Dosimetric Comparison of Three-Dimensional Conformal Radiotherapy with Hybrid Intensity-Modulated Radiotherapy Techniques for Treatment of Locally Advanced Lung Cancer

OBJECTIVE Radiation treatment planning for advanced lung cancer can be technically challenging, as the delivery of doses of >= 60 Gy is often associated with significant risk of normal tissue toxicities. We aimed to examine the effect of the hybrid technique combining three-dimensional compared radiotherapy (3DCRT) with intensity-modulated radiotherapy (IMRT) on target dose distribution and critical organ doses. METHODS The treatment plans of nine patients treated with 3DCRT were replanned using hybrid technique. 3DCRT consisted of 3-5 fields using 6-18 MV energies and IMRT plans consisted of 7-10 fields using 6 MV energy. In hybrid plans, 60% of the prescribed dose were delivered with 3DCRT and 40% with IMRT beams. Prescribed dose was 66 Gy in 2 Gy fractions. RESULTS Hybrid IMRT improved dose homogeneity in planning target volume (PTV). It was possible to reduce the hotspots that exceeded 107% of the prescribed dose with the hybrid technique compared to 3DCRT (p=0.028). Total and contralateral lung doses were found to be increased with hybrid technique. Hybrid IMRT decreased maximum esophagus and spinal cord doses. CONCLUSION Hybrid IMRT improved dose homogeneity in PTV and decreased hot spots but increased lung doses. The lower maximum point doses of esophagus and spinal cord were achieved with hybrid technique. Reducing the number of fields and contribution of IMRT fields might increase the advantage of hybrid technique by reducing lung doses.