Towards highly conformal flank irradiation using new flank target volumes in pediatric renal tumors

According to International Society of Pediatric Oncology – Renal Tumor Study Group (SIOP-RTSG) guidelines, children with a renal tumor are treated with upfront chemotherapy followed by tumor-nephrectomy. Around 20% of patients receive postoperative flank irradiation to improve locoregional control. We developed an international consensus guideline for highly conformal flank target volume delineation and revaluated the role of surgical clips for optimizing treatment planning. Moreover, an international multicenter delineation exercise showed significant delineation variation between clinicians, which caused major underestimation of a gold standard in the majority of clinicians. In addition, our dosimetric analysis showed that highly conformal flank irradiation could potentially reduce the risk of diabetes mellitus, functional asplenia, cardiac disease and breast cancer in 60% of the cases. Finally, we obtained first evidence of excellent locoregional control in pediatric renal tumors treated with highly conformal flank irradiation. In the future, SIOP-RTSG multicenter prospective study with mandatory central review will be launched to assess oncological safety and clinical benefit of modern radiotherapy techniques for flank irradiation.