Serum bicarbonate is a marker of peri-operative mortality but is not associated with long term survival in colorectal cancer

AIMS: Inflammation is a hallmark of cancer whose activity is modulated within the tumor microenvironment by low tumoral pH. Recent evidence in the literature has suggested a link between low serum bicarbonate, low tumoral pH and cancer related inflammation. There is however little clinical evidence in human patients regarding the prognostic role of serum bicarbonate. Therefore, the primary aim of this study was to investigate the short and long-term prognostic utility of serum bicarbonate in colorectal cancer (CRC) patients undergoing resection of their primary tumor. The study also aimed to investigate the association of serum bicarbonate with known markers of systemic inflammation. METHODS: A total of 3281 consecutive patients who underwent surgical resection of their primary CRC from January 1998 to December 2012. Of these, 2223 stage I-IV patients had available data for analysis. The association of serum bicarbonate with overall survival was assessed using univariate and multivariate cox regression analyses. The association of bicarbonate with other clinicopathological variables was assessed by chi squared and Fisher’s exact tests. RESULTS: Serum bicarbonate was associated with peri-operative mortality in multivariate analysis (p<0.001). Age (p = 0.004), grade (p = 0.043), creatinine (p = 0.036) and sodium (p = 0.036) were also markers associated with peri-operative mortality. For long term survival at 5 years, bicarbonate was significantly associated with overall survival in univariate analysis (p<0.001) but was not significant in multivariate analysis (p = 0.075). In exploratory analysis, serum bicarbonate was found to be significantly associated with the lymphocyte-to-monocyte ratio (p<0.001) and neutrophil-to-lymphocyte ratio (p<0.001). CONCLUSIONS: In peri-operative colorectal cancer patients, serum bicarbonate was associated with 30-day survival but not 5-year survival.