Which Has Better Dosimetry in Retroperitoneal Sarcoma: Rapid Arc or 3D Conformal Radiotherapy Techniques?

Aim: To compare which radiotherapy technique is better in retroperitoneal sarcoma (RPS) rapid Arc (RA) or 3D-Conformal Radiation Therapy (3D-CRT). Methods and materials: Our study was on 10 patients with RPS diagnosed and treated at king Faisal Specialist Hospital & Research Center, Riyadh, Saudi Arabia, planned for pre or postoperative radiation therapy with prescribed dose of 45Gy in 25 fractions. In both techniques, we looked at planning target volume (PTV) coverage, dose homogeneity and organs at risk dose (stomach, bowel, liver, kidneys and spinal cord). Results: The PTV coverage, liver and stomach doses were similar in both plans however; RA significantly had better dose conformity (0.8 vs. 0.4, p = 0.034), dose homogeneity (1.08 vs. 1.3, p = 0.026), less bowel volume (V45 140cc vs. 243cc, p = 0.03) and lower Spinal cord dose (61% vs. 80%, p = 0.043). Conclusion: Both plans achieved similar target coverage and organs at risk sparing however; RA showed statistically significant better dose homogeneity, bowel sparing volume and lower spinal cord dose in treating RPS by pre or postoperative radiation therapy.