Comparative Analysis Of The Effect Of Different Radiotherapy Regimes On Lymphocyte And Its Subpopulation In Breast Cancer Patients

Background.Breast cancer is the most common cancer in females around the whole world.Adjuvant radiotherapy plays a significant role in the treatment of breast cancer;it can improve both local control and overall survival,as well as reduce the risk of recurrence and death.With respect to breast cancer irradiation protocols,apart from the standard 50 Gy/25F regime,there are also several hypofractionated schedules with increased dose per fraction and shorter treatment duration.The data of a big clinical trial show no significant difference between conventional and hypofractionated radiation schedules in terms of the risk of local recurrence and overall survival after 10 years of treatment in breast cancer patients prescribed post-surgery radiotherapy.Much has been learnt about the changes of lymphocyte subsets after radiotherapy of one specific fractionated schedule,yet little has been investigated to compare the influence of different RT fraction modelPurpose.The aim of this study was to determine whether different radiotherapy(RT)fractionation schemes induce disparate effects on lymphocyte and its subsets in breast cancer patients.Methods.60 female patients diagnosed with breast cancer were recruited in this study after receiving modified radical mastectomy and were randomly divided into two groups.One group received irradiation at a standard dose of 50 Gy in 25 fractions and the other at a dose of 40.3 Gy in 13 fractions.Both total lymphocyte count and its composition were recorded at three timepoints:right before the radiation treatment(T0);immediately after the last fraction of radiotherapy(T1)and 6 months after irradiation therapy ended(T2).Results.Both groups experienced temporal lymphopenia after finishing local radiation(T1)(13F TO vs.T1 1570.6 ± 243.9 vs.940.6 ± 141.8,**p<0.01;25F TO vs.T1 1620.5 ± 280.2 vs.948.5 ± 274.6,**p<0.01),while the lymphocyte count recovered at follow-up time(T2),and the cell count in the hypofractionation group(13F)was higher than the standard fraction group(25F)(13F vs.25F 1725.6 ± 225.6 vs.1657.5 ± 242.4,*p<0.05).With respect to the composition of lymphocyte,we found T cell,B cell,and NK cell reacted differently to different radiotherapy protocols.Conclusions.Different RT protocols impose different impacts on immunity,leading us to further explore the optimal radiotherapy regimes to synergy with immunotherapy.