The comparison of dose distribution of different 3D conformal and conventional radiotherapy plans for gastric cancer

Aims: It was aimed to investigate postoperative conformal radiotherapy planning that provides the best target volume and the least dose for critical organs in cancers of stomach. Methods: This study was conducted on the CT simulation images of thirty patients diagnosed with gastric cancer. Target volumes and the organs at risk were contoured. APPA reciprocal parallel field conventional plan and three and fourfield 3D conformal plans were created using linear accelerator. Target volumes and doses consumed by organs at risk were compared by dosevolume histograms. Results: While a sufficient dose could be applied to target volumes in all plans with conformal planning, average figures showed that 95% of porta hepatis area failed to take the prescribed dose (D95) in some plans by using APPA reciprocal parallel zone conventional plans. The most convenient protection for spinal cord, heart and kidneys was obtained by conformal fourfield technique and the liver doses were increased in conformal fourfield plans but did not exceed the tolerance dose. And also, in the conventional APPA reciprocal parallel field plans, tolerance dose of spinal cord (4500 cGy) was exceeded. Conclusion: In this study, conformal fourfield technique was superior considering target volume dose distributions, and especially spinal cord doses in all localizations and heart doses in cardia tumors. Kidney doses were also reduced in conformal fourfield planning, but failed to reach statistical significance. There was a not exceeding tolerance limits dose increase in liver