Impact of concomitant acid suppressive therapy on pazopanib efficacy and dose reductions in patients with metastatic renal cell carcinoma.

The aim of this study was to investigate the impact of acid suppressive therapy on clinical efficacy and safety of pazopanib in patients with metastatic renal cell carcinoma (mRCC). A single-center retrospective study was carried out. Charts of mRCC patients who received pazopanib as first-line treatment were reviewed and concomitant use of proton pump inhibitors (PPI) and histamine 2 receptor antagonists (H2RA) was studied. Two groups of patients were identified, namely patients receiving PPI/H2RA and patients without acid suppressive therapy. Both groups were compared with regard to progression free survival (PFS), overall survival (OS), tumor response, and time to dose reduction of pazopanib. Ninety-one patients were included. Median PFS was 8 months in the PPI/H2RA group vs. 7 months in the no PPI/H2RA group (hazard ratio (HR) 0.76 (95% confidence interval (CI) 0.42-1.35)), p = 0.35. Median OS was 27 months in the PPI/H2RA group vs. 23 months in the no PPI/H2RA group (HR 0.87 (95% CI 0.46-1.66)), p = 0.68. Mean tumor response was 17% (95% CI 8-25%) in the PPI/H2RA group vs. 11% (95% CI 0-21%) in the no PPI/H2RA group, p = 0.52. Median time to first dose reduction was 9 months in both subgroups (HR 1.25 (95% CI 0.65-2.39)), p = 0.51. Median time to second dose (< 600 mg) reduction was 17 months in the PPI/H2RA group vs. 7 months in the no PPI/H2RA group (HR 0.26 (95% CI 0.07-0.89)), p = 0.03. In this limited patient series, no evidence of a negative impact of PPI/H2RA on clinical outcome and time to first dose reduction was observed. These results suggest that PPI/H2RA might be considered, when there is a clinical need, in patients treated with pazopanib for mRCC. However, a prospective study is warranted to confirm these results.