Purpose: High-dose-rate (HDR) brachytherapy is attractive modality for several reasons, including steep dose-fall off, less susceptibility to target/organ motion, better sparing of normal tissue and organs at risk (OARs), and reduced chance of geometric miss. Aim of this study is to investigate the potential of HDR brachytherapy as an alternative to stereotactic body radiation therapy (SBRT) for lung cancer treatment.
Methods: Randomly selected 27 patients who had prior SBRT near the chest wall were evaluated by simulating interstitial HDR plans. The HDR plans were created in Oncentra TPS (version 4.5, Ir-192 source), utilizing 5-10 needles inside of the target volume and placed in-between ribs. Clinically used SBRT prescriptions ranged 50-55Gy in 4-5 fractions, while the HDR plans had 30Gy in one fraction.
Results: The HDR plans showed comparable dosimetric coverage of the target volume and marked reduction in the OARs’ doses, especially for the chest wall and ribs. Average values of D1cc, D5cc, and D10cc to the chest wall for SBRT were 50.0Gy, 44.0Gy, and 39.7Gy. Respective HDR doses were 16.5Gy, 11.5Gy, and 9.3Gy. Average maximum dose to the ribs from SBRT was 53.9Gy vs 24.6Gy for HDR. The mean lung dose from SBRT was 6.4Gy, while 1.5Gy was for HDR. For target coverage, average D90 for SBRT was 104.2% of Rx and for HDR was 107.0% of Rx. Average gradient and conformity indices for SBRT were 5.0 and 1.1, and those for HDR were 3.1 and 0.8, respectively.
Conclusion: This study indicates that single fraction HDR brachytherapy can be a plausible and attractive modality for treating selective lung cancer patients who have tumors near the chest wall. The HDR brachytherapy can have similar target coverage, while having considerable reduction in dose to the OARs.