| Non-small cell lung cancer (NSCLC), of which the incidence and mortality is very high, seriously threats human's life. Along with the radiotherapeutic technology's development, the indication of radiotherapy for NSCLC is expanding unceasingly. Now the era of radiation with original and crude equipment is over. The application of advanced accelerator and the simulator equipment, not only greatly improve the prognosis of NSCLC, but also reduce the normal tissue irradiation as much as possible. Three-dimensional conformal radiotherapy (3-DCRT) and intensity modulated radiotherapy (IMRT) declare that the precise radiation'era is coming. The precise radiotherapy presents a series of advanced radiation therapy, which based on the precise positioning, precise plan designing, and precise treatment. In the lung cancer precise radiotherapy, we can reduce position error by the precise positioning equipment, but the breath, which cause the tumor move together, affect the dose escalation of target volume. The contouring of the gross tumor volume(GTV) and the clinical target volume(CTV) is based on the static CT/MRI/DSA/PET image according to ICRU 50# and the 62# reports [2][3], but the target volume shift more or less depend on its location and the organ movement. Formerly, planning target volume (PTV) consisted of the CTV plus a certain margin considering the movement of respiration, which enlarge the radiation field to make sure the target volumes were completely encompassed, but the normal tissue irradiated dose escalated at the same time. If we limited the lung dose to a save level, we can't deliver a high dosage to the target volume. The active breathing control (ABC) technique can get all radiotherapists out of this dilemma.In this study, the 3-D CRT plan were designed respectively via free breath and active breath control condition, and comparative dosimetric study of dose-volume histograms was applied to confirm whether ABC can reduce the irradiated volume of normal tissue and escalate the target volume dosage.From May, 2007 to December, 2007, 15 patients, who were primary diagnosed as NSCLC in the cancer center of China-Japan Union Hospital, were enrolled in this study. Each patient was fixed on the treatment table with the thermal plastics in the supine position with his/her hand across on the head. Then a reference plane was selected and 3 lead marking points were fixed on the thermal plastics in the assist of laser beam. After the confirmation of the positioning, the contrast-enhanced CT scan was completed with free breath and active breath control respectively. The CT scan field including the lung and mediastinum, and every slice is 5mm thick. The image data were sent to the SIM workstation, and the GTV, CTV, normal tissue were outlined according the ICRU 50# and 62# reports via the lung window. The planning target volume (PTV) consisted of the CTV plus 0.5cm margin. The CT scan and target contouring data were sent to the Plato workstation, and the 3-D CRT plans were designed in different breath status respectively. Considering the comparability of the two planning, we make sure the radiation fields and the beam directions were identical in the certain patient's image regardless the breath status. The conventional fractionation regimen was given, 2Gy/f, 60Gy in total. The dose- volume histograms were compared in different breath status, in which there including: the volume, irradiated volume (V), the volume in which the dose exceeded 20Gy (V20) and the mean dose received (Dm) of the involved lung; the volume of GTV, CTV and PTV; the maximal dose of the spinal cord and the mean dose of the heart. The student-newman-keuls statistical method was applied.Results: 1.The V20 of the involved lung is less in ABC group than FB, (17.82±3.94)﹪vs(.26.13±3.88)﹪respectively, P<0.01; the Dm is (1428.76±272.43) cGy,vs.(1695.63±207.50)cGy respectively, P<0.01; in the ABC group the V is much bigger than FB group, (1445.233±280.80) cm3 vs. (1051.20±280.87)cm3 P<0.01. 2. The GTV, CTV and PTV are all smaller in ABC group compared with the FB group, GTV is(24.49±9.14)cm3 vs.(26.12±9.34)cm3,P<0.05; CTV is(48.64±18.39)cm3 vs. (51.65±18.86)cm3,P<0.05; PTV is (88.17±28.92)cm3 vs.(96.21±32.85)cm3, P<0.01. 3. In the ABC group, the spinal cord received a lower dosage than the FB group, is ( 1888.41±567.90 ) cGy vs.(2240.93±62.09)cGy respectively,P<0.05, there is no difference of the heart radiation dose between the two groups.The results indicated that in non-cellule lung cancer 3-D CRT, the use of ABC system can increase the V and the reduce the V20, Dm of the involved lung, at the same time, it can reduce the target volume, and decrease the dose of the spinal cord, which may decrease the incidence of the complication and may improve the local-regional control by escalate the radiation dosage. However it can't reduce the heart spare in our primary test. |
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