Background: The aim of this prospective study was to evaluate the association between
lymphocyte subpopulation counts in the blood during preoperative chemoradiotherapy
(CRT) and tumor response in rectal cancer.
Methods: From August 2015 to June 2016, 10 patients satisfying criteria for prospective
study were enrolled. Patients received conventional radiotherapy with fluorouracil-based
chemotherapy and surgery was performed at 4 to 8 weeks after end of preoperative
CRT. The lymphocyte subpopulation was obtained prior to and after 4 weeks of
preoperative CRT. We analyzed the relationship between a tumor response and host
immunity such as lymphocyte subpopulation during preoperative CRT.
Results: Among 10 patients, 2 (20%) had evidence of pathologic complete response. In 8
patients with clinically node positive, 4 (50%) had nodal tumor response. All lymphocyte
subpopulation counts at 4 weeks after CRT were significantly lower than lymphocyte
count observed during pretreatment (p < 0.01). A high decrease in NK cell count during
CRT (baseline cell count − cell count at 4 weeks) was associated with node down
staging (p = 0.034).
Conclusions: Our results suggest that the change of lymphocyte subset to preoperative
CRT may be a predictive factor for tumor response in rectal cancer.
