Original article Comparative analysis of the effects of radiotherapy versus radiotherapy after adjuvant chemotherapy on the composition of lymphocyte subpopulations in breast cancer patients Eva K. Sage a,1 , Thomas E. Schmid a,b,c,1 , Michael Sedelmayr a , Mathias Gehrmann a , Hans Geinitz d , Marciana N. Duma a,b , Stephanie E. Combs a,b,c , Gabriele Multhoff a,b,c,⇑ a Department of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München (TUM); b HelmholtzZentrum München, Department of Radiation Sciences (DRS), Institute of Innovative Radiotherapy (iRT); c Deutsches Konsortium für Translationale Krebsforschung (DKTK), Partner Site Munich, Germany; and d Department of Radiation Oncology, Krankenhaus der Barmherzigen Schwestern and Medical Faculty, Johannes Kepler University Linz, Austria article info Article history: Received 2 September 2015 Received in revised form 11 November 2015 Accepted 16 November 2015 Available online xxxx Keywords: Breast cancer Radiotherapy Chemotherapy Lymphocyte subpopulations abstract Background: Breast cancer is the most common cancer in women worldwide and surgery, radiotherapy (RT) and chemotherapy (ChT) are frequently used to treat this cancer. Adjuvant RT has been shown to cause long-term changes in lymphocyte counts in the peripheral blood. Herein, the time course of changes in lymphocyte subpopulations upon RT was studied in patients with and without adjuvant ChT in order to explore its potential clinical impact. Materials and methods: Total lymphocyte counts and the composition of lymphocyte subpopulations before RT (t0), after 30 Gy (t1), at the end of RT (t2), and 6 weeks (t3), 6 months (t4), and 1 year (t5) after RT were studied by flow cytometry. Results: Absolute lymphocyte counts were significantly lower in all breast cancer patients (n = 40) before and also 1 year after RT compared to healthy controls. The percentage of CD3 + /CD4 + helper T cells and FoxP3 + regulatory T cells increased significantly in patients without adjuvant ChT. Different NK cell sub- populations dropped during RT in patients with and without ChT, but recovered to initial levels 6 months after RT (t4). During RT (t0–t2) the percentage of CD19 + B cells significantly dropped in patients without ChT, but gradually increased in patients with adjuvant ChT. Both patient groups reached initial levels 6 months after RT (t4). Conclusion: Different lymphocyte subpopulations respond differently to RT with and without adjuvant ChT. CD4 + T cells increase during RT, whereas NK cells and B cells decrease in patients without ChT, but recover within 6 months after RT. Treg cells gradually increase in patients without ChT from t0 to t5, but not in patients with adjuvant ChT. Ó 2015 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology xxx (2015) xxx–xxx Breast cancer is the most common cancer in females worldwide with approximately 1.7 million newly diagnosed cases in 2012 (World Cancer Research Fund). Postoperative radiotherapy (RT) that is given to abolish remaining tumor stem cells after surgical resection is one of the most important treatment options to improve local tumor control and overall survival in breast cancer patients [1]. Although the main effect of RT is the direct killing of tumor cells, non-targeted radiation effects that can modulate antitumor immune responses may also affect clinical outcome. Different mechanisms are presently discussed that impair white blood cell counts and affect the composition of lymphocyte sub- populations. Stjernsward et al. [2] described long-term changes in lymphocyte counts induced by RT of breast cancer patients and related those to tumor responses. Immune effects have been shown to influence clinical outcome and prognosis [3]. Cho et al. claim that the nadir of lymphocyte counts has prognostic value in patients with head and neck cancer [4], while others have shown that white blood cell counts and serum markers did not correlate with prognosis in breast cancer patients treated with surgery, RT and ChT [5]. Varying numbers of dendritic cells (DCs), regulatory T cells, and tumor infiltrating lymphocytes (TILs) in patients suffer- ing from head and neck [6] or colorectal cancer [7] have been described to have prognostic value and a correlation of these cell types and tumor stage was found in gastric or colorectal carcinoma patients [8,9]. http://dx.doi.org/10.1016/j.radonc.2015.11.016 0167-8140/Ó 2015 Elsevier Ireland Ltd. All rights reserved. ⇑ Corresponding author at: Experimental Radiation Oncology/Biology, Depart- ment of Radiation Oncology, Klinikum rechts der Isar, Technische Universität München (TUM), Ismaningerstr. 22, 81675 Munich, Germany. E-mail address: gabriele.multhoff@tum.de (G. Multhoff). 1 Both authors contributed equally. Radiotherapy and Oncology xxx (2015) xxx–xxx Contents lists available at ScienceDirect Radiotherapy and Oncology journal homepage: www.thegreenjournal.com Please cite this article in press as: Sage EK et al. Comparative analysis of the effects of radiotherapy versus radiotherapy after adjuvant chemotherapy on the composition of lymphocyte subpopulations in breast cancer patients. Radiother Oncol (2015), http://dx.doi.org/10.1016/j.radonc.2015.11.016