The Dosimetric Advantages Of The Left Breast Cancer's Chest Wall Irradiation After Modified Radical Mastectomy Between Electron Beam Radiation,X-ray Intensity-modulated Radiation And X-ray And Electron Beam Hybridintensity-modulatedradiation

Objective: To study the dosimetric advantages of the chest wall irradiation between electron beam radiation , X-ray intensity-modulated radiation and X-ray and electron beam hybridintensity-modulatedradiation after modified radical mastectomy of left breast cancer.Methods: 16 patients ofleft breast cancerafter modified radical mastectomywere selected from the Third Affiliated Hospital of Kunming Medical University , between december 2014 to september 2015. 5mm thickness of the equivalent tissue membranewas put on each patient's chest wall.And each patient were fixed with thermoplastic film ,then CT positioning.Finnanlly designing for each patient with three kinds of chest wall radiotherapy treatment planning by using using the three dimensional intensity modulationof Pinnacle9.10treatment planning system: electron irradiation plan (planE) , X-ray intensity-modulated radiation plan (planIMRT) , X-ray and electron beam hybrid modulated radiation plan (planIMRT+E) .three of the planning target volume and organs of dosimetric parameters were assessed and compared.Results:The comparison of target's dosimetric results between the three groups: The comparison of the three groups in PTV Dmax, Dmin, V95, V105, V110, D5, D95, HI,IMRT plan showed best result, E plan had the worst result, the differences of three groupswere statistically significant (P < 0.05) .The comparison of the three groups in PTV Dmean and CI, IMRT+E plan had the best result, the E plan was the worst, the differencebetween the three groups was statistically significant (P < 0.05 ) .The comparison of the three groups in Machine hops, E plan's spill time was the shortest,IMRT+E plan has taken the longest time,the differencebetween the three groups was statistically significant (P < 0.05) .(1) Dosimetric results of lung:The comparison of the three groups in left lung's V5, V10 and right lung's Dmean,E plan was superior to IMRT+E plan and IMRT plan, especially in the left lung's V5 and right lung's Dmean,the differencebetween the three groups was statistically significant (P < 0.05 ) . The comparison of the three groups in left lung's V20, Dmean and whole lung's V20,the E plan had the largest result, and the IMRT had the smallest result, but the difference was not statistically significant (P > 0.05 ) . The comparison of the three groups in whole lung's Dmean, IMRT+E paln had the largest result, and the IMRT had the smallest result,but the difference was not statistically significant (P > 0.05) . (2)Dosimetric results of heart:The comparison of the three groups in heart's V10, Dmean,IMRT+E paln had the largest result, and the E plan had the smallest result, the differencebetween the three groups was statistically significant (P < 0.05 ) .The comparison of the three groups in heart's V30, E plan was superior to IMRT+E plan and IMRT plan, but the difference was not statistically significant (P > 0.05 ) . (3) The comparison of the three groups in right mammary's Dmean, E plan was superior to IMRT+E plan and IMRT plan, the differencebetween the three groups was statistically significant (P < 0.05). There was no significant difference between the three groups in spinal cord's Dmax (P > 0.05).Conclusion:The E plan's target uniformity and conformity is the worst, but the protection of left lung's and heart's low dose volume and right mammary is better than IMRT plan and IMRT+E plan; IMRT plan had the most uniform target dose distribution,increased the low dose volume of heart and lung, existing some deficiency in the protection of OARs; IMRT+E plan's target conformal degree is the best, but the uniformity of dose distribution is a little worse than IMRT paln, existing some cold and hot spots, the IMRT+E plan did not show unique advantage in target dose distribution and OARs'protection .The chest wall radiotherapy of breast cancer postoperative should be modified according to the patients' chest wall contour, chest wall thickness,the thickness of the equivalent radiation category, energy, appropriate filling and radiotherapy technology develop personalized treatment plan.