Investigating of relationship between the parameters related to the treatment planning and the biological parameters in radiation induced pneumonitis in breast cancer patients

Introduction: The purpose in this study is to analyze of DVH parameters as predictors of radiation pneumonitis and investigation on the relationship between dosimetric and clinical parameters based on PFTs as response in NTCP model and therefore achieve to lung dose- response relation in breast cancer patients. Prescribed dose to treatment volumes was 50 Gy in 2.0 Gy/fractions   Materials and Methods: Clinical and dosimetric data for 51 patients with stages II, III breast cancer who were undergone modified radical mastectomy (MRM) or mastectomy, and they had received prior chemotherapy with a same regimen of 8 steps, were included. Dose delivery technique was SAD and the prescribed dose was 50 Gy in 25 fractions. All of these pulmonary function tests were done before and after completion of radiotherapy, 3 and 6 months afterwards. Relationship between dosimetrical and clinical parameters patients are analyzed according to the univariate logistic regression and by Lyman NTCP model for investigation probability SRP. Results: All of these pulmonary function tests (PFTs) were decreased after completion of radiotherapy, and 6 months afterwards. According to our results, in this research pulmonary complications has appeared from six months after treatment. 17 patients (33.3%) were with radiation pneumonitis without symptoms and 5 (9.8%) patients suffering radiation pneumonitis symptoms with grade 2. Lyman NTCP model parameters were obtained for prediction radiation pneumonitis. Conclusion: Lung dose- response relation was obtained and analyzed according to Lyman NTCP model and DMH as input data in Lyman NTCP model comparison of DVH. IV20, irradiated volume and mass and mean lung dose parameters are related with radiation pneumonitis in patients. Our results indicated that pulmonary function changes occurs at 6 months after RT. we present that in the structure as lung, DMH concept has important effect in the Lyman model