Effect of lung volume on helical radiotherapy in esophageal cancer: are there predictive factors to achieve acceptable l
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ORIGINAL ARTICLE
Effect of lung volume on helical radiotherapy in esophageal cancer: are there predictive factors to achieve acceptable lung doses? Meltem Kirli Bolukbas1,2
· Sibel Karaca1
Received: 7 October 2019 / Accepted: 7 January 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Purpose The dose received by the lungs in radiotherapy (RT) is affected by the patient’s current lung volume. The presence of predictive factors and cut-off points were investigated to achieve acceptable lung doses in esophageal cancer (EC) treatment. Methods Virtual RT volumes of supracarinal EC were delineated. RT plans were designed with standard criteria in the TomoTherapy planning system (TomoTherapy Inc., Madison, WI, USA). The total dose was 50.4 Gy (1.8 Gy/fraction). ROC (Receiver operating characteristic) analysis and Mann–Whitney U tests were performed. Results There was a total of 65 patient plans included. ROC analysis showed that lung/PTV (Planning target volume) volume ratio (AUC [Area under curve]: 0.91, 95% CI: 0.83–0.99, p = 0.000) and bilateral lung volume (AUC: 0.81, 95% CI: 0.70–0.92, p = 0.000) have diagnostic power to predict the suitability of RT plans according to QUANTEC (Quantitative Analyses of Normal Tissue Effects in the Clinic) for lung dose constraints. The cut-off points of 7 and 3500 cc were selected for lung/PTV ratio and bilateral lung volume, respectively. The effect of the cut-off points on the dose data was assessed with the Mann–Whitney U test. The mean lung and heart doses, lung V5, V15, and V20, as well as heart V5, V20, V30, and V45 values were found to be lower in both groups separated by cut-off points (p < 0.05). Conclusion The lung/PTV ratio ≥7 and bilateral lung volume ≥3500 cc cut-off points are predictive of whether TomoTherapy plans may meet QUANTEC lung dose limits in patients with supracarinal esophageal cancer. The patients with lung/PTV ratio and lung volume above these cut-off points may be candidates for treatment with TomoTherapy.
Keywords Esophageal cancer neoplasms · Normal tissue sparing · Dosimetric effects · Helical TomoTherapy · Dose-volume parameters
Introduction Esophageal cancer (EC) is a rare type of cancer and it has critical importance among the cancer types due to the high mortality rates. According to the SEER (Surveillance, Epidemiology, and End Results) database, EC accounts for 1% of all malignancies and the 5-year survival rate is 19.2% [1]. Half of the newly diagnosed EC patients are not eligible for Meltem Kirli Bolukbas, M.D.
[email protected] Sibel Karaca, Ph.D. [email protected] 1
Department of Radiation Oncology, Health Sciences University Erzurum Regional Training and Research Hospital, Caykara street, 25100 Erzurum, Turkey
2
Department of Radiation Oncology, Kocaeli State Hospital, Izmit, Kocaeli, Turkey
surgery because they are in the locoregional or metastatic stage [2]. Radical chemoradiotherapy was accepted as the standard treatment for patients who are not suitable for surgery by the RTOG (Radiation Thera
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