Avoiding Dosimetric Risk Factors for Complications in Neoadjuvant Chemoradiotherapy for Lung Cancer: Conventional Radiotherapy Intensity-modulated Radiotherapy.

Background/aim: We compared three-dimensional conformal radiotherapy (3D-CRT) with intensity-modulated radiotherapy (IMRT) for avoiding dosimetric risk factors related to pulmonary complications after neoadjuvant chemoradiotherapy followed by surgery (NACRT-S) for non-small cell lung cancer (NSCLC).

Patients And Methods: We performed simulations in 11 patients with dosimetric risk factors during their treatment with NACRT-S for NSCLC. Radiation treatment plans were generated using 3D-CRT and IMRT to avoid dosimetric risk factors. Regarding dose-volume histogram (DVH) parameters, we calculated the percentage of lung volume that received more than x Gy (V) using 1) the total lung volume minus gross tumor volume (DVH), 2) the lung volume remaining after surgery (DVH), and 3) the contralateral lung volume (DVH). We analyzed the dosimetric differences between 3D-CRT and IMRT.

Results: V and V were significantly lower with IMRT than with 3D-CRT (p=0.001 each); the median V and V were 16.1% and 14.9% with 3D-CRT versus 12.0% and 9.2% with IMRT, respectively. Overall, 0% and 55% of the patients were able to avoid all dosimetric risk factors with 3D-CRT and IMRT, respectively (p=0.006). Even with IMRT, tumor location and length of the planning target volume (PTV) significantly affected the avoidance of all dosimetric risk factors (p=0.015 and 0.022, respectively).

Conclusion: IMRT is more useful than 3D-CRT for avoiding dosimetric risk factors in NACRT-S for NSCLC. For further improvements in avoiding these factors, respiratory motion managements to reduce the length of the PTV may be required for patients with middle or lower lobe tumors.