Abstract P3-10-01: Randomized phase III trial of taxanes versus S-1 as first-line chemotherapy for metastatic breast cancer (SELECT BC: CSPOR- MBC01)
Authors: Watanabe Takanori , Shimozuma Kojiro , Imi Kentaro , Doihara Hiroyoshi , Akabane Hiromitsu , Ueo Hiroaki , Ohno Shinji , Kashiwaba Masahiro , Fukuuchi Atsushi , Watanabe Kenichi , Tsuneizumi Michiko , Isaka Hirotsugu , Uemura Yukari , Ohashi Yasuo , Mukai Hirofumi 
Published: May 2015

Background: Treatment goals of metastatic breast cancer (MBC) are to prolong survival and improve health-related quality of life (HRQOL). Current standard first-line chemotherapy for MBC are the taxanes or anthracyclines; however treatment-related adverse events greatly reduce HRQOL. S-1 is an oral 5-fluorouracil derivative, and phase II trials showed good clinical efficacy and tolerability. We conducted a phase III randomized controlled trial to establish non-inferiority of S-1 in overall survival (OS) and superiority in HRQOL to taxanes, when given as first-line chemotherapy for MBC.

Methods: Patients with HER2-negative non-life-threatening MBC, naïve to chemotherapy for metastatic disease, were randomly assigned to the taxane or S-1 groups. In the taxane group, patients received docetaxel 60-75mg/m2 q3w, paclitaxel 80-100mg/m2 q1w, or paclitaxel 175 mg/m2 q3w according to institutional policy. In the S-1 group, patients received S-1 40–60 mg twice daily based on body surface area using a 28 days on;14 days off regimen. Treatment was repeated until tumor progression or for at least 6 cycles (taxane) or 4 cycles (S-1). After failure of the first-line protocol therapy, another cytotoxic agent was administered, based on the investigator’s discretion. HRQOL was assessed with the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30, the Patient Neurotoxicity Questionnaire (PNQ) and the EQ-5D at baseline and 3, 6, 12 months after the start of the treatment. The primary endpoint was OS. Secondary endpoints were time to treatment failure (TTF), adverse events, and HRQOL.

Results: A total of 618 women were enrolled. After a median follow-up of 34.6 months, median OS was 37.2 months in the taxane group (n=309) and 35.0 months in the S-1 group (n=309) (hazard ratio [HR] 1.05, 95% confidence interval [CI] 0.86–1.27, non-inferiority test p=0.015). Median TTF was 8.9 months in the taxane group and 8.0 months in the S-1 group (HR 1.10, 95% CI 0.93–1.30, p=0.022). The incidence of the following grade 3-4 adverse events, allergic reaction, edema and sensory neuropathy, were statistically significantly more frequent in the taxane group (p=0.038, 0.0013 and 0.0077, respectively). Hematologic and non hematologic toxicities except above did not differ significantly between the two groups. The results of the EORTC QLQ-C30 under study treatment indicated that the S-1 was better than the taxanes in global health status/QOL (p=0.044), physical functioning (p=0.002), role functioning (p=0.002), emotional functioning (p=0.004), cognitive functioning (p=0.026), social functioning (p&lt;0.0001), pain (p=0.042) and financial difficulties (p=0.003). EQ-5D utility scores were significantly higher in the S-1 group (p=0.033) during the first year. PNQ sensory and motor scores were significantly better in the S-1 group (p&lt;0.0001 and p=0.0002, respectively).

Conclusions: This study clearly demonstrated that S-1 was superior to taxanes in terms of HRQOL and toxicity, without compromising the prolonged OS. S-1 should be considered as a new standard for first-line chemotherapy for MBC. We are conducting another similar trial (UMIN000005449) that compares first-line anthracycline with S-1 in terms of OS and HRQOL.

Citation Format: Takanori Watanabe, Kojiro Shimozuma, Kentaro Imi, Hiroyoshi Doihara, Hiromitsu Akabane, Hiroaki Ueo, Shinji Ohno, Masahiro Kashiwaba, Atsushi Fukuuchi, Kenichi Watanabe, Michiko Tsuneizumi, Hirotsugu Isaka, Yukari Uemura, Yasuo Ohashi, Hirofumi Mukai. Randomized phase III trial of taxanes versus S-1 as first-line chemotherapy for metastatic breast cancer (SELECT BC: CSPOR- MBC01) [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-10-01.