Abstract
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 D 95 and D 99 (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 (V 20 ) of contralateral lung was 2.91% and 3.03% in the 3DCRT and IMRT plans, respectively. The D mean of contralateral lung was 3.17 Gy (3DCRT) versus 4.2 Gy (IMRT), whereas the D mean of ipsilateral lung was 12.69 Gy (3DCRT) and 13.82 Gy (IMRT). The V 20 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; D 33 : 3.77 Gy versus and 4.02 Gy). For the spinal cord, the D max 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.
Highlights
Radiotherapy is an integral part of non-small cell lung cancer (NSCLC) management and using this therapy the main aim is to treat patient with less complications
This study aims to evaluate the 3DCRT and intensity modulated radiotherapy (IMRT) planning techniques for the selected NSCLC patients
The mean dose to 95% (D95) and 99% (D99) of planning target volume (PTV) was 96.50% (Standard deviation (SD): 1.48) and 94.45% (SD: 2.02) for 3DCRT and 94.76% (SD: 2.07) and 90.49% (SD: 4.02) for IMRT, respectively
Summary
Radiotherapy is an integral part of non-small cell lung cancer (NSCLC) management and using this therapy the main aim is to treat patient with less complications. In the early 1990s, three dimensional conformal radiation therapy (3DCRT) using CT images was standard method to deliver radiation using a set of intersecting beams of two dimensional shapes, from which three dimensional high dose region of approximately tumor shape can be achieved to treat the cancer. In IMRT, the intensity of each beam is modified with the help of multi leaf collimators (MLC) according to the shape of the tumor. With this technique any tumor shaped can be acquired having sudden dose fall outside the region of interest. The use of IMRT technique increased over the last decade but there are certain limitations of this technique, IMRT plans are complex and inappropriate where intrafractional motion of the target is large, such as in lung tumors.[1]
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