Fecal calprotectin concentration to assess endoscopic and histologic remission in patients with cancer with immune-mediated diarrhea and colitis

BACKGROUND: Immune-mediated diarrhea and colitis (IMDC) is currently diagnosed and monitored by evaluating clinical symptoms. Deep remission is determined by endoscopic and histologic evaluation of the disease process. However, repeating these invasive procedures frequently can become cumbersome. We sought to assess the role of fecal calprotectin (FC) concentration as a non-invasive biomarker of endoscopic or histologic remission. METHODS: We performed a retrospective study of patients with IMDC who were tested for FC at IMDC onset and after IMDC treatment between June 2016 and March 2020. Patient demographics, clinical variables, and FC data were collected and analyzed to determine the optimal cut-off FC concentration to predict endoscopic and histologic remission. RESULTS: Our sample comprised 77 patients with a median age of 62 years; 66% were male and 94% were Caucasian. Sixty-five patients (84%) achieved clinical remission, 46 (60%) achieved endoscopic remission, and 24 (31%) achieved histologic remission after IMDC treatment. FC concentrations decreased from the time of IMDC onset to the end of treatment (p<0.001). High FC concentrations were associated with evident endoscopic inflammation (p=0.003) and acute/chronic active colitis (p=0.025) which positively correlated with the Mayo Endoscopic Subscore (r=0.615, p=0.001) at the time of IMDC onset. In patients who achieved endoscopic remission after treatment, a significantly lower FC concentration was observed at IMDC onset (p=0.006) and after treatment (p<0.001) compared with those without endoscopic remission. The cut-off FC concentration to predict endoscopic remission was ≤116 μg/g and for histologic remission ≤80 μg/g; these cut-offs had optimal specificity (94% and 85%, respectively) and positive predictive value (0.91 and 0.38, respectively). CONCLUSIONS: FC concentration may serve as a non-invasive biomarker to predict endoscopic and histologic remission in patients receiving treatment for IMDC, minimizing the need for frequent invasive endoscopies. Future prospective studies are needed to provide further insight on the role of this marker in disease surveillance.