Optimizing Collimator Margins for Isotoxically Dose-Escalated Conformal Radiation Therapy of Non-Small Cell Lung Cancer

• Published in: International journal of radiation oncology, biology, physics Vol. 88; no. 5; pp. 1148 - 1153
• Main Authors: Warren, Samantha, PhD, Panettieri, Vanessa, PhD, Panakis, Niki, MD, Bates, Nicholas, MD, Lester, Jason F., MD, Jain, Pooja, MD, Landau, David B., MD, Nahum, Alan E., PhD, Mayles, W. Philip M., PhD, Fenwick, John D., PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2014
• Subjects: Carcinoma, Non-Small-Cell Lung - radiotherapy; COLLIMATORS; Dose-Response Relationship, Radiation; Four-Dimensional Computed Tomography; Hematology, Oncology and Palliative Medicine; Humans; Lung Neoplasms - radiotherapy; LUNGS; Monte Carlo Method; NEOPLASMS; OPTIMIZATION; PATIENTS; Phantoms, Imaging; PLANNING; PNEUMONITIS; Radiation Dosage; RADIATION DOSES; Radiation Pneumonitis - prevention & control; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Conformal - instrumentation; Radiotherapy, Conformal - methods; Retrospective Studies; Risk; SAFETY MARGINS; SCHEDULES; Tomography, X-Ray Computed; Treatment Outcome
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2013.12.034

Purpose Isotoxic dose escalation schedules such as IDEAL-CRT [isotoxic dose escalation and acceleration in lung cancer chemoradiation therapy] (ISRCTN12155469) individualize doses prescribed to lung tumors, generating a fixed modeled risk of radiation pneumonitis. Because the beam penumbra is broadened in lung, the choice of collimator margin is an important element of the optimization of isotoxic conformal radiation therapy for lung cancer. Methods and Materials Twelve patients with stage I-III non-small cell lung cancer (NSCLC) were replanned retrospectively using a range of collimator margins. For each plan, the prescribed dose was calculated according to the IDEAL-CRT isotoxic prescription method, and the absolute dose (D99 ) delivered to 99% of the planning target volume (PTV) was determined. Results Reducing the multileaf collimator margin from the widely used 7 mm to a value of 2 mm produced gains of 2.1 to 15.6 Gy in absolute PTV D99 , with a mean gain ± 1 standard error of the mean of 6.2 ± 1.1 Gy (2-sided P <.001). Conclusions For NSCLC patients treated with conformal radiation therapy and an isotoxic dose prescription, absolute doses in the PTV may be increased by using smaller collimator margins, reductions in relative coverage being offset by increases in prescribed dose.