S-1 Plus Standard Endocrine Therapy After Surgery for Breast Cancer
Posted: Tuesday, January 21, 2020
According to the results of the phase III POTENT trial, presented at the 2019 San Antonio Breast Cancer Symposium (Abstract GS1-09), the combination of the oral fluoropyrimidine-based drug S-1 plus standard endocrine therapy led to improved invasive disease–free survival and 5-year invasive disease–free survival in patients with hormone receptor–positive, HER2-negative breast cancer. Masakazu Toi, MD, PhD, of the Kyoto University Hospital, Japan, and colleagues concluded that their findings support this combination therapy in the postoperative adjuvant setting.
“Although we have made remarkable progress with systemic therapy for breast cancer, many patients still experience disease recurrence,” Dr. Toi said in an American Association for Cancer Research press release. “Because of the risk of recurrence, there is interest in identifying novel postoperative adjuvant therapies to be used in conjunction with endocrine therapy.”
In this open-label trial using S-1—a combination of the drugs tegafur, gimeracil, and oteracil—the investigators enrolled 1,939 patients from 139 centers in Japan. Patients were diagnosed with stage I to III hormone receptor–positive, HER2-negative breast cancer of intermediate or higher risk of recurrence. Patients received either S-1 plus endocrine therapy (957 patients) or endocrine therapy alone (973 patients).
After a median follow-up of 51.4 months, 101 patients treated with S-1 experienced disease recurrence (10.6%), compared with 155 patients treated with endocrine therapy alone (15.9%). Among those in the S-1 arm, the estimated 5-year invasive disease–free survival was 86.9%, versus 81.6% in the endocrine therapy–alone cohort.
The investigators reported that S-1 treatment was “tolerated and manageable.” The major toxicities experienced in this cohort included signs of bone marrow suppression, gastrointestinal adverse events, hyperpigmentation, and fatigue.
Disclosure: For full disclosures of the study authors, visit abstractsonline.com.
