Optimizing collimator margins for isotoxically dose-escalated conformal radiation therapy of non-small cell lung cancer.

Journal article

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.

Authors: Warren, S; Panettieri, V; Panakis, N; Bates, N; Lester, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Elsevier
• Journal: International journal of radiation oncology, biology, physics
• Volume: 88
• Issue: 5
• Pages: 1148-1153
• Publication date: 2014-04-01
• DOI: 10.1016/j.ijrobp.2013.12.034
• EISSN: 1879-355X
• ISSN: 0360-3016
• Language: English
• Keywords: Retrospective Studies; Monte Carlo Method; Risk; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Conformal; Phantoms, Imaging; Radiation Pneumonitis; Dose-Response Relationship, Radiation; Treatment Outcome; Humans; Lung Neoplasms; Radiation Dosage; Tomography, X-Ray Computed; Carcinoma, Non-Small-Cell Lung; Four-Dimensional Computed Tomography