clinical benefit in performing a true whole-body PET/CT (with a field of view (FOV) from the vertex to the toes) over a limited whole-body PET/CT (with a FOV from the base of skull to the mid-thighs) is uncertain.

Methods: Two hundred and one studies of 120 patients who underwent staging or restaging true whole body 18F-FDG PET/CT for breast cancer were retrospectively identified. Any abnormal hypermetabolic or structural focus outside the limited FOV was recorded and characterised, and referenced with the patient's known disease status and any symptomatology.

Results: A total of 18 (9.0%) studies had FDG avid and/or structural abnormalities detected outside the limited whole-body FOV which were identified as malignant. Seventeen out of 18 (94.4%) were skeletal and of these, 15/17 (88.2%) were located within the lower limbs. In three cases, there were de novo findings but identified in the presence of interval progression of other metastases within the limited whole-body FOV. None of these additional findings is known to have resulted in a change to staging or clinical management.

Conclusion: In the assessment of breast cancer, a true whole-body PET/CT can reveal metastases outside the limited whole-body FOV, but these are unlikely to be encountered in isolation and therefore may have little bearing on clinical stage or management. Ultimately, while the choice of FOV should still be based on the individual patient situation, routine utilisation of the true whole-body FOV in the asymptomatic patient may not be necessary.