Keyhole Limpet Hemocyanin-Based Multimodal Management in Two Dogs with Presumptive Urothelial Carcinoma: Long-Term Clinical and Imaging Follow-Up

Canine urothelial carcinoma (UC) is commonly managed with non-steroidal anti-inflammatory drugs (NSAIDs), alone or combined with cytotoxic chemotherapy. Evidence supporting subcutaneous keyhole limpet hemocyanin (KLH) in canine UC is lacking. We describe two client-owned dogs with presumptive lower urinary tract UC managed with NSAIDs, KLH, and selenium after cytotoxic chemotherapy was declined. Case 1 was an 11-year-7-month-old castrated male Maltese with bladder-neck/proximal-urethral thickening. A positive veterinary bladder tumor antigen test, compatible serial imaging, and low-cellularity urine cytology showing suspected urothelial hyperplasia with dysplasia supported clinical suspicion; however, BRAF and BRAF-PLUS assays were negative and histopathology was unavailable. Case 2 was an 11-year-old neutered male Poodle with a BRAF V595E-positive urethrovesical-junction lesion on imaging, without histopathologic confirmation. Both dogs received NSAIDs, Immucothel® (1 mg subcutaneously), intravenous sodium selenite (200 μg/kg), and oral selenium (100 μg/dog q24h). Serial CT and ultrasonography documented persistent localized abnormalities over prolonged follow-up, but measurements obtained by different modalities were not treated as directly comparable. Adverse events were assessed retrospectively and not prospectively graded using VCOG-CTCAE criteria. Because the diagnoses were presumptive and the interventions were concurrent and uncontrolled, the independent contribution, efficacy, and safety of KLH cannot be determined. These cases are descriptive and hypothesis-generating.