| Objective:To investigate the relationship between clinical state, dose volume and radiation-induced lung injury in postoperative patients with breast cancer treated by Intensity Modulated Radiotherapy, in order to predict the radiation-induced lung injury and optimize the radiotherapy plan, avoid or reduce the radioactive lung injury, improve the quality of life of patients.Materials and Methods:Between January 2012 and December 2012 in Guangxi Medical University Affiliated Tumor Hospital,A total of 109 female patients with breast cancer who had received postoperative radiotherapy were retrospectively evaluated, which were divided into two groups according to whether radiation-induced lung injury developed. The median age was 45 years (29～73 years); 61 cases of patients undergoing breast conserving surgery and 48 patients underwent modified radical mastectomy surgery;According to the 7th edition of the AJCC staging criteria,among the patients were 31 cases of stage Ⅰ,43 cases of stage Ⅱ and 35 cases of stage Ⅲ; All patients before radiotherapy accepted 3～13 cycles (median for 6 cycles) of systemic chemotherapy, of which 69 cases of 3 to 6 cycles,40 cases more than 6 cycles. Each patient underwent simple IMRT. According to whether the occurrence of radiation-induced lung injury, the relationship between the radiation-induced lung injury and age, surgical approach, the number of cycles of chemotherapy, tumor stage, dosimetric factors were analyzed by univariate and multivariate logistic regression analysis.Results:10 patients were diagnosed as radiation-induced lung injury. The incidence of radiation-induced lung injury was 9.17%(10/109). Univariate analysis showed chemotherapy cycles (χ2=5.825, p< 0.05) were statistically significant factors associated with the development of radiation-induced lung injury. Univariate analysis showed dosimetric factors as the mean dose to ipsilateral lung (t=-4.011, p<0.05),ipsilateral lung V5 (t=-2.771, p< 0.05),ipsilateral lung V10(t=-3.683, p<0.05), ipsilateral lung Vi5(t=-4.113, p< 0.05), ipsilateral lung V2o(t=-4.541, p< 0.05),ipsilateral lung V25(t=-2.747, p< 0.05) were associated with the occurrence of radiation-induced lung injury. Multivariate analysis demonstrated ipsilateral lung V20 was independent predictor (p=0.001).With V20 of 29.03% as the tolerance, the prediction of radioactive lung injury achieved high accuracy (94.5%), with the sensitivity of 80% and the specificity of 96%.Conclusion:Ipsilateral lung V20 was the risk factor for radiation-induced lung injury in patients with breast cancer treated by Intensity Modulated Radiotherapy. Ipsilateral lung V2o=29.03% may be a useful dosimetric parameter to evaluate the risk of radiation-induced lung damage. In the design of breast cancer radiotherapy plan, in addition to set appropriate physical parameters, also need to consider the number of cycles of chemotherapy in patients with, as far as possible to reduce the incidence of radioactive lung injury.Objective:Radiation therapy has the potential to control disease, prolong survival, and improve quality of life for breast Cancer patients. Radiation-induced lung injury is one of the most common complications after breast cancer radiotherapy. Designing of the radiotherapy treatment has a profound effect on the delivery and clinical efficacy of the radiotherapy. So evaluation and optimization the radiotherapy plan in advance to improve the treatment effect and avoid the complication after radiotherapy are particularly important. At present, conventional evaluation of the three dimensional treatment planning system (TPS) making radiotherapy planning mainly adopts physics indicators, and is not fully applied to the radiobiological factors such as the fraction dose size effects and the heterogeneity of tissues or tumor radiation sensitivity. It will be useful to supplement physical methods by evaluation and optimization the radiotherapy plans with radiobiological models such as NTCP. The purpose of the current study was to describe the Lyman NTCP model and explore reasonable model parameters and provide a reference for the selection of clinical radiotherapy plan.Materials and Methods:Between January 2012 and December 2012 in Guangxi Medical University Affiliated Tumor Hospital,A total of 109 female patients with breast cancer who had received postoperative radiotherapy were retrospectively evaluated. All of the patients had no tumor recurrence and distant metastasis, no combined heart and lung diseases. Many people had been ruled out who could not tolerate the radiation and adhere to the completion of radiotherapy, as well as follow-up time <3 months or who lost. Each patient underwent IMRT, their Karnofsky score (karnofsky performance status, KPS) were greater than 70 points and all those people had no history of smoking. The median age was 45 years (29-73 years); 61 cases of patients undergoing breast conserving surgery and 48 patients underwent modified radical mastectomy surgery; According to the 7th edition of the AJCC staging criteria, among the patients were 31 cases of stage I,43 cases of stage II and 35 cases of stage III; All patients before radiotherapy accepted 3-13 cycles (median for 6 cycles) of systemic chemotherapy, of which 69 cases of 3 to 6 cycles,40 cases more than 6 cycles. All patients were in a state of calm breathing with 85cm large diameter spiral CT scans to 5mm thick continuous analog positioning and scanning range from the chin down to the lower edge of the liver. Doctor sketched a target area on CT simulation image, referencing to the latest US radiotherapy Cooperative Group (Radiation Therapy Oncology Group, RTOG) criteria for breast cancer target delineation, Meanwhile defined the spinal cord, heart, lung and contralateral breast for crisis organ (Organ at risk, OAR). A physical application form requires a physician to develop a IMRT plan for each patient according to the physician in charge of the treatment plan. The prescription dose was 50Gy/25 times, the fraction dose was 2Gy,5 times a week, once a day. The require of treatment plan was that 95% of the target dose include 100% of the target volume, the maximum dose point was less than 110% of the prescribed dose, and target volume and the dose of organs at risk within a limited range. Ipsilateral lung:V20<30%, Dmean<20Gy, lungs:V20<20%, heart (left patients only):V30< 10%, V40<5%. Contralateral breast:Dmean <1Gy,Dmax<5Gy.Dose volume histograms with dosimetry data were collected for each patient. A maximum likelihood analysis yielded best estimates for Lyman NTCP parameters. Calculated NTCP value of the 109 patients, and finally statistical software was used to study the new Lyman NTCP prediction effect of the model.Results:10 patients were diagnosed as radiation-induced lung injury. The incidence of radiation-induced lung injury was 9.17%(10/109). The refined NTCP model parameters were m= 0.437, n=0.912, TD5o(1)=17.211Gy。With the modified Lyman NTCP model, the prediction of radiation-induced lung achieved high accuracy of 0.716 (78/109),with a sensitivity of 0.9 (9/10) and a specificity of 0.697(69/99).Conclusion:The modified Lyman NTCP model for radiation-induced lung injury was recommended to predict radiation-induced lung injury in breast Cancer patients treated by Intensity Modulated Radiotherapy. |
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