Study backs regular proteinuria monitoring during masitinib treatment

Use of weekly proteinuria monitoring in the first month of masitinib treatment for neoplasia has been supported in a study.

In the study – “Development and progression of proteinuria in dogs treated with masitinib for neoplasia: 28 cases (2010-2019)”, published in the Journal of Small Animal Practice – clinical records from dogs referred to a single university teaching hospital for neoplasia treatment with masitinib were retrospectively evaluated.

Urinalysis results were only included if they were performed at a reference laboratory. At each timepoint, the urine was classified as non-proteinuric (urine protein:creatinine ratio [UP:C] ≤0.5) or proteinuric (UP:C >0.5). Proteinuria was then categorised as likely pre-renal, post-renal, physiological renal or pathological renal.

Dogs were grouped based on the presence or absence of proteinuria at baseline. Non-proteinuric dogs were further divided, based on whether proteinuria developed following treatment during the study.

Findings

Twenty-eight dogs were included in the study – 5 dogs were being treated for epitheliotropic lymphoma, 1 for vulval lymphoma, 1 for malignant melanoma and 21 for mast cell tumours.

Twenty-two (79%) of the dogs were non-proteinuric and six were proteinuric at baseline.

Of the dogs that were non-proteinuric at baseline, four (18.2%) developed proteinuria within one month of treatment initiation. Median time to first detection of proteinuria was 14.5 days (range: 13 to 31).

Of the six dogs with pre-treatment proteinuria, masitinib treatment was discontinued in three dogs due to lack of efficacy and three were euthanised during treatment – two for disease progression and one for an unknown reason.

Investigate

Margaux Kuijlaars, corresponding author for the paper, said: “Patients developing proteinuria should be investigated to exclude non-renal causes. This should allow for more informed recommendations on the monitoring and management of proteinuria, and further masitinib treatment in these patients to be made.

“Masitinib treatment can be considered in patients with pre-treatment proteinuria and does not inevitably cause worsening of proteinuria.

“The findings of this study add to the evidence base for the use of masitinib in treating neoplasia in small animal patients. The use of masitinib in dogs in this study was off licence as [tyrosine kinase receptor] C-KIT mast cell tumour expression was not determined, and many dogs were treated for other tumours.”