Prophylactic strategies to reduce cyclophosphamide-induced sterile hemorrhagic cystitis in dogs: a first-opinion practice retrospective study and a referral survey
Arturs Ivanovs, Christina MacKenzie, Zoe Wardle, Gina Pinchbeck, Heather Grieve, Peter-John Noble, David Roper KillickAbstract
Background
Cyclophosphamide occasionally causes sterile hemorrhagic cystitis (SHC) in dogs. Prophylactic coadministration of furosemide reduces SHC risk, yet the extent of the implementation in practice is unknown.
Hypothesis/Objectives
To explore the frequency of cyclophosphamide and furosemide coadministration in first opinion practice (FOP) and referral settings.
Animals
Small Animal Surveillance Network (SAVSNET) searches identified 106 dogs receiving cyclophosphamide, of which 72 met the inclusion criteria.
Methods
This study was composed of: (1) electronic health record (EHR) review using the SAVSNET database, in which data regarding dosage, co-prescribed medications, preventative measures, and suspected SHC occurrence were collated (2014-2024); and (2) a survey of referral oncology practitioners and educators (2023-2024) exploring contemporary approaches to SHC prevention.
Results
Treatment approaches were evenly divided between maximum-tolerated dose cyclophosphamide (MTDC, 53%) and metronomic cyclophosphamide (MC, 47%). Furosemide was prescribed in 32% of cases, most commonly with MTDC protocols (53%). The overall frequency of suspected SHC was 15% (11/72); notably, no suspected SHC cases occurred in dogs receiving furosemide (P = .013). Survey results showed frequent use of prophylactic diuretics: 88% recommended furosemide for MTDC and 55% for MC protocols.
Conclusions and clinical importance
Diuretic co-prescription with cyclophosphamide was inconsistent in FOP, which was unexpected given the prior evidence regarding reduction of risk of SHC. Greater standardization of guidance and improved dissemination of best-practice recommendations are necessary to optimize dog safety.