The evaluation of lung doses for radiation pneumonia risk in stereotactic body radiotherapy: A comparison of intensity modulated radiotherapy, intensity modulated arc therapy, cyberknife and helical tomotherapy

Background: Radiation Pneumonia (RP) is one of the most extensive side effects in Stereotactic Body Radiotherapy (SBRT) of lung cancer. SBRT are performed by means of Intensity Modulated Radiotherapy (IMRT), Intensity Modulated Arc Therapy (IMAT), CyberKnife (CK) or Helical Tomotherapy (HT) treatment methods. In this study, we performed a plan study to determine the plan parameter such as the Mean Lung Dose (MLD), V20Gy Lung Volume and V5Gy Lung Volume in the evaluation of RP risk in the treatment of lung with SBRT. Materials and Methods: Fifteen patients with Lung Cancer who had a tumor diameter of less than 5 cm and peripheral located were included to this study. Intensity Modulated Radiotherapy, Intensity Modulated Arc Therapy, CyberKnife and Helical Tomotherapy plans were separately created for each patients. For each plan, a total of 54 Gy dose were given to Planning Target Volume (PTV) in 3 fractions using a dose of 18 Gy per fraction. Results: In each technique for all parameters of PTV and critical organ doses (OAR) meet the required criteria. Total Lung MLD were found as 3.21 Gy and Total Lung V20Gy Volume were found as 4.05 cc,  Total Lung V5Gy Volume were found as 14.06 cc as the lowest value in IMRT-SBRT plan. Conclusion: When treatment plans are evaluated in terms of RP risk, Total Lung MLD,  Total Lung V20Gy Volume and Contralateral Lung V5Gy Volume are found the lower in IMRT- SBRT plan than other SBRT techniques. We suggest that IMRT-SBRT irradiation should be preferred in lung radiotherapy in case of high RP risk.