Özet:

OBJECTIVE: The aim of this study is to compare two different Conformity Index (CI), Critical organ scoring index (COSI), Tumor control probability (TCP) and Normal Tissue complication probability (NTCP) calculations, and Dose Volüme Histogram (DVH) parameters of 3 different IMRT treatment techniques in prostate cancer patients who underwent pelvic radiotherapy and prostate simultane integre boost (SIB). MATERIAL AND METHODS: In this study, a total of 20 plans with conformal radiotherapy (3DCRT) and different intensity modulated radiotherapy (IMRT) techniques were made in the treatment planning system for 5 prostate cancer patients who had been treated in our clinic. In the evaluation of plans; homogeneity index (HI), mean dose (Dmean), TCP and two different CI values were calculated for all planning target volumes (PTV). Also, DVH data, NTCP and COSI calculations for the rectum, bladder, small intestine and femoral head were found and evaluated. For normal tissue, the volume receiving half of the prescribed dose (V40Gy) and the volume receiving 90% (V72Gy) were evaluated. RESULTS: The RTOGCI mean values for PTV2 and PTV3 were significantly closer to 1 with IMRT plans when compared to 3DCRT plan (P=0.007 and P=0.008, respectively). The PADDICKCI mean values for PTV1 and PTV2 revealed that 3DCRT plans were significantly worse than IMRT plans (P=0.011 and P=0.009, respectively). For the PTV1, according to the CI assessment, the 9IMRT plan was found to be the best, whereas the TCP assessment found the result in favor of the 7IMRT plan. The best plan for bladder and rectum was found 7IMRT. Although the small bowel volume of 195 cc was the best in 3DCRT, the results in the NTCP and COSI evaluation were in favor of 5IMRT. In addition, the lowest volume receiving half of the dose prescribed for normal tissue was found for 7IMRT in both DVH and COSI evaluation. (5.7% and 0.62, respectively). CONCLUSIONS: In the study, the best technique for RTOGCIPTV1 was found to be 3DCRT, which leads to error in the evaluation. This shows that this index is incompatible with reality in multiple PTV definitions. Another index, PADDICKCI, takes into account the PTV and the organs at risk vicinity of the target. However, this index requires an additional equation in the evaluation of SIB plans. Therefore, we consider the use of TCP and NTCP radiobiological evaluation parameters as important tools for selecting the most applicable from multiple plans.

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