Objectives Treosulfan is offered as last-line treatment in patients with end-stage ovarian cancer. This retrospective study aimed to evaluate the response rates, overall survival, and adverse events of treosulfan in this patient population.

Methods The study included patients with end-stage platinum-resistant ovarian cancer treated with treosulfan from October 2015 to October 2020 at the Department of Oncology, Lillebaelt Hospital, University Hospital of Southern Denmark, Vejle, Denmark. Patients were included for treatment if their cancer had progressed and if other treatment options were limited. Patients receiving treosulfan as first-line treatment were excluded from the study. Response rates were evaluated according to the combined criteria of CA125 and Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Kaplan–Meier survival analyses were used to illustrate progression-free and overall survival. Adverse events were graded 1–5 according to the Common Terminology Criteria for Adverse Events version 5.0.

Results Sixty-seven patients with a median age of 72 years (range 33–92) were identified. Sixty-three (94%) patients were diagnosed with serous adenocarcinoma. Fifty-seven (85%) patients were Federation of International Gynecology and Obstetrics (FIGO) stage III or IV at the time of diagnosis. The median number of treatments prior to treosulfan treatment was 3 (range 1–8). One patient had a complete response (2%), eight patients had a partial response (13%), and 22 patients (35%) had stable disease as the best response. The median duration of response (complete or partial) was 239 days (range 43–572). Median progression-free survival was 63 days (95% CI 41 to 77). The most common adverse events were anemia (83%), fatigue (83%), anorexia (62%), nausea (57%), and constipation (41%).

Conclusions Treosulfan is an alternative for the treatment of relapsed ovarian cancer when other treatment options are limited, with response rates of approximately 15%. In general, the treatment was well tolerated. Taking the mild adverse events and the response rates into account, palliative treosulfan mainly seems beneficial for patients with performance status 0–1.