97P Efficacy and safety of the fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection in patients with HER2-positive early breast cancer: Long-term data from the PHranceSCa study

In the phase II PHranceSCa study (NCT03674112), 85% of patients preferred the fixed-dose combination of pertuzumab (P) and trastuzumab (H) for subcutaneous injection (PH FDC SC) over PH infused intravenously (IV) as adjuvant treatment for HER2-positive early breast cancer, with no new safety signals with PH FDC SC. We present efficacy and safety data after continuation of treatment and follow-up. Patients with locally advanced, inflammatory, or early breast cancer who had completed neoadjuvant PH + chemotherapy and surgery were randomised 1:1 to 3 cycles of PH FDC SC (600 mg P/600 mg H in 10 mL) followed by 3 cycles of PH IV (P 420 mg; H 6 mg/kg) or 3 cycles of PH IV followed by 3 cycles of PH FDC SC. If needed, loading doses were P 1200 mg /H 600 mg in 15 mL for PH FDC SC and P 840 mg/H 8 mg/kg for PH IV. After the crossover period, patients continued treatment by their preferred method (continuation period, up to 18 cycles total). Efficacy (invasive disease-free survival [IDFS]) and overall survival (OS), safety and quality of life (EORTC QLQ-C30) were assessed after 3 years. 159/160 patients were treated in the continuation period (138 PH FDC SC, 21 PH IV, median 8 cycles for both) and 148 completed follow-up. The table shows safety in the continuation period. Most adverse events (AEs), including all cardiac AEs (n = 2) and anaphylaxis/hypersensitivity (n = 2), were grades 1/2. No grade 4/5 AEs occurred. There were six IDFS events (3.8%: 3-year IDFS 97.4%, 95% confidence interval [CI] = 94.9, 99.9) and two deaths (1.3%: 3-year OS 98.7%, 95% CI = 96.9, 100.0). Mean changes from baseline in EORTC QLQ-C30 were generally minimal. PH FDC SC was well tolerated, with safety consistent with that of PH IV (except injection-site reactions) and no grade ≥3 anaphylaxis/hypersensitivity or new safety signals in the continuation period. Efficacy data are immature but show high IDFS and OS rates at 3 years.