Application Of AUTO-plan In Radiotherapy Planning For Breast Cancer After Breast Conserving Surgery

Objective:To explore the feasibility of AUTO-plan in the radiotherapy of breast cancer patients by comparing the reverse optimized artificial plan（ARP）and AUTO-plan（AUTO-plan）for breast cancer patients.And provide evidence for its clinical application.The dosimetric parameters of AUTO-plan in radiotherapy for breast cancer patients were analyzed to provide data support for the application of AUTO-plan in radiotherapy for other types of cancer patients,so as to relieve the work pressure of clinical physicists.Methods:Randomly selected 50 breast cancer patients taking breast conserving surgery in our department were from January 2017 to May 2018.Their clinical stage was T1-2N0-1M0 and the prescription of preventive irradiation was planning Target Volume（PTV）25 times/2 Gray（Gy）,the total dose was 50 Gy.Fixed breast brackets were used.The patients were supine,with both hands on their heads and put foam pillow under mandible to fix head.Siemens 800 mm wide-aperture 24-slice spiral CT scan with a slice thickness of 5 mm was uploaded to Philips Pinnacle version 9.10 Treatment Plan System（TPS）.According to the NNCN guidelines of the 2017 edition and RTOG 9804report requirements,the TPS outlined the PTV,affected lung tissue,contralateral lung tissue,heart,humerus head,contralateral breast and other vulnerable organs（The Organs at Risk,OAR）.Using Philips Pinnacle version 9.10 TPS system,50 patients were designed artificial plan and AUTO-plan,the artificial plan was the control group,the AUTO-plan was the experimental group,and the MU,the Coverage Index（CI）and the Uniformity Index（Uniformity Index）of the machine were calculated under the condition that the prescription dose of 100%covered 95%PTV volume.A:Relative Volume of 40 Gary(V₄₀),V30,Mean Dose（Dmean）,b:V₅,V₁₀,V₂₀,Dmean of the affected lung,c:Max Dose（Dmax）of the contralateral breast,etc.SPSS 20 was used for statistical analysis of two different plans.Results:（1）The CI of PTV in AUTO-plan（0.74±0.06）was slightly lower than that in manual planning group（0.77±0.05）（p<0.01）.（2）The HI of PTV in AUTO-plan（1.0529±0.06）was slightly higher than that in manual planning group（1.0545±0.05）（p<0.05）.（3）Evaluation index of crisis organ:A:AUTO-plan optimized plan of heart V₄₀（1.46+0.81）%,V30（2.34±1.10）%,Mean dose（157.76±124.97）cGy,Superior to artificial heart groupV₄₀（1.56±0.86）%、V₃₀（2.55±1.1.17）%、Mean dose（174.39±138.77）cGy,（p<0.01,p<0.01,p<0.01）There was statistical difference between the two groups.B.AUTO-plan optimizes plan of lungV₅（22.81±5.22）%、V10（16.29±4.58）%、V20（10.87±4.14）%and D_max（616.10±180.81）cGy,obviously Superior to artificial lung group V₅（25.05±5.67）%、V10（17.94±4.76）%、V₂₀（11.81±3.96）%、D_max（653.0±184.3）cGy,（p<0.01）,There was statistical difference between the two groups.C.Though AUTO-plan optimizes plan of breast D_max（288.88±279.10）cGy,obviously Superior to artificial breast group D_max（310.41±290.25）cGy,（p>0.05）,There was no difference between the two groups.（4）Machine parameter evaluation index:The MU number of manual planning group and Auto-plan group were（102.76±14.1）and（109.98±26.33）respectively,p>0.05,and the difference of MU number between the two groups was about 7 hops,which had no statistical significance;the design time of manual planning group was 71.4±18.05min,more than that of Auto-plan group[（84.76±17.46）min,（13.36±3.21min）;（p<0.01）],There was statistical significance between the two groups.Conclusion:（1）Although there are differences in CI,HI between AUTO-plan optimization program and artificial plan for PTV,AUTO-plan optimization program can completely meet the clinical treatment requirements;（2）Intelligent treatment based on Auto-plan optimization conditions,AUTO-plan optimization program endangered organs limit is significantly better than manual plan;and the optimization time is significantly less than manual plan;（3）the AUTO-plan optimization plan can be applied in clinic from the perspective of clinical metrology.