Single-Agent Oral Vinorelbine as First-Line Chemotherapy for Endocrine-Pretreated Breast Cancer With Bone Metastases and No Visceral Involvement: NORBREAST-228 Phase II Study

Purpose: Single-agent oral chemotherapy is widely used in patients with bone metastases without visceral involvement, especially in hormone receptor–positive metastatic breast cancer (mBC). However, this option has been poorly evaluated in clinical trials. Methods: Eligible patients had mBC with predominantly bone but not visceral metastases, were receiving bisphosphonate therapy, and had previously received endocrine therapy (any setting) but not chemotherapy for mBC. Patients received oral vinorelbine 60 mg/m² on days 1, 8, 15, and 22 every 4 weeks (escalating to 80 mg/m² from cycle 2 in the absence of grade 3/4 toxicity) until disease progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS). Secondary endpoints included clinical benefit rate (complete/partial response or ≥24 weeks’ stable disease), overall survival, and safety. Results: Seventy patients were treated for a median of 6 cycles (range 1-18). Most (73%) continued treatment until disease progression. After 43 months’ median follow-up, median PFS was 8.2 months (95% confidence interval [CI], 5.5-9.8). The clinical benefit rate was 56% (95% CI, 43%-68%). Median overall survival was 35.2 months (95% CI, 26.8-47.1). The most common grade 3/4 adverse event was neutropenia (38% of patients); febrile neutropenia was absent. The most common grade 1/2 adverse events were bone pain, fatigue, and gastrointestinal toxicities. Alopecia was infrequent. Conclusions: In patients with hormone receptor–positive mBC, bone disease, and prior endocrine therapy, first-line oral vinorelbine chemotherapy demonstrated long PFS and good tolerability. In this setting, it could be considered as an active oral alternative to intravenous chemotherapy.