Original Article Does gastric acid suppression affect sunitinib efficacy in patients with advanced or metastatic renal cell cancer? Vincent H Ha 1,2, *, Margaret Ngo 2,3, *, Michael P Chu 4 , Sunita Ghosh 5 , Michael B Sawyer 4 and Carole R Chambers 1 Abstract Introduction: Renal cell cancer is a chemotherapy-insensitive cancer treated by vascular endothelial growth factor receptor antagonists. Recently, a question has arisen on whether there is an interaction between tyrosine kinase inhibitors, such as sunitinib, and acid suppressing agents. Methods: A retrospective chart review was conducted for patients at two tertiary care centers who received sunitinib between 1 January 2006 and 31 March 2013. Using electronic systems and a province-wide electronic health records database, medication dispensing records were obtained. A univariate Cox’s proportional hazard model determined if acid suppression had effects on progression-free survival and overall survival. Results: Of 383 patient charts reviewed, 231 were included in the study. Patients on intermittent acid suppression, lost to follow-up or received sunitinib for less than one week were excluded from the study. The median age of the study population was 65. Patients who received no acid suppression (n ¼ 186) had a median progression-free survival of 23.6 weeks (95% CI, 19.0–31.9 weeks) and patients who received continuous acid suppression (n ¼ 45) had a median progression-free survival of 18.9 weeks (95% CI, 11.0–23.7 p ¼ 0.04). A median overall survival of 62.4 weeks (95% CI, 42.0–82.7 weeks) was observed in the group with no acid suppression, while a median overall survival of 40.9 weeks (95% CI, 26.1–74.4 weeks) was observed in the continuous acid suppression group (p ¼ 0.02). Conclusion: There was a significant difference in progression-free survival and overall survival between the acid sup- pressed and no acid suppression groups. Further research is required to confirm this potential interaction. Keywords Sunitinib, proton pump inhibitors, renal cell cancer, progression-free survival, overall survival Introduction Renal cell cancer (RCC) is a common cancer which is estimated to affect 5900 Canadians in 2013. 1 RCC was one of the most chemotherapy-insensitive forms of cancer until development of vascular endothelial growth factor receptor (VEGFR) antagonists. Over the last few years, VEGFR antagonist tyrosine kinase inhibitors (TKIs), such as sunitinib and sorafenib, have become first-line agents for treating metastatic RCC (mRCC). However, a recent review article has ques- tioned whether there is a significant interaction between TKIs and acid suppressing agents. 2 With TKIs being fairly new to the clinic, interactions between TKIs and acid suppressing agents have scarcely been studied and are not documented in interaction databases such as Medscape, LexiComp and Micromedex Õ . 3–5 1 Pharmacy Department, Cross Cancer Institute, Canada 2 Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Canada 3 Pharmacy Department, Tom Baker Cancer Centre, Canada 4 Department of Medical Oncology, Cross Cancer Institute, Canada 5 Experimental Oncology Department, Cross Cancer Institute, Canada *Vincent H Ha and Margaret Ngo equally contributed in collecting the data and writing the manuscript Corresponding author: Michael B Sawyer, Department of Medical Oncology, Cross Cancer Institute, 11560 University Avenue, Edmonton, AB T6G 1Z2, Canada. Email: Michael.Sawyer@albertahealthservices.ca J Oncol Pharm Practice 2015, Vol. 21(3) 194–200 ! The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/1078155214527145 opp.sagepub.com