Inclusion and exclusion criteria
Patients who underwent elective, potentially curative resection for colorectal neoplasia in our institution, the Mater Misericordiae University Hospital, between January 2009 and December 2016 were included for analysis. Cases of dysplastic tumors were also included and adjusted for in the analysis. Patients with second cancers and inflammatory bowel disease and those that underwent neoadjuvant chemotherapy or radiation therapy were excluded from the study, in addition to those admitted with fever or overt sepsis. Patients without any laboratory data or postoperative outcome documentation were excluded from analysis, while those with incomplete datasets were included in the relevant subcategory analysis only.
Patient management
Patients planned for elective surgery in our institution routinely complete a full diagnostic work-up, which includes computerized tomography of the chest, thorax and abdomen for staging as well as clinical review by senior members of the surgical service, gastroenterology, and general medicine. Following diagnostic work-up, patients attend a preoperative assessment clinic where they are examined by a senior member of the anesthetic and critical care service. Hematological and biochemical testing and, when indicated, electrocardiography and echocardiography are also completed. Results are reviewed and patients with treatable co-morbidity are triaged for specific clinical care. Those with normal investigations, those with abnormal blood tests without overt clinical correlate (and so without ready correction), and those with conditions that cannot be further optimized but whom are judged suitable for operation all proceed to surgery.
Data interpretation
The blood profiles of patients reviewed for this study were obtained within the time period after diagnosis and before the operation. All patients routinely have FBC measured while some have CRP and carcinoembryonic antigen (CEA) checked as part of their oncological staging and general work-up. The inflammatory markers included for analysis are CRP, white blood cell count (WBC), platelets, neutrophils, lymphocytes, platelets-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte ratio (NLR). Hemoglobin (Hb) was also included. Other patient-related factors recorded were age, gender, body mass index, and smoking status. Preoperative comorbidities recorded include diabetes in addition to any defined cardiovascular, respiratory, renal and/or autoimmune disease known to preexist or detected on work-up. Surgical technique was classified as laparoscopic or open, the latter including conversions to open. Tumor site was classified into right-sided (cecum, ascending, and transverse), left-sided (descending and sigmoid), and rectal. In patients with malignant tumors, pathological tumor stage, nodal status and differentiation were recorded.
All 30-day postoperative outcomes and management were recorded prospectively for departmental audit, including categorization into affected system (i.e. respiratory, urinary, neurological, cardiovascular) and Clavien-Dindo classification grading to signify complication severity. Various systemic and surgical site complications were recorded. Systemic complications include thromboembolism, urinary, renal, respiratory, cardiovascular, and neurological complications. Surgical site complications, both superficial and deep, include ileus, anastomotic leakage, and wound infection, dehiscence or herniation.
Statistical techniques
Continuous variables were presented as means with their standard deviations (σ) in tabular form. Preoperative and intraoperative values were transformed into categorical variables. For example, inflammatory markers were classified as normal or abnormal according to standard laboratory values. Though we used a cut-off of above 5 mg/L to denote CRP elevation, we also ran regression analysis using a cutoff of 10mg/L to assess the validity of this threshold as used in the mGPS scoring system. Univariable analysis was performed using chi square analysis or Fisher’s exact test where appropriate, with these variables examined against all listed postoperative complications and Clavien-Dindo grades. Multivariable analysis included only variables scoring p ≤ 0.25 in the univariable analysis, and was performed using binary logistic regression analysis and expressed as odds ratios (OR). A ROC curve was plotted of CRP against a) the presence and b) the severity of a postoperative complication. Optimal cut-off values of CRP were determined using the Youden index. All analyses were performed using SPSS (SPSS, Version 20. Armonk, NY). Results were considered statistically significant where the two-tailed p-value was less than 0.05.