Treosulfan as salvage-therapy in metastatic breast cancer – a case report

Introduction: While treatment of metastatic breast cancer (MBC) experienced significant improvement in the past decades by introduction of highly effective drugs as taxanes and anthracyclines, survival remains relatively poor with a 5-year survival rate of 21%. Nonetheless, in some patients long-term survival can be achieved by sequential endocrine and chemotherapy treatment. During long-term treatment resistance and toxicity occur, narrowing treatment choices with every subsequent line of therapy, until no further suitable and approved therapies remain.

Treosulfan is an alkylating agent approved for treatment of ovarian cancer, exerting significant antitumor activity and low toxicity. It is highly effective against human breast cancer cells in animal model, but relevant clinical data are lacking.

Methods: We report the case of a 49-year-old woman with MBC, who previously received multiple lines of endocrine therapy, antiosteoclastic therapy, local radiation and 6 lines of chemotherapy for MBC, including docetaxel, carboplatin/gemcitabine, 5-fluorouracil/vinorelbine, liposomal doxorubicin and nab-paclitaxel. Due to significant progression of pulmonary, soft tissue and lymphatic node-metastases while being under therapy with nab-paclitaxel, salvage therapy with 7 g/m² treosulfan i.v. was initiated.

Results: 9 cycles of treosulfan were administered between 08/2012 and 06/2013, leading to complete remission of pulmonary and soft tissue metastasis, while hepatic and bone metastasis remained unchanged. Treatment was well tolerated, no grade III/IV toxicity occurred. After 12 cycles of treosulfan the patient experienced progression of hepatic metastasis, while other metastasis remained unchanged.

Conclusion: This case demonstrates that treosulfan might be effective even in heavily pre-treated patients with MBC.