Dosimetric Comparison Study Of Intensity-modulated Radiation Methods For Breast-conserving Therapy

Title: Dosimetric comparison study of intensity-modulated radiation methods for breast-conserving therapyObjectives: Breast cancer is one of the most common malignant tumors in women. As the popularity of breast cancer screening, more and more breast cancer was diagnosed at early stage. Radiation therapy plays a vital role on local control in early breast cancer conserving therapy. The improvement of whole-breast radiotherapy technique can reduce the incidence of radiotherapy complications and improve the quality of life. This study compared dosimetric characteristics of three whole-breast radiotherapy plans to prove advantage of IMRT plans for whole breast irradiation after breast conservative surgery and compare dosimetric characteristics of two IMRT plans for clinical optimization.Methods: 15 cases of early-stage left-sided breast cancer after breast-conserving surgery were selected. We used Eclipse system to design three-dimensional conformal, forward field-in-field IMRT and inverse dynamic IMRT plans for whole-left-breast irradiation respectively. Dosimetric parameters were gained in dose volume histograms (DVH) to evaluate dose feature in PTV and OARs,the count of MU was used to compare efficiency difference of two IMRT plans.Results: In planning target volume (PTV) of three-dimensional conformal,forward field-in-field IMRT and inverse dynamic IMRT plans,Dmax were 5583.8±128.4 cGy, 5161.2±77.5 cGy and 5249.5±127.1 cGy respectively (P<0.05), Dmean were 5160.5±94.3 cGy, 5027.4±43.0 cGy and 5002.2±16.8 cGy respectively (P<0.05). V105 were 27.5±18.0 %, 0.6±0.6 % and 0.2±0.2 %(P<0.05),V110 were 6.4±6.8 %,0.0±0.0 % and 0.0±0.0 %(P<0.05), radiation conformal index(CI) were 0.60±0.05, 0.65±0.05 and 0.70±0.04(P<0.05);In organs at risk (OARs) of three plans, Dmax of coronary artery were 5069.2±212.1cGy,4848.9±208.4 cGy and 4446.2±412.2 cGy (P<0.05),V5 in heart were 13.3±9.4 %, 38.7±21.8 % and 41.0±16.4 %(P<0.05),V5 in contralateral breast were 2.7±1.0 %,2.8±1.1 % and 7.3±1.8 %(P<0.05);MU of three plans were 211.6±7.4, 219.8±4.7 and 342.8±23.4 respectively (P<0.05).Conclusion: In the three plans for whole-left-breast irradiation, compared with three-dimensional conformal radiotherapy, dosimetric characteristics of forward field-in-field IMRT and inverse dynamic IMRT plans had improved, but inverse dynamic IMRT plan increased low-dose volume in OARs significantly and may consume more treatment time. So forward field-in-field IMRT plan is recommended.