Abstract P1-15-21: Safety of eribulin mesylate and concomitant palliative radiotherapy for metastatic breast cancer: A single-center experience

Abstract

Abstract Background. Eribulin mesylate is a recently approved new therapeutic option for patients with metastatic breast cancer (BC). It is a structurally simplified synthetic analogue of halichondrin B that inhibits the growth phase of microtubule dynamics and sequesters tubulin into non-productive aggregates, inhibiting microtubule polymerization, and inducing irreversible mitotic block at G2-M phases and apoptosis. Three phase II trials of eribulin in chemotherapy pretreated advanced BC patients were completed. In all these studies, eribulin showed a manageable tolerability profile, with most of the common drug-related adverse events being neutropenia, fatigue, alopecia, nausea, and anemia, according to the phase I trials findings. Eribulin was also associated with an overall low incidence of peripheral neuropathy. When new chemotherapy options become available, one of the most important questions regarding the sequence of treatments is to address the safety of concomitant radiation treatments. Recently has been reported a clinical case treated with eribulin mesylate and whole-brain radiotherapy (RT) in a heavily pretreated patient with multiple visceral and bone metastases from triple negative breast cancer. In our knowledge this is the first analysis focusing on the safety of eribulin in patients concomitantly treated with palliative RT. Methods. All patients where heavily pretreated for metastatic breast cancer (≥4 previous chemotherapy lines), including anthracyclines and taxanes-based regimens. Patients received eribulin mesylate (1.4 mg/m2 i. v., on days 1 and 8, of a 21-day cycle). Tumor response was assessed using the Response Evaluation Criteria in Solid Tumors (RECIST), every 8 weeks, or sooner if disease progression was suspected. Safety was assessed according to National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 4.0. Measures of bone-pain scores and analgesic consumption were evaluated at each visit, using a patient-rated scoring system. Results. Concerning 25 consecutive treated patients, median performance status at baseline was 2 (range 1-3). A median of 4 cycles of eribulin (range 2-10) were administered. All patients received palliative bone RT during eribulin treatment. No suspension or delay in chemotherapy administration was necessary. 20/25 cases underwent spinal bone irradiation; 8 Gy in single fraction was given in 13/25 patients, 12 cases received 20 Gy in 5 fractions. The overall response rate was 24% and the clinical benefit rate was 40%. Toxicity was manageable and in line with main published series; the most frequent grade 3 hematologic adverse events were neutropenia (56%), and anemia (20%). Bone pain scores fell within a few weeks and remained below baseline value throughout the analysis. The mean pain score was 2 at baseline and 0.7 at the end of observation period. The mean analgesic score was 1.8 at baseline and 1.6 at the end of follow-up. Conclusions. Our clinical practice experience supports the evidence that eribulin has clinical activity and is characterized by a manageable safety profile, also when combined to palliative RT. Concomitant treatment is feasible also in patients heavily pretreated, and with poor performance status. Citation Format: Icro Meattini, Vieri Scotti, Carla De Luca Cardillo, Beatrice Detti, Vanessa Di Cataldo, Lorenzo Livi. Safety of eribulin mesylate and concomitant palliative radiotherapy for metastatic breast cancer: A single-center experience [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 P1-15-21.