Background/Objectives: An anastomotic leak (AL) following colorectal surgery is one of the most feared complications due to its associated morbidity and mortality. Early detection of ALs remains difficult, as the development of clinical signs of deterioration can be a late finding. This is particularly problematic in patients with poor access to care after discharge. C-reactive protein (CRP) is a systemic marker of inflammation that has been proposed as an early AL screening. However, absolute cut-off values have been shown to have limited sensitivity and specificity. We propose the use of CRP trends for early AL detection. Methods: A retrospective chart review of patients undergoing surgery requiring at least one anastomosis at a single tertiary care center was performed. Patients with two or fewer postoperative CRP values were excluded. Postoperative CRP trends were compared between control and AL patients using a mixed model with a Geisser–Greenhouse correction. Results: CRP trends differed significantly between AL and control patients, with a 10% CRP increase after postoperative day two showing 100% sensitivity and 84% specificity for an AL as well as a 100% negative predictive value. Accepted CRP cut-off values on postoperative days three and four had sensitivities of only 71.4% and 80% and specificities of 70.0% and 76.5%, respectively. CRP trends differed in AL versus control patients despite the surgical approach or presence of additional procedures. Conclusions: Daily monitoring of CRP trends (versus absolute cut-offs) may enhance early anastomotic leak detection and aid in discharge decision-making, particularly important in rural settings with limited healthcare access.

Background: Circulating tumor DNA (ctDNA) is extracellular DNA released by tumors and has been proposed as a marker of residual disease as well as a predictor of disease recurrence in the adjuvant setting. However, data are lacking on the utility of this biomarker in the neoadjuvant setting. Methods: We performed a retrospective study of stage III and IV colorectal cancer patients receiving neoadjuvant treatment at a single institution. Results: Seventeen patients converted from a positive pre-neoadjuvant ctDNA to a negative ctDNA prior to surgery. Five patients remained persistently positive despite systemic treatment. ctDNA conversion was found to be associated with a higher incidence of favorable treatment effect scores on final surgical pathology. There was no difference in recurrence-free survival in this small population. Furthermore, no added benefit was identified for patients receiving additional neoadjuvant therapy after the time of positive to negative ctDNA conversion. Conclusions: This study highlights the potential utility of ctDNA and the need for prospective trials in the neoadjuvant setting to monitor treatment response and guide decisions on treatment duration.