Eribulin-trastuzumab combination in HER2-positive metastatic breast cancer: updated results from a Russian observational study

Introduction . The standard of 1st line treatment of HER2+ metastatic breast cancer (mBC) is double blockade with trastuzumab and pertuzumab + taxane, 2nd line – Trastuzumab-emtazine. There are no standards for further treatment, as well as the optimal drug sequence. Expansion of the arsenal of therapeutic possibilities and the use of new combinations will certainly improve the results of treatment of this category of patients and increase their life expectancy. Aim . We sought to describe treatment patterns of eribulin and clinical outcomes of metastatic HER2-positive breast cancer treated with eribulin plus trastuzumab combination in academic institutions and community oncology practices across the Russian Federation. Materials and methods . Patients treated with eribulin anytime between Jan, 2014 and Sep, 2019 with a diagnosis of MBC were identified by 23 providers from Russia. Providers retrospectively reviewed the health records and abstracted selected data points into an electronic case report form for each eligible patient. Results . 100 HER2-positive pts received eribulin in combination with trastuzumab. Median age was 55 (31–80) yrs and ECOG status 0–3. 67% pts had visceral metastases. Eribulin was administered as 1st and 2nd line to 23 (23%) pts, 3rd line to 31 (31%) pts, 4th line and later to 46 (46%). Median number of cycles was 5 (2–27). ORR was 12%, SD – 72%, SD > 6 months – 23%, PD – 16%. Clinical efficacy rate achieved in 35%. Median PFS was 5.07 months (95% CI 4.021–6.119). According to the ER-status the response to eribulin and trastuzumab was different. ORR was 18.8%, SD 72.9% in pts with ER-positive MBC (n = 48) and 5.8% and 71.2% respectively in ER-negative MBC (n = 52). Median PFS was 6.97 months (95% CI 3.924–10.016) in pts with ER-positive MBC and 4.67 months (95% CI 3.841–5.499) in ER-negative MBC (р = 0.3). The combination was well tolerated: dose reductions were required in 12% pts, withdrawal due to toxicity in 4% pts. The most common type of toxicity was hematological with neutropenia Gr III-IV in 14 (14%) pts. Peripheral neuropathy Gr III was observed in 5 (5%) pts. No cardiotoxicity was detected. Conclusions . This is the real-life data of clinical outcomes for patients receiving eribulin plus trastuzumab for HER2-positive MBC throughout the Russian Federation. Our experience with eribulin plus trastuzumab demonstrates that this combination may be a potential effective treatment option for HER-2 positive MBC patients.