Abstract CT025: Phase I trial of selenium plus chemotherapy in gynecologic cancers

PURPOSE: The effectiveness of standard-of-care platinum-taxane chemotherapy in the treatment of patients with advanced gynecologic cancers is limited by the development of chemotherapy resistance in nearly all patients. Based on our preclinical findings that selenium, an essential trace element, inhibits the development of carboplatin drug resistance in an ovarian cancer mouse model, a phase I trial of a combination of selenious acid/carboplatin/paclitaxel was designed to determine the maximum tolerated dose (MTD) and safety of selenium administered with chemotherapy in chemo-naive women with gynecologic cancers. In addition, the effects of selenium on carboplatin pharmacokinetics were evaluated in this group of patients, and correlative studies were performed to identify potential gene targets of selenium. METHODS: Patients with gynecologic malignancy not previously treated with chemotherapy received 50-5000 µg elemental selenium IV in the form of selenious acid on day 1 followed by carboplatin (cycle 1, AUC 5; subsequent cycles, AUC 6) IV and paclitaxel 175mg/m2 IV on day 3. A standard 3+3 trial design was used in the selenium dose escalation phase. Concentrations of selenium in plasma and carboplatin in plasma ultrafiltrate were analyzed. RNA expression in tumor specimens and breast and ovarian cancer cell lines were compared before and after treatment with selenium plus chemotherapy using the Human Exon 1.0 ST exon microarray platform. In addition, Western immunoblotting was performed to evaluate protein expression of RAD51AP1, a protein involved in DNA repair, in untreated MCF-7/Adr cells and MCF-7/Adr cells treated with selenium, carboplatin, and the combination of selenium and chemotherapy. RESULTS: Forty-five patients were enrolled and a total of 291 treatment cycles were administered. Grade 3/4 toxicities included neutropenia (66.6%), febrile neutropenia (2.2%), as well as pain (20.0%), infection (13.3%), neurologic (11.1%), and pulmonary adverse effects (11.1%). The MTD of elemental selenium was not reached. Selenium had no effect on carboplatin pharmacokinetics. In the subset of patients with stage III/IV ovarian cancer/fallopian tube/peritoneal cancer, median progression-free survival was 15 months; in those patients within this subset with measurable disease, 30%, 35%, and 23% experienced complete response, partial response, and stable disease, respectively. Correlative studies showed downregulation of RAD51AP1 by selenium plus chemotherapy in cancer cell lines as well as in tumors of patients treated within this clinical trial. CONCLUSION: Selenium in combination with carboplatin and paclitaxel is safe and does not affect carboplatin pharmacokinetics. It is possible that selenium-mediated downregulation of RAD51AP1 plays a role in circumventing the development of resistance to carboplatin/paclitaxel chemotherapy. A phase II study to further investigate these findings is underway. Citation Format: Mihae Song, Muthu N. Kumaran, Murugesan Gounder, Darlene Gibbon, Wilberto Nieves-Neira, Ami Vaidya, Mira Hellman, Michael P. Kane, Brian Buckley, Lorna Rodriguez-Rust. Phase I trial of selenium plus chemotherapy in gynecologic cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT025.