Post-mastectomy Hypofractionated Radiation Therapy In Breast Cancer Patients– A Phase Ⅰ/Ⅱ Study

Part One Short-term outcomes of post-mastectomy radiation therapy in breast cancer patients with different hypofractionation shemes in breast cancer patientsObjective: To evaluate acute and late toxicities,and short-term outcomes in post-mastectomy patients receiving two hypofractionated radiation therapy shemes.Methods and Materials: Methods and Materials: In this prospective phase I/II study,totally 162 patients were recuited between October 2009 and May 2015.Among these patients,77 were treated with 42.5Gy/16F（2.66Gy/F）sheme,and 85 with36.5Gy/10F（3.65Gy/F）sheme.CBCT guidance was performed before each fraction.Acute and late toxicities were evaluated according to the established RTOG criteria.Survival analyses were practiced.Results: In the 42.5Gy group,the grade 0,1,2,3 and 4 leucopenia was 81.8%,7.8%,7.8%,0% and 2.6%,respectively;the grade 0,1 and 2 acute skin toxicity was31.2%,64.9% and 3.90%,respectively;the grade 0,1and 2 acute pharyngeo-esophageal toxity was 71.4%,27.3% and 1.30%,respectively.In the 36.5Gy group,the grade 0,1,2,3 and 4 leucopenia was 60.0%,28.2%,4.7%,7.1% and 0%,respectively;the grade 0,1and 2 acute skin toxicity was 57.6%,42.4% and 0%,respectively;the grade 0,1 and 2acute pharyngeo-esophageal toxity was 82.3%,16.5% and 1.2%,respectively.No significant difference was detected between the two groups for acute toxicities.During the follow-up period,no late toxicities,such as skin fibrosis,heart toxicity or rib fracture,were observed in the two groups.The median follow-up was 36（26~61）months for the 42.5Gy group.The regional recurrence-free survival（RRFS）was 97.4% and 90.5% at 2 and 3 years,respectively;the disease-free survival was 94.8%,87.9% and 84.3% at 2,3 and 4 years,respectively;the distant metastasis-free survival（DMFS）was 94.25%,74.5% and 59.6% at 2,3 and 5years,respectively.The median follow-up was 12（5~24）months for the 36.5Gy group.The LRFS was 100% at 1 year.The DFS was 96.8% and 93.7% at 1 and 2 years,respectively.The local recurrence-free survival（LRFS）and overall survival（OS）rate were both 100% at 2 and 3 years for both of the two groups.Conclusions: Acute toxicities and short-term outcomes are similar in patients receiving 42.5Gy/16 F and 36.5Gy/10 F of post-mastectomy hypofractionated radiation therapy.Observation for late toxicities and long-term outcomes is undergoing.Part Two Analysis of position errors in breast cancer patients receiving post-mastectomy radiation therapyObjective: To evatuate CTV to PTV expansion via inter-fractional position errors analyses in post-mastectomy patients receiving hypofractioned radiation therapy.Methods and Materials: Fifty-eight post-mastectomy patients were enrolled between September 2013 and December 2015.The median age was 55 years（range,31–63 years）.Twenty-eight patients suffered from right breast cancer,among them 15 cases received chest wall（CW）irradiation and 13 received chest wall and supraclavicular（CW+SC）irradiation.Meanwhile,in patients suffered from left breast cancer,15 received CW irradiation,and 15 received CW+SC irradiation.The prescription dose was 35.6Gy in 10 fractions.CBCT scanning was taken before each fraction.Position errors were recorded in the X（lateral）,Y（longitudinal）and Z（vertical）axes with automatic bone alignment and manual soft tissue alignment.Results: A total number of 580 scannings were taken.Position error in the X,Y and Z axes was（4.5 ± 0.20）mm and（4.5 ± 0.22）mm（p= 0.844）,（4.0 ± 0.19）mm and(4.3 ± 0.21 mm（p= 0.190）,（4.8 ± 0.22）mm and（3.6 ± 0.18）mm（error in the Z axis in patients suffered from left breast cancer was higher than those suffered from right breast cancer,p< 0.001）in left and right breast cancer patients;respectively.Additionally,the position error in the X axis in patients with CW irradiation was higher than those with CW+SC irradiation（left side: 4.1±0.26 mm vs.5.0±0.35,p=0.035,right side: 4.1 ± 0.27 mm vs.5.0 ± 0.35,p=0.048,respectively）.According to the formula equation,MPTV = 2∑+0.7σ,CTV to PTV expansion in the X,Y and Z axes was 6mm,6mm and 5mm;respectively.Conclusions: CBCT guidance can correct inter-fractional position errors in patients receiving post-mastectomy hypofactioned radiation therapy.In our center,these errors were relatively small.The error in the Z axis in patients suffered from left breast cancer was higher than those suffered from right breast cancer,and the error in the X axis in patients with CW irradiation was higher than those with CW+SC irradiation.CTV-PTV expansion in the X,Y and Z axes was 6mm,6mm and 5mm;respectively.More patients are needed to precisely evaluate CTV-PTV expansion.