The Definitive-Intent 10-Fraction Radiotherapy Protocol ('The Zurich Protocol') Yields Lasting Tumour Control and...

Area of Science:

• Veterinary Oncology
• Radiation Oncology
• Comparative Oncology

Background:

• Intracranial meningiomas are common brain tumors in dogs.
• Definitive-intent radiotherapy aims to control tumor growth and prolong survival.
• Moderately hypofractionated protocols can shorten treatment duration while managing toxicity.

Purpose of the Study:

• To evaluate oncologic outcomes and toxicity in dogs with intracranial meningiomas treated with a 10-fraction definitive-intent radiotherapy protocol.
• To identify radiation dose-volume-related prognostic factors.
• To assess the efficacy and safety of this hypofractionated approach.

Main Methods:

• Retrospective review of 110 dogs with imaging-based intracranial meningiomas treated between 2015 and 2025.
• All dogs received 10 daily fractions of 4 Gy radiotherapy.
• Treatment plans included homogeneous dose, risk-adapted heterogeneous dose distributions, or a simultaneously integrated boost (SIB).

Main Results:

• Median time to progression was 873 days; median overall survival was 756 days.
• Larger volumes of normal brain receiving ≥32 Gy were associated with shorter survival.
• Simultaneously integrated boost (SIB) use correlated with shorter disease-specific survival; post-radiotherapy seizures reduced time to progression.

Conclusions:

• The 10-fraction definitive-intent radiotherapy protocol provides durable tumor control and survival for canine intracranial meningiomas.
• Respecting brain dose-volume constraints is essential for favorable outcomes.
• Toxicity was generally mild, transient, and responsive to corticosteroids.