Effects of definitive and salvage radiotherapy on the distribution of lymphocyte subpopulations in prostate cancer patients.

Abstract

Radiotherapy (RT) is an established treatment for patients with primary and recurrent prostate cancer. Herein, the effects of definitive and salvage RT on the composition of lymphocyte subpopulations were investigated in patients with prostate cancer to study potential immune effects. Atotal of 33prostate cancer patients were treated with definitive (n= 10) or salvage RT (n= 23) after biochemical relapse. The absolute number of lymphocytes and the distribution of lymphocyte subpopulations were analyzed by multiparameter flow cytometry before RT, at the end of RT, and in the follow-up period. Absolute lymphocyte counts decreased significantly after RT in both patient groups and asignificant drop was observed in the percentage of Bcells directly after RT from 10.1± 1.3 to 6.0± 0.7% in patients with definitive RT and from 9.2± 0.8 to 5.8± 0.7% in patients with salvage RT. In contrast, the percentages of Tand natural killer (NK)cells remained unaltered directly after RT in both patient groups. However, 1year after RT, the percentage of CD3+ Tcells was significantly lower in patients with definitive and salvage RT. The percentage of regulatory Tcells was slightly upregulated in primary prostate cancer patients after definitive RT, but not after salvage RT. Definitive and salvage RT exert similar effects on the composition of lymphocyte subpopulations in prostate cancer patients. Total lymphocyte counts are lower in both patient groups compared to healthy controls and further decreased after RT. Bcells are more sensitive to definitive and salvage RT than Tand NK cells.