Comparison Of The Methods Of Simultaneous Integrated Boost And Sequential Electronic Boost Radiotherapy After Breast-conserving Surgery In Early Breast Cancer

Objective: To investigate the target doses of two types of radiotherapy methods for early breast cancer breast-conserving surgery after simultaneous integrated boost intensity modulated radiotherapy?SIB-IMRT?and sequential electronic boost radiotherapy for whole breast IMRT.Differences in target volume,dose,and dose to organs at risk,and observation of the differences in early radiotherapy complications and skin cosmetic effects of the two tumor bed supplemental irradiation methods,and selecting for patients more optimized treatment options.Methods: From January 2017 to February 2019,150 patients were selected from the Affiliated Hospital of Southwest Medical University who were pathologically diagnosed as early breast cancer(T_1²N_0¹M₀,?^?)and completed breast conserving surgery and radiotherapy in the oncology department,with a median age of 47 years.Among them,80 patients with lesions on the left side and 70 patients on the right side.The patients were treated with simultaneous integrated boost IMRT and sequential electron line boost after whole breast IMRT.Two methods were used for postoperative adjuvant radiotherapy,SIB-IMRT group contains 97 patients,sequential boost radiotherapy group contains 53 patients.Refer to the Chinese Anti-Cancer Association Breast Cancer Diagnosis and Treatment Guidelines and Specifications?2017 edition?to outline the whole breast and tumor bed target area on the Oncentra system or Pinnacle9.10 system.Use Pinnacle9.10 radiotherapy planning system to design the radiotherapy plan.The simultaneous boost group's patients were treated with simultaneous integrated boost IMRT?SIB-IMRT?,6MV X-rays,and the prescribed dose was whole breast PTV: 50 Gy / 25 F,the dose was divided into 2Gy / F,and the tumor bed PTV-tb: 60 Gy / 25 F,the dose was divided into 2.4Gy / F,a total of 25 times;sequential electronic boost group's patients were treated with sequential electron beam boost radiotherapy after whole breast IMRT,and 6MV X-rays were used for whole breast irradiation.The prescribed dose was Whole breast PTV: 50 Gy / 25 F,the dose was divided into 2Gy / F,a total of 25 times.After the completion of whole breast radiotherapy,the electronic wire boost was performed at a later stage.?-rays of 9-15 Me V are used,and the prescribed dose was 10-16 Gy.The dose was divided into 2Gy / F,average 5-8 times.Organs at risk?OAR?included bilateral lung,heart,undisturbed breast,spinal cord,liver,humeral head,throat and esophagus.Compared the differences in target volume,dose,and dose to organs at risk to the two radiotherapy plans,as well as the differences in early radiotherapy toxicities and skin cosmetic effects of the two radiotherapy methods.The results were statistically analyzed using SPSS17.0 software.Results:The average volume of tumor bed PTV of SIB-IMRT group was 98.87cm3,the volume of whole breast CTV was 501.42cm3,the volume of whole breast PTV was 660.78cm3,and the ratio of tumor bed PTV to whole breast PTV average 16.48%;volume of tumor bed PTV of sequential electron line boost group averages 87.89 cm3,volume of whole breast CTV averages 456.48 cm3,volume of whole breast PTV averages 605.81 cm3,ratio of tumor bed PTV to whole breast PTV?VPTV-tumor bed / VPTV-whole breast?averaged 15.66%.There was no significant difference in the above indicators?P> 0.05?.The average tumor bed PTV Dmax of the SIB-IMRT group was 66.14 Gy and Dmean averaged 62.38 Gy.The average tumor bed PTV Dmax of the sequential electron line boost group was 67.74 Gy and Dmean averaged 63.63 Gy.The sequential electron line boost group was larger than the SIB-IMRT group.the difference is statistically significant?P <0.001?;the average CTV Dmax of the whole breast group during the SIB-IMRT group was 66.05 Gy,and the average value of the PTV Dmax was 66.08 Gy;the average CTV Dmax of the sequential electron line boost group was 67.51 Gy,and the average PTV Dmax was 67.70 Gy.The latter is slightly larger than the former,and the difference is statistically significant?P <0.001?.The Dmean of the whole breast PTV under the two radiotherapy methods is 54.98 Gy and 54.89 Gy,respectively.The average doses of PTV D95 were 60.54 Gy and 60.91 Gy,respectively,and the latter dose group was larger,with a significant difference?P = 0.036?.The ratio of the dose of tumor bed PTV D95 to the average dose of tumor bed PTV was 0.9705 and 0.9574,respectively.The SIB-IMRT group was larger than that in the sequential electron line boost group,and the difference was statistically significant?P <0.001?.During the SIB-IMRT group,the maximum heart dose averaged 35.43 Gy,the average dose was 5.12 Gy,V30 averaged 2.20%,and the average lung dose was 9.63 Gy.In the sequential electron line boost group,the maximum heart dose was 39.01 Gy,the average dose was 4.65 Gy,and V30 averaged 2.46%.The average lung dose was 10.03 Gy.There was no significant difference in the above indicators?P> 0.1?.During the SIB-IMRT group,the average lung V20 in the increased dose group was 15.43%,and the sequential electron line boost group was 17.05%.The latter was larger,and the difference was statistically significant?P = 0.016?.The average healthy lung doses were 1.05 Gy and 0.99 Gy,respectively,with no significant difference?P = 0.702?.The maximum dose of the healthy breast in the SIB-IMRT group was 4.19 Gy,with an average dose of 0.72 Gy.The maximum dose of the healthy breast in the sequential electron line boost group was 3.01 Gy,with an average dose of 0.59 Gy.The latter was smaller than the former,and the difference was statistically significant?P <0.05?.During the SIB-IMRT group,there were 73 patients with radiation skin injury in the dose group,of which 61 cases were grade 1?62.89%?,8 cases were grade 2?8.25%?,and 4 cases were grade 3?4.12%?.There were 46 cases in the sequential electron line boost group.There were 37 cases of grade 1?69.81%?;8 cases of grade 2?15.09%?;1 case of grade 3?1.89%?,and the difference was not statistically significant?P=0.116?.There were 16 patients?16.49%?with acute radiation-induced lung injury in the SIB-IMRT group,mainly of grade 1 lung injury;there were 10 cases?18.87%?in the sequential electron line boost group with no significant difference?P=0.715?.Seven patients?7.22%?with advanced radiation-induced lung injury in the SIB-IMRT group had Grade 1 lung injury; 3 patients in the sequential electron line boost group?5.66%?had no significant difference?P=0.716?.In the SIB-IMRT group,43 patients?44.33%?with "excellent" skin cosmetic effect,and 54 patients?55.67%?were "general";13 patients?24.53%?were "excellent",39 patients?73.58%?were "general" and one patient?1.89%?was "poor" in the sequential electron line boost group.The skin cosmetic effect in the SIB-IMRT group was better than the sequential electron line boost group,and the difference was statistically significant?P=0.012?.During the SIB-IMRT group,there were 3 cases of new nodules in the lung and 1 case of local recurrence;1 case of pulmonary nodules,2 cases of recurrence,and 2 cases of persistent leukopenia and thrombocytopenia occurred in the sequential electron line boost group.Conclusion: The volume difference of tumor bed and whole breast target area in the two radiotherapy plan is small;Under the premise that both plans meet the requirements of treatment prescriptions,the target area dose of the SIB-IMRT group is slightly lower than that of the sequential electron line boost group,but the former accounted for a higher proportion of tumor bed D95;the healthy breast and the liver exposure dose in SIB-IMRT group was higher than that in the sequential group,but the V20 of the lung was lower than the latter,and the differences in the doses of the other organs at risk were small,and it was difficult to evaluate the best treatment plan from the dosimetry level;.Under the two radiotherapy methods,there was almost no difference in the incidence of radiation skin injury and radiation lung injury,and the tumor's local control rate of short-term.However,the SIB-IMRT group can shorten the treatment period,so it is more recommended to use SIB-IMRT,but the long-term survival rate needs further follow-up studies to compare.