Changes in platelet/lymphocyte ratio after CRT to predict oncologic outcome in patients with rectal cancer.

Abstract

539 Background: Previous studies have shown that the neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) are potential prognostic markers in many different cancers. However, the relationship between the changes of these ratios after concurrent chemoradiotherapy (CRT) and clinical outcome in rectal cancer patients was not reported yet. Accordingly, the aim of this study was to evaluate the prognostic relevance of the changes in NLR and PLR in patients with rectal cancer who treated with CRT followed by surgery. Methods: We enrolled 296 patients with histologically confirmed rectal adenocarcinoma who have received preoperative CRT at Kyungpook National University Medical Center (Daegu, Korea) between January 2006 and December 2015. We analyzed full hematological data both pre CRT (initial visit) and post CRT (before surgery) and oncologic outcomes including pathologic complete response (pCR), relapse-free survival (RFS), and overall survival (OS). An NLR≥5 and PLR ≥235 were considered to cut-off values according to previous studies. The ratio of change in NLR and PLR were calculated by following formula: ratio of change in NLR = (post NLR-pre NLR)/ pre NLR *100, ratio of change in PLR = (post PLR-pre PLR)/pre PLR *100. Significant cut-off value for ratio of change in NLR and PLR were calculated by simulation analysis (SAS Institute Japan, Tokyo, Japan). Results: Of the 296 patients, the majority were male (69.6%), with a median age of 59.1 years (range 25~88). Of these patients, 41 (13.9%) obtained pCR after CRT. Sixty-one patients (20.6%) had high PLR before CRT, which significantly correlated with pCR (p = 0.014) and RFS (p = 0.026), while high NLR was associated with pCR (p = 0.012) only. The optimal cut-off value for the ratio of change in PLR was 200 for RFS. The patients who had relatively higher ratio of change in PLR (ratio of change in PLR ≥ 200) showed better RFS compared to lower ratio of change (ratio of change in PLR < 200) (3-year RFS 90.9% vs. 69.7%, p = 0.05). Changes in NLR did not correlate with oncologic outcomes. Conclusions: Changes in platelet/lymphocyte ratio could also be a potential clinical biomarker in predicting oncologic outcome in rectal cancer patients treated with preoperative CRT.