Effect of acid-reducing agents on the efficacy of capecitabine in metastatic gastrointestinal cancers.

Abstract

e15058 Background: Recent retrospective and subgroup analyses have evaluated the effects of capecitabine with acid-reducing agents both in the adjuvant setting for colon cancer and in the palliative setting for stage IV gastroesophageal malignancies. Efficacy outcomes in these studies are contradictory. Acid-reducing agents are thought to reduce the absorption of capecitabine by increasing gastric pH leading to a concern of decreased efficacy. Studies thus far have not included stage IV colorectal cancers, a common population who receives capecitabine-based regimens. Methods: We conducted a retrospective chart review of patients diagnosed with stage IV Gastro Intestinal (GI) cancers treated with capecitabine-based therapies between 2012 and 2018. Electronic health records were used for data collection. Descriptive statistics and COX regression model were utilized for data analysis. Results: Of the 249 charts that were screened for inclusion, 58 were included in this review. Thirty-eight (65.5%) had a diagnosis of colon cancer, 11 (19%) had rectal cancer, and 9 (15.5%) had other GI malignancies. The most common capecitabine-based regimens included XELOX alone (29%) or with bevacizumab (36%). During capecitabine treatment, 20 (34.5%) patients received concomitant acid-reducing therapy. This included 19 patients taking a PPI and 1 patient taking a H2 Inhibitor. Patients who did not receive acid-reducing therapy had a 1-year PFS of 23.7% compared to 25% in patients who did not, (HR 0.55, p = 0.46). The 1-year OS was 68.4% in the non-acid-reducing agent group and 60% in the patients who did receive acid-reducing agents during capecitabine treatment, respectively (HR 0.17, p = 0.68). Conclusions: Receiving acid-reducing agents concomitantly with capecitabine-based regimens appears to not have an effect on 1-year PFS or OS in patients with Stage IV GI cancers. These outcomes may have been affected by the sample size, incomplete home medication lists, and compliance issues with capecitabine. Larger population studies are needed to validate these findings and identify the significance of utilization of acid-reducing agents in patients with Stage IV GI cancers receiving capecitabine.