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http://online.myiwf.com/astro2014/Abstract.aspx

Significantly Improved Normal Tissue Dose Delivery Of Brachytherapy Over Sbrt For <5cm Lung Cancer: A Dosimetric Study Of A Novel Lung Brachytherapy Technique.

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Session Title: Digital Poster Discussion 07 : Physics - Innovative Planning and Delivery Strategies
Date: 9/16/2014
Time: 1:00 p.m. - 2:30 p.m.
Presentation Number: 1073
Room Number: Hall D, Room D-1
Track: Physics


Author(s)
B. Parashar1, A. Pham2, S. Trichter2, A. Wernicke2, D. Nori2, K. Chao2, 1Stich Radiation Center, new york, NY, 2WCMC, new york, NY

Abstract
Purpose: We have initiated a transbronchial lung Brachytherapy (using navigational technology) program using Cesium-131 for patients with recurrent lung cancer after primary radiation or patients with lesions close to the central tracheobronchial tree that are a challenge to treat with stereotactic body radiation therapy (SBRT). The aim of the current study is to evaluate normal tissue radiation dose evaluation with Cs-131 Brachytherapy, and comparison with SBRT for lesions < 5 cm.
Methods: Eighteen consecutive patients with early stage lung cancer, treated with definitive SBRT in our department (2011-2013) were included in our study. All patients had biopsy proven malignancy and had received SBRT to a total dose of 4800cGy in 1200cGy fractions (4 fractions). Radiation plans including Dose volume histograms (DVHs) were evaluated for each patient. CT images obtained at the time of SBRT planning were transferred to our Brachytherapy planning system (Brachyvision, Varian Inc). This planning software was used to ‘virtually’ implant each of these patient’s lung nodules with Cs-131 (activity;2.4U) to achieve a dose of 10000cGy (100Gy) to the target. This dose was selected based on our post-op lung brachytherapy data where 60-80Gy has been used as the appropriate prescription dose. All relevant normal tissue targets were contoured and maximum dose to each organ calculated. Wilcoxon signed rank test was used to analyze the difference between SBRT versus Cs-131 Brachytherapy.
Results: There were 13 females and 5 males. The median age was 75 years (Range 58-92). Median tumor size was 1.6 cm (range 1.1-4.3cm). The number of seeds needed to achieve the prescription dose ranged from 18 to 120. The maximum dose to each normal structure from both SBRT and Brachytherapy plans was calculated as a percentage of the prescribed dose. Percent radiation dose (percentage of prescription doses) to the spinal cord, esophagus, trachea and bronchial tree, and major blood vessels was significantly lower in the Brachytherapy group compared to the SBRT group. Median percent dose to the spinal cord was 2.61 % and 20.09 % respectively (P=0.002), while median percent dose to the esophagus was 4.17 % and 36.27 % (P=0.004) for Brachytherapy and SBRT respectively. Median percent dose to the trachea and bronchial tree was 6.9 % and 40.02 % (P=0.016), while median percent dose to the major blood vessels was 9.43 % and 51.55 % (P=0.014) for brachytherapy and SBRT respectively. There was no significant difference in median percent dose to the ribs, heart or non-tumor lung fields.
Conclusion: Our dosimetric results suggest a significant improvement in normal tissue dose distribution with the use of Brachytherapy compared to SBRT. As a part of our initiative using transbronchial lung brachytherapy for <5cm lung nodules, this novel technique may be quite useful to deliver safe and effective doses for challenging lung cancer nodules.


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