Safety and effectiveness of eribulin in Japanese patients with soft tissue sarcoma including rare subtypes: a post-marketing observational study

Background: Soft tissue sarcomas (STSs) are a heterogeneous group of cancers with over 100 described subtypes. While these cancers are infrequent, the prognosis is quite poor, particularly for those with stage IV metastatic disease. Patients for whom curative resection is difficult or those with recurrent metastatic disease are treated with chemotherapy, although the options are very limited. Eribulin is an approved treatment of all STS subtypes in Japan. Efficacy and safety data for the treatment of rare STS subtypes other than liposarcoma and leiomyosarcoma (L-type sarcomas) are limited. This nationwide, multicenter, prospective, post-marketing observational study was conducted to assess the real-world effectiveness and safety of eribulin in Japanese patients with STS. Methods: Patients with all types of STS and who consented to eribulin treatment were eligible to participate. The observation period was 1 year, starting at treatment initiation, and clinical outcomes were followed up for 2 years after initiating treatment. The primary endpoint was overall survival (OS). Additional outcomes included time-to-treatment failure (TTF), objective response rate (ORR), disease control rate (DCR), and safety. ORR and DCR were evaluated using imaging findings. Effectiveness results were analyzed both for all patients and by STS subtype. Results: A total of 256 patients were enrolled; 252 and 254 were included in the effectiveness and safety analysis set, respectively. Most patients (83.1%) received an initial eribulin dose of 1.4 mg/m(2) (standard dose). Respective median OS (95% confidence interval [CI]) was 10.8 (8.5-13.1), 13.8 (10.1-22.3) and 6.5 (5.7-11.1) months for all, L-type, and non-L-type subtypes. The respective median TTF (95% CI) was 2.5 (2.1-2.8), 2.8 (2.3-3.7), and 2.2 (1.6-2.6) months. The ORR and DCR were 8.1 and 42.6%, respectively. Adverse drug reactions (ADRs) and serious ADRs were reported for 83.5 and 18.9% of patients, respectively. The main ADRs were associated with myelosuppression. No significant difference was observed in the incidence of ADRs for patients >= 65 versus <65 years old. Conclusions: Eribulin demonstrated effectiveness and a manageable safety profile for patients with STS, although the effectiveness of eribulin was not demonstrated for some non-L-type subtypes.