Dosimetric comparison of two different planning technique applied in lung cancer radiotherapy

Objective: The aim of this study is to compare two radiotherapy techniques in non-small cell lung cancer (NSCLC) patients in terms of target volume and critical organ doses. Method: The treatment plans of 9 patients who were diagnosed with locally, advanced NSCLC and treated with three-dimensional conformal radiotherapy were replanned with Hybrid technique. The hybrid plans were made in a way that 60% of the total fractionwould be applied with three-dimensional conformal radiotherapy and 40% with Intensity modulated radiotherapy and 66 Gy was applied in total. Spinal cord, heart, lung and oesophagus were contoured as critical organs. The target volume, critical organ volumes, homogeneity index (HI) and conformity index(CI) were compared. T-test and Wilcoxon tests were used for statistical analysis and p < 0,05 was considered significant. Results::Even though there were no statistical differences found between the two techniques considering 95% isodose encompassing the target volume, it was possible to provide a more homogenous dose distribution with Hybrid technique. In addition, it was possible to keep the hot spots exceeding %107 lower with Hybrid technique. But the V5 value that the opposite lung received was found significantly higher with Hybrid technique statistically(p < 0,05). While no difference was found between the two techniques in terms of the doses received by heart, oesophagus and the maximum dose received by spinal cord wasfound to be lower with Hibrit technique. Conclusion: With the Hybrid techniquehaving 60% of 3DCRT and 40% of IMRT, it's possible to provide more homogenous dose distribution and to keep the hot spots above %107 lower and achieve a more homogenous dose distribution. In addition,the dose that normal tissues such as oesophagus and spinal cord take may be lowered, but it may cause an increase in the volumes receiving low or median dose. Key words: Radiotherapy, NSCLC, 3DCRT, Hybrid technique.