Dosimetric analysis of intensity modulated radiotherapy (IMRT) and three dimensional conformal radiotherapy (3DCRT) for treatment of non-small cell lung cancer: A comparative study

Purpose: The purpose of this study is to analyze and compare the dosimetric parameters of three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) in selected non-small cell lung cancer (NSCLC) cases. Methods: Ten patients with inoperable NSCLC were selected for this study. The 3DCRT and IMRT plans were generated for all patients following Radiation Therapy Oncology Group (RTOG) guidelines. Generated plans were then compared on the basis of planning target volume (PTV) coverage, dose delivered to organs at risk, homogeneity index (HI), and conformity index (CI) for the prescribed dose (PD) of 50 Gy in 25 fractions. Results: The mean D95 and D99 (dose to the 95% and 99% volume) for the PTV were found better in the 3DCRT plans compared to the ones in the IMRT plans. On an average, the volume receiving 20 Gy (V20) of contralateral lung was 2.91% and 3.03% in the 3DCRT and IMRT plans, respectively. The Dmean of contralateral lung was 3.17 Gy (3DCRT) versus 4.2 Gy (IMRT), whereas the Dmean of ipsilateral lung was 12.69 Gy (3DCRT) and 13.82 Gy (IMRT). The V20 of ipsilateral lung was found to be slightly lower in the 3DCRT (25.67%) when compared to the IMRT (30.50%). The dose to the heart was comparable in the 3DCRT and IMRT plans (mean dose: 4.42 Gy versus 4.48 Gy; D33: 3.77 Gy versus and 4.02 Gy). For the spinal cord, the Dmax was found to be lower in the 3DCRT plans (18.40 Gy) when compared to the IMRT plans (25.49 Gy). The HI was 1.08 versus 1.41 in the 3DCRT and IMRT plans, respectively. The CI was identical (1.67) in both sets of plans. Conclusion: Based on the results of this study, the PTV coverage was found to be slightly better in the 3DCRT plans when compared to the one in the IMRT plans. On average, the dose to the organs at risk were found to be comparable.