# Treatment of Feline Lung–Digit Syndrome with Toceranib Phosphate: Prolonged Survival and Novel Metastatic Findings

## TL;DR

A cat with a rare lung cancer that spread to its paws and other organs was treated with toceranib phosphate, leading to long survival and good quality of life, suggesting this drug could be a helpful treatment option.

## Contribution

This is the first report of toceranib phosphate use in feline pulmonary carcinoma, showing its potential as a palliative therapy.

## Key findings

- Toceranib phosphate treatment led to prolonged survival and excellent quality of life in a cat with metastatic feline pulmonary carcinoma.
- Post-mortem analysis showed c-kit expression in one metastatic lesion, indicating tumor heterogeneity and the complexity of targeted therapy.
- The cat's rapid disease progression after discontinuing toceranib suggests the drug may help delay tumor growth.

## Abstract

Feline lung–digit syndrome is a metastatic pattern in which a primary pulmonary carcinoma spreads to the digits, often leading to delayed diagnosis and poor prognosis. Currently, no standard effective treatment exists. In this case, a cat with extensive metastatic disease was treated with toceranib phosphate as palliative therapy, achieving survival well beyond the average reported for surgical intervention alone and maintaining excellent quality of life. Post-mortem analysis revealed widespread metastases and c-kit expression, a molecular target of toceranib, in one lesion, highlighting tumour heterogeneity and the complexity of targeted therapy. This is the first report of toceranib use in feline pulmonary carcinoma, suggesting its potential as a palliative option.

Feline pulmonary carcinomas are rare and often carry a poor prognosis, particularly when associated with feline lung–digit syndrome. We report a cat with primary pulmonary carcinoma and extensive metastases—including digits, pleura, mandible, scapula, spleen, skeletal muscle, and distant lymph nodes—supporting the broader “MODAL syndrome” concept. Palliative therapy with toceranib phosphate and meloxicam achieved prolonged survival and excellent quality of life, with no adverse effects despite dose escalation. Rapid progression after discontinuation suggests a role for toceranib in delaying tumour growth. Immunohistochemistry revealed c-kit expression in one metastatic lesion but not in the primary tumour or most metastases, highlighting intratumoral heterogeneity and the complexity of targeted therapy. The observed benefit likely reflects toceranib’s multi-target activity (VEGFR2, PDGFR), impacting angiogenesis and tumour progression. This case represents the first report of toceranib phosphate use in feline pulmonary carcinoma and underscores its potential as a palliative option.