Brain cancers are difficult to treat, and it can be hard to predict whether a therapy will be effective.

When the patient is a child, it's even more important to predict the potential effectiveness of a drug before beginning treatment.

In this first ever molecular drug-imaging study in children, researchers in The Netherlands used whole-body positron emission tomography/computed tomography (PET/CT) scans to determine whether bevacizumab (Avastin) treatment of diffuse intrinsic pontine glioma (DIPG) in children is likely to be effective.

The study is featured in the May 2017 issue of The Journal of Nuclear Medicine.

"Children with DIPG have a very poor prognosis, with less than 10 percent of the patients surviving two years from diagnosis," explains Guus A. van Dongen, PhD, of VU University, Medical Center, Amsterdam, The Netherlands. "These tumours are resistant to all kinds of therapies. Chemotherapy, as well as new targeted therapies, may not reach the tumour due to the location within the brainstem."

For the study, researchers investigated whether bevacizumab can reach the tumour in children with DIPG by measuring the tumour uptake of zirconium-89 (Zr-89)-labeled bevacizumab with PET.

In addition, they evaluated the safety of the procedure and determined the optimal timing of imaging.

Two weeks after completing radiotherapy, seven patients (age range: 6-17) were given whole-body PET/CT scans performed at 1, 72 and 144 hours post-injection. The optimal moment of scanning was found to be 144 hours post-injection. The patients also underwent contrast (gadolinium)-enhanced MRI.

"The results showed that indeed there is considerable heterogeneity in uptake of Zr-89-labeled bevacizumab among patients and within tumours," Van Dongen points out. "This non-invasive in vivo quantification of drug distribution and tumour uptake may help to predict therapeutic potential, as well as toxicity, and could help develop strategies for improving drug delivery to tumours."

Van Dongen adds, "Children with brain tumours and other solid cancers are particularly likely to benefit from molecular drug imaging, as drugs without therapeutic effect--based on a lack of drug-uptake in the tumour--may cause life-long side effects. Molecular drug imaging will open avenues for administering the right drug to the right patient at the most appropriate stage of the disease."