Effect of antacid intake on the therapeutic efficacy of sunitinib (SUN) in metastatic renal cell carcinoma (mRCC) patients (pts): A sub-analysis of the STAR-TOR registry

Background Antacids (AA) are commonly used in the elderly population. Proton pump inhibitors and other drugs to neutralize the gastral pH level and to prevent gastroesophageal reflux are suspected to reduce the efficacy of tyrosine kinase inhibitors. To our knowledge, the effect of AA therapy on SUN efficacy has not been investigated in a real-world mRCC population yet. Methods STAR-TOR is a German multicenter registry for pts with mRCC (NCT00700258) which was amended to include SUN pts in June 2010 with regulatory and ethic committee’s approval. Objectives are the evaluation of the safety profile, the tolerability and anti-tumor activity of SUN. Here, we present data on the impact of AA therapy on the therapeutic efficacy of SUN in first-line mRCC pts. Results From July 2010 to February 2019, 109 active study sites recruited 550 first line SUN pts. 378 (69%)of these were reported to use AA therapy at baseline, 172 (31%) were AA non-users. Characteristics (AA yes/no): male 66.1/75.1%, median age 67.0/68.0 years, clear cell component: 81.4/81.5%. For all 550 pts, most common drug-related toxicities (incidence ≥ 15%) of any grade were gastrointestinal disorders (38.0%), general disorders including fatigue, mucosal inflammation and edema (29.1%), skin and subcutaneous tissue disorders including hand-foot syndrome (22.7%), nervous system disorders, and blood and lymphatic system disorders (both 19.1%). There was no relevant difference in adverse event rates between AA users and non-users. Efficacy (AA yes vs no): overall response rate 15.1 vs 27.4% (n = 426, p = 0.007), PFS 5.8 vs 8.0 months (mo), p = 0.11; OS 20.3 vs 25.7 mo, p = 0.01. Conclusions In our real-world data set, we found a relevant efficacy difference between SUN-treated first-line mRCC pts who used AA therapy at baseline compared with AA non-users, especially in terms of OS. This should be taken into account when prescribing SUN in this setting. Clinical trial identification NCT00700258. Legal entity responsible for the study Pfizer Pharma GmbH, Berlin, Germany. Funding Pfizer Pharma GmbH, Berlin, Germany. Disclosure K. Schlack: Advisory / Consultancy: Roche, Ipsen, Amgen, Novartis; Travel / Accommodation / Expenses: Bayer, Ipsen, Astellas, Takeda, Pfizer, Sanofi, Janssen-Cilag. M. Boegemann: Honoraria (self): Pfizer, Eisai, MSD, BMS, Ipsen, Eusa Pharma, Novartis. M. Woike: Full / Part-time employment: Pfizer Pharma GmbH. G. Krekeler: Full / Part-time employment: Pfizer Pharma GmbH. T. Fischer: Full / Part-time employment: Winicker-Norimed GmbH. L. Bergmann: Research grant / Funding (institution): BMS; Advisory / Consultancy: BMS, Eusa, Ipsen, Novartis, Pfizer, Roche. M. Rink: Advisory / Consultancy: BMS, Ipsen, MSD, Novartis, Pfizer, Roche. A. Strauss: Advisory / Consultancy: Bayer, MBS, Eisai, Novartis, Pfizer, Roche; Honoraria (self): Amgen, Bayer, BMS, Eisai, Ipsen, MSD, Novartis, Pfizer, Roche, Sanofi-Aventis; Travel / Accommodation / Expenses: Ipsen, Novartis. All other authors have declared no conflicts of interest.