Dose heterogeneity in the target volume and intensity-modulated radiotherapy to escalate the dose in the treatment of non-small-cell lung cancer
- Department of Radiation Oncology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)
- Section for Medical Physics, University Hospital for Radiooncology, Tuebingen (Germany)
Purpose: To quantify the dose escalation achievable in the treatment of non-small-cell lung cancer (NSCLC) by allowing dose heterogeneity in the target volume or using intensity-modulated radiotherapy (IMRT), or both. Methods and Materials: Computed tomography data and contours of 10 NSCLC patients with limited movements of the tumor and representing a broad spectrum of clinical cases were selected for this study. Four irradiation techniques were compared: two conformal (CRT) and two IMRT techniques, either prescribing a homogeneous dose in the planning target volume (PTV) (CRT{sub hom} and IMRT{sub hom}) or allowing dose heterogeneity (CRT{sub inhom} and IMRT{sub inhom}). The dose heterogeneity was allowed only toward high doses, i.e., the minimum dose in the target for CRT{sub inhom} and IMRT{sub inhom} could not be lower than for the corresponding homogeneous plan. The dose in the PTV was escalated (fraction size of 2.25 Gy) until either an organ at risk reached the maximum allowed dose or the mean PTV dose reached a maximum level set at 101.25 Gy. Results: When small and convex tumors were irradiated, CRT{sub hom} could achieve the maximum dose of 101.25 Gy, whereas for bigger and/or concave PTVs the dose level achievable with CRT{sub hom} was significantly lower, in 1 case even below 60 Gy. The CRT{sub inhom} allowed on average a 6% dose escalation with respect to CRT{sub hom}. The IMRT{sub hom} achieved in all except 1 case a mean PTV dose of at least 75 Gy. The gain in mean PTV dose of IMRT{sub hom} with respect to CRT{sub hom} ranged from 7.7 to 14.8 Gy and the IMRT{sub hom} plans were always more conformal than the corresponding CRT{sub hom} plans. The IMRT{sub inhom} provided an additional advantage over IMRT{sub hom} of at least 5 Gy. For all CRT plans the achievable dose was determined by the lung dose threshold, whereas for more than half of the IMRT plans the esophagus was the dose-limiting organ. The IMRT plans were deliverable with 10-12 segments per beam and did not produce an increase of lung volume irradiated at low doses (<20 Gy). Conclusions: The dose in NSCLC treatments can be escalated by loosening the constraints on maximum dose in the target volume or using IMRT, or both. For large and concave tumors, an average dose escalation of 6% and 17% was possible when dose heterogeneity and IMRT were applied alone. When they were combined, the average dose increase was as high as 35%. Intensity-modulated RT delivered in a static mode can produce homogeneous dose distributions in the target and does not lead to an increase of lung volume receiving (very) low doses, even down to 5 Gy.
- OSTI ID:
- 20698473
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 62, Issue 2; Other Information: DOI: 10.1016/j.ijrobp.2005.02.011; PII: S0360-3016(05)00296-8; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
Similar Records
Multiple fields may offer better esophagus sparing without increased probability of lung toxicity in optimized IMRT of lung tumors
Investigation of Simple IMRT Delivery Techniques for Non-Small Cell Lung Cancer Patients with Respiratory Motion Using 4DCT