Comparison of Hybrid Techniques with 3D-Conformal Radiotherapy in Patients with Lung Cancer

Abstract

Purpose: It’s postulated that hybrid techniques (HT) with lower weighting of IMRT/VMAT component would improve lung dose-volume parameters despite some disadvantage in PTV homogeneity index (HI) and target coverage (TC). Material and Methods: Conformal plans were prepared using 6-10-15 MV-X photon energies while IMRT/VMAT plans of HTs were prepared using 6MV-X. Four HTs were developed having two different ratios (10% and 50%) of IMRT/VMAT component (h-IMRT1, h-IMRT2 and h-VMAT1, h-VMAT2, respectively). HTs were compared with 3D-CRT in terms of HI and TC for PTV, and total lung (TL) and contralateral lung (CL) V5Gy, V10Gy, V20Gy and mean lung dose (MLD). Results: All HTs were advantageous for HI and TC, while disadvantageous for TL and CL-V5Gy. H-IMRT2 provided better TC than h-IMRT1, and so did h-VMAT2 compared to h-VMAT1. Lower weighting of IMRT/VMAT decreased TL and CL-V5Gy in HTs. In addition, h-IMRT1 decreased TL and CL-MLD and CL-V20Gy compared to h-IMRT2, while h-VMAT2 decreased TL-V20Gy and CL-MLD compared to h-VMAT2. Conclusion: In the RT of lung tumors close to vertebra, it may be appropriate to suggest a ratio of IMRT/VMAT component about 10% in order to decrease the low and intermediate dose-wash lung volume, if HI and TC values are acceptable.

Keywords

• lung cancer
• radiotherapy
• treatment planning
• hybrid technique
• volumetric modulated arc therapy
• intensity modulated radiation therapy

References

1. Mayo C, Urie M, Fitzgerald T, Ding L, Lo YC, Bogdanov M. Hybrid IMRT for treatment of cancers of the lung and esophagus. Int J Radiat Oncol Biol Phys, 2008; 71: 1408-1418.
2. Agapito J. On the possible benefits of a hybrid VMAT technique in the treatment of non–small cell lung cancer. Med Dosimetry, 2013; 38: 460-466.
3. Rosca F, Kirk M, Soto D, Sall W, McIntyre J. Reducing the low-dose lung radiation for central lung tumors by restricting the IMRT beams and arc arrangement. Med Dosimetry, 2012; 37: 280-286.
4. Jiang X, Li T, Liu Y, et al. Planning analysis for locally advanced lung cancer: dosimetric and efficiency comparisons between intensity-modulated radiotherapy IMRT, single-arc/partial-arc volumetric modulated arc therapy SA/PA-VMAT. Radiat Oncol, 2011; 6: 140-7.
5. Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys 2008; 35:310-7.
6. Murshed H, Liu H, Liao Z, et al. Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non-small-cell lung cancer. Int J Radiat Oncol Biol Phys, 2004; 58: 1258-67.
7. Bree I, Hinsberg M, Veelen L. High-dose radiotherapy in inoperable nonsmall cell lung cancer: Comparison of volumetric modulated arc therapy, dynamic IMRT and 3D conformal radiotherapy. Med Dosimetry, 2012; 37: 353-357.
8. Court L, Wagar M, Berbeco R, et al. Evaluation of the interplay effect when using rapidarc to treat targets moving in the craniocaudal or right-left direction. Med Phys, 2010;37: 4-11.

9. Schwarz M, Van der Geer J, Van Herk M, Lebesque JV, Mijnheer BJ, Damen EM. Impact of geometrical uncertainties on 3D CRT and IMRT dose distributions for lung cancer treatment. Int J Radiat Oncol Biol Phys, 2006; 65 (4): 1260-9.
10. Chan OS, Lee MC, Hung AW, Chang AT, Yeung RM, Lee AW. The superiority of hybrid-volumetric arc therapy (VMAT) technique over double arcs VMAT and 3D-conformal technique in the treatment of locally advanced non-small cell lung cancer. Radiother Oncol, 2011; 101: 298-302.
11. Verbakel W, Reij E, Ladenius-Lischer I, Cuijpers J, Slotman BJ, Senan S. Clinical application of a novel hybrid intensity-modulated radiotherapy technique for stage III lung cancer and dosimetric comparison with four other techniques. Int J Radiat Oncol Biol Phys, 2012; 83: 297-303.