Urotoxicity and safety data of low-dose intravenous cyclophosphamide therapy for rheumatic diseases: A Single-Center retrospective cohort study

Abstract

Despite its effectiveness in rheumatic diseases, cyclophosphamide (CYC) treatment should be used with caution due to its side effects. CYC is thought to pose a risk in the development of hemorrhagic cystitis and bladder cancer. This study aims to determine the incidence of hemorrhagic cystitis and bladder cancer with intravenous low-dose CYC therapy used in the treatment of rheumatic diseases. A total of 211 adult patients with rheumatic disease treated with intravenous CYC were evaluated in this retrospective study conducted between January 2006 and May 2021. Patient data including cumulative CYC dose, treatment frequency, duration of treatment, side effects, such as hemorrhagic cystitis and bladder cancer were acquired from medical archives. The mean follow-up period was 48.5 (3–180) months, and the mean cumulative CYC dose was 5g (2–19g). None of the patients received mesna therapy concurrent with CYC therapy. 11 patients developed hemorrhagic cystitis (5.2%). Hemorrhagic cystitis was found to be statistically significantly associated with the number of CYC cycles (p=0.04). All patients were asymptomatic. No statistically significant difference was observed between hemorrhagic cystitis, treatment duration, and cumulative dose for CYC therapy in rheumatic diseases. Malignancy developed in 12 patients (5.7%) after CYC treatment. Bladder cancer was observed in 1 patient. According to our findings, the only risk factor for hemorrhagic cystitis in patients receiving CYC was the number of CYC cycles. Intravenous CYC regimen did not cause symptomatic hemorrhagic cystitis. Low-dose IV CYC may be safe in terms of serious urotoxic side effects when used at the appropriate dose, duration and frequency.