Watch for PET/CT to grow as an aid to image-guided biopsies of children

PET/CT can add value to cancer staging and follow-up in pediatric patients. In fact, it may come to play an important role in directing image-guided biopsies of children, according to a study published online Dec. 27 in the American Journal of Roentgenology.

Senior author Bairbre Connolly, MD, of the University of Toronto and colleagues note that PET/CT is increasingly used to evaluate adult oncology patients with the radiotracer FDG, which enables precise localization of high cellular activity. But the question has been largely open as to whether FDG PET/CT can be similarly useful in children, who tend to have higher FDG activity in regions of growth, adenoids, tonsils and bone marrow, among other typical FDG differences.

To find out, the authors reviewed the cases of 45 patients (23 boys, 22 girls; age range, 4 to 17 years) who underwent PET/CT exams and image-guided biopsy within six weeks of the scans, either before or after the biopsy, at the Hospital for Sick Children in Toronto.

Nineteen patients (20 biopsies) had known malignancy, and 26 patients had suspected malignancy.

The results were malignant in 24 cases, benign in 16 and inadequate or normal in seven cases.

Thirty-nine of 47 PET/CT exams had positive results; eight had negative results.

On analysis, the researchers found that 37 of the 47 cases showed concordant results between biopsy and PET in 36 cases.

Discordant results came back in just one case.

“In our study, all histopathologically proven malignancies had abnormal PET results with high [FDG] uptake, unless interval treatment had been administered,” the authors write. “These findings support the valuable role of PET/CT in directing image-guided biopsies in children.”

In their discussion, Connolly et al. further note that, in adults, intraprocedural CT has been recommended to guide biopsy based on previous PET/CT images.

“In the future, multimodality image fusion may further assist in this regard, and even biopsy may be performed with PET/CT guidance,” they conclude, adding that fusion of images is currently possible by use of DICOM-compatible images of volumetric data.

“Going forward, in future biopsies, the choice of site within a lesion or the choice of one lesion over another may be guided by results of PET, when it is available before biopsy.”

The authors acknowledge that their small study’s applicability is limited by its retrospective design and other factors.

They call for prospective studies with larger numbers of subjects in order to more fully evaluate the role of PET/CT in guiding the interventionalist to a biopsy site and to establish specificity and sensitivity.