About 35 children in the Netherlands are found to have a tumor in the kidney each year. Most of the children have a Wilms tumor. Thanks in part to international cooperation and research, much progress has already been made and 9 out of 10 children are cured. Because the odds of having a Wilms tumor are so high, all children with kidney cancer receive the standard treatment for Wilms tumor. That is treatment with chemotherapy for 4 to 6 weeks. Then the surgeon removes the tumor during surgery. If it is a Wilms tumor, it has been reduced in size by the chemotherapy. In the case of a non-Wilms tumor, the chemotherapy is not always effective and in some cases would not have been necessary.
Van der Beek: 'Distinguishing Wilms tumors from non-Wilms tumors is currently only possible by removing a small piece of the tumor for examination under the microscope. Only when the pediatric oncologist suspects a non-Wilms tumor a biopsy is taken under anesthesia using ultrasound through the skin. This, in fact, carries risks. In some cases, additional radiation therapy is required after the biopsy is taken. Therefore, a less invasive way, such as through MRI scans, to determine the type of kidney tumor would offer many advantages. Including knowing in advance whether chemotherapy is effective or not.'
Collaborative comparison
Van der Beek studied how to distinguish between Wilms tumors and non-Wilms tumors based on MRI scans. For this, she collaborated with several departments at the Máxima: Matthijs Fitski, technical physician from the Wijnen group, Prof. Dr. Marry van den Heuvel, pediatric oncologist and research group leader, and the Pediatric Oncology Lab. And pediatric radiologist Dr. Annemieke Littooij from the Wilhelmina Children's Hospital (WKZ) of UMC Utrecht.
Using a special technique of the MRI scanner, Van der Beek calculated how fast water molecules move in kidney tissue and tumors. That technique is called diffusion-weighted imaging, DWI for short. 'Tumor cells are more densely connected than normal cells. As a result, water molecules move more slowly. This degree of cell density allows us to distinguish different tumor cell types. As a matter of fact, the speed of movement of water molecules seems to differ by subtype.'
A personalized "cutting guide" was used to determine the (sub)type of tumor cells very precisely. This 3D printed mold helped Van der Beek compare the different subtypes visible under the microscope with the MRI scan. This allowed her to make DWI measurements that were directly related to a specific part of the kidney tumor.
The results of the feasibility study previously were published in Pediatric Oncology. Results of the follow-up study will appear soon. For this, biopsies and scans from 54 children under treatment at Máxima were examined. Both studies were made possible thanks to funding from KiKa.
Next steps
'The results from this study are promising. And I already take the measurements into account in my considerations in some cases,' says pediatric radiologist Littooij. However, to include the DWI measurement method in the treatment plan requires larger-scale, international follow-up research. 'With this thesis, a nice foundation has been formed for these possible future studies.'
Van der Beek will receive her doctorate from Utrecht University on Tuesday, May 28. Her dissertation is titled Towards Personalized Discrimination of Kidney Tumors in Children based on Imaging with Magnetic Resonance. Her promoters and supervisors are Prof. Dr. Jeroen Hendrikse, Prof. Dr. Marry van den Heuvel-Eibrink, Prof. Dr. Ronald de Krijger and Dr. Annemieke Littooij.