Hina Saeed MD, Presenter: Nothing to Disclose

Selim Yusuf Firat MD, Abstract Co-Author: Nothing to Disclose

Douglas Prah, Abstract Co-Author: Nothing to Disclose

Purpose/Objective(s):Advances in multimodality treatment have significantly improved the survival rates of patients with Wilm’s tumor. Per Wright et al. the current 8-year survival rate for most patients who have favorable-histology tumors is 80-98%. Standard fields used for flank irradiation can detrimentally affect the growth of the spine (decrease in sitting height and modest decrease in standing height). These effects are more pronounced the younger the patient is at the time of RT. There is also an increased risk of osteoporosis (especially involving the spine) and degenerative disease. The degree of damage depends on the total dose, fractionation, and field of radiation. Treating only part of the vertebral column, as used in flank irradiation before 1960, resulted in differential growth of the spine and subsequent development of spinal deformities, but using an altered technique in which the entire vertebral body is irradiated prevented some of the severe deformities. However, per Wright et al, studies continued to report occurrence rates of kyphosis and scoliosis between 10% and 70%, the wide range reflecting the difference between clinical and radiological evaluation. Here, we compare 3-D conformal RT to volumetric modulated arc therapy (VMAT) in a primary Wilm’s tumor case to assess vertebral body sparing.Materials/Methods:Vertebral body sparing radiotherapy was planned on a left sided, favorable histology Stage III Wilm’s tumor case. The CTV & PTV were delineated according to AREN0532 guidelines. The tumor bed was contoured as a CTV and PTV of 1cm was generated around the CTV, also accounting for organ motion. The vertebral bodies & intervertebral discs were contoured. 10.8 Gy in 6 fractions were prescribed to 95% of PTV, while reducing the dose to the remaining kidney as low as possible.Plans were generated using standard 3D-CRT & VMAT and were analyzed to assess vertebral body sparing.Results:VMAT plan was dosimetrically superior to 3D-CRT plan. The volume of PTV receiving 10.8 Gy was 88% and 95% for 3D-CRT and VMAT, respectively. The volume of the right kidney receiving greater than 5 Gy was 14.3% versus 4.4% for 3D-CRT and VMAT, respectively. For the vertebral bodies, the volume receiving greater than 3 Gy was 3.4% versus 96% for VMAT & 3D-CRT respectively.Conclusions:Use of VMAT for Wilm’s tumor can provide significant dosimetric advantages over 3D-CRT in delivering the desired dose to the PTV while minimizing the dose to the vertebral bodies in an attempt to avoid any musculoskeletal or growth abnormalities in the future.

Saeed, H, Firat, S, Prah, D, Vertebral Body Sparing in Wilm'S Tumor: Comparison between 3d-crt Vs Vmat.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14043836.html