Detrimental immunologic effects of preoperative chemoradiotherapy in advanced rectal cancer

Preoperative chemoradiotherapy for advanced rectal cancer has been an important therapeutic tool to improve the long-term results of curative resection. It is not known whether preoperative chemoradiotherapy for advanced rectal cancer influences the perioperative course of immune parameters.

Thirty patients with rectal cancer underwent surgery with (study group, n = 15) or without (control group, n = 15) preoperative chemoradiotherapy (2 cycles of 5-fluorouracil, 45 Gy). Blood samples were taken before neoadjuvant therapy, preoperatively, and on Days 1, 2, and 5 after surgery. Cell numbers of lymphocyte subpopulations, granulocytes, monocytes, and natural killer cells were determined by flow cytometry; tumor necrosis factor-alpha and interleukin-6 serum levels were measured with enzyme-linked immunosorbent assay.

Significant differences between study and control patients (P < 0.05) were detected regarding circulating interleukin-6 and tumor necrosis factor-alpha levels, with depression of the proinflammatory response to surgery in study patients. Similarly, granulocytosis and monocytosis after surgery were significantly lower in patients after neoadjuvant therapy. Furthermore, cell counts of total T lymphocytes, T helper cells, B lymphocytes, and natural killer cells were significantly reduced after preoperative chemoradiotherapy. This depression of cell-mediated immunity in study patients was even more pronounced after surgery.

Preoperative chemoradiotherapy for advanced rectal cancer results in a significant preoperative and postoperative immune dysfunction as indicated by depression of lymphocyte subpopulations, monocytes, granulocytes, and proinflammatory cytokine release. These findings are of importance because increased perioperative morbidity and mortality rates have been observed after preoperative chemoradiotherapy.