Triple-organ PET/MR can help manage eventual chemo effects in young cancer survivors

Many pediatric cancer survivors initially evidence no functional signs of chemotherapy damage only to develop serious organ problems months or years later. With this common vexation in mind, Stanford University researchers at Lucile Packard Children’s Hospital have piloted a surveillance protocol using PET/MR to find chemo-induced injuries lurking in the brain, heart and bone in a single imaging session.

Their stated hope is that the technique will enable early interventions targeted to preserve the long-term health of these children.

Ashok Theruvath, MD, Heike E. Daldrup-Link, MD, PhD, and colleagues describe their work in a study report published online Aug. 4 in Radiology.

At one to 10 days after a follow-up office visit, 10 post-chemo patients ranging in age from 13 to 19 were scanned with a 3-T PET/MRI scanner outfitted with head, heart and body coils. One hour before the scan, the patients were injected with the radiotracer ¹⁸F-fluorodeoxyglucose (F-FDG).

The researchers imaged the head first, then the hip and knee joints, obtaining images while simultaneously acquiring PET data.

Next they performed the cardiac imaging, with and without gadolinium for contrast.

Three experienced readers blinded to the patients’ charts and histories—a pediatric neuroradiologist, a pediatric cardiac imaging expert and a general pediatric radiologist—looked for tissue abnormalities and, where present, recorded their extent.

The authors report that the triple-organ exams were completed within 90 minutes.

They found abnormalities in eight patients, six of whom had correlating symptoms.

The researchers also found cumulative chemotherapy doses correlated significantly with MRI measures of left ventricular ejection fraction and end-systolic volume but not at all with severity of brain or bone abnormalities.

Further, the cancer survivors who had been treated with methotrexate, which has been tied to eventual cognitive impairment in pediatric leukemia survivors, had significantly lower cerebral blood flow and metabolic activity in key brain areas compared with control subjects.

In their discussion, the authors note the relatively high expense of the F-FDG component of their imaging protocol.

“[I]t can be debated whether our brain, heart and bone imaging could be done with MR imaging only,” they write. “However, we found, in accordance with the findings of other investigators, that ¹⁸F-FDG PET can provide important additional information for the assessment of brain function by allowing detection of abnormal brain metabolism in brain areas that appeared normal on MR images.”

Single-session brain, heart and bone imaging for pediatric cancer survivors “can help in the detection of chemotherapy-induced tissue damage in one session before clinical problems become apparent,” the authors conclude, adding that the technique can “aid in the selection of tailored interventions, and ultimately help to preserve the brain, cardiac and bone health of pediatric cancer survivors.”