Dosimetric comparison of 3 dimensional conformal radiotherapy wi̇th intensity modulated radiotherapy and volumetric modulated arc therapy in soft tissue sarcoma: A planning comparison study

In this study, instead of making radiotherapy plans with three dimensional conformal radiotherapy (3DCRT) as in clinical routine for soft tissue sarcoma, we made radiotherapy (RT) plans with intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT), which delivers more homogeneous planning target volum (PTV) dose and gives less dose to organs at risk (OAR). Patient with soft tissue sarcoma receive only radiotherapy treatment as well as combination with surgery or chemotherapy. In radiotherapy, patient occurs secondary disorders or have less quality performance in their life due to high doses. Neoadjuvant radiotherapy is preferred in order to prepare the ground for extremity-preserving surgical treatment in soft tissue sarcomas, which are usually located in extremities. Recent development in radiotherapy also effect RT plannig modalities. Because of rapid, easy and user friendly software, IMRT and VMAT come forward with homogeneous, conformity dose distribution on PTV and less dose at OAR against 3DCRT. In this thesis, treatment plans was created by technique of IMRT, VMAT and 3DCRT for 10 patients who diagnose with soft tissue sarcoma. In 3DCRT techniques, 6 megavolt (MV) photon energy was used to AP-PA fields. The plans of IMRT technique that consist 7 non-opposing fields with 6 MV photon energies and VMAT technique that consist 2 partial arc with 6 MV photon energies. IMRT fields or VMAT arcs are modified to spare contralateral legs. For every modalities, prescription dose is the same; 2grays/fraction in 25 fractions, total 50 grays. After normalized these three technique that 95% of PTV volume to receive 100% of the prescriped dose, for CTV95 doses 3DCRT-IMRT (p=0.285), 3DCRT-VMAT (p=0.333), IMRT-VMAT (p=0.919), significance level of techniques reflect no advantages between them. CTVmean doses, 3BKRT-YART (p=0.575), 3BKRT-VMAT (p=0.285), YART-VMAT (p=0.213), are also shows no advantages between any techniques. For PTV homogeneity index values, 3DCRT-IMRT (p=0.093), 3DCRT-VMAT (p=0.028), IMRT-VMAT (p=0.333), VMAT technique has advantage over 3DCRT technique but no level of significant between other techniques. And for dose conformity, 3DCRT-IMRT (p=0.005), 3DCRT-VMAT (p=0.005), IMRT-VMAT (p=0.005), VMAT has more andvantage than other two technique and IMRT become superior to 3DCRT technique. Assessment of critical structure, for bone, Dmean values showed that 3DCRT-IMRT (p=0.646), 3DCRT-VMAT (p=0.169), IMRT-VMAT (p=0.114), there is no level of significant between any technique. For V40 values, 3DCRT-IMRT (p=0.037), 3DCRT-VMAT (p=0.009), IMRT-VMAT (p=0.007), VMAT technique has more advantage than other two techniques and IMRT technique has become superior to 3DCRT technique. For V50 values, 3DCRT-IMRT (p=0.005), 3DCRT-VMAT (p=0.005), IMRT-VMAT (p=0.005), also showed same result as V40 values. And other critical structure, skin, Dmean values showed that 3DCRT-IMRT (p=0.028), 3DCRT-VMAT (p=0.386), IMRT-VMAT (p=0.005), VMAT become superior to IMRT and IMRT become superior to 3DCRT for statistically. For V20 values, 3DCRT-IMRT (p=0.007), 3DCRT-VMAT (p=0.093), IMRT-VMAT (p=0.005), VMAT has more advantage than IMRT and IMRT has more advantage than 3DCRT technique. For V30 values, 3DCRT-IMRT (p=0.646), 3DCRT-VMAT (p=0.093), IMRT-VMAT (p=0.013), VMAT has become statistically more advantage than IMRT technique. As a result, comparison of three techniques reflect, IMRT and VMAT technique have more advantages than 3DCRT, both target volumes and critical structures. Key Words: Soft Tissue Sarcoma; 3DCRT; IMRT; VMAT