Should we recommend spaying cats for mammary tumour prevention, and if so, at what age?

TL;DR

Spaying female cats may reduce their risk of mammary tumors, especially if done before one year of age, but more research is needed to confirm this.

Contribution

The study evaluates the effectiveness of spaying in reducing mammary tumors in cats and suggests an optimal spaying age.

Findings

Spaying female cats reduces the risk of mammary tumors.

Spaying before one year of age provides a protective effect, while spaying after two years may increase risk.

Current evidence has moderate to high risk of bias and requires further clinical trials.

Abstract

In cats does spaying versus non-spaying reduce the risk of mammary tumours?

Risk.

Four studies were reviewed: three case-control studies and one retrospective cohort study.

Weak.

All four studies found a protective effect of spaying female cats against mammary tumour. One study assessed the age of spaying and found a protective effect only when spaying was performed before 1 year of age, whereas spaying after 2 years of age was associated with an increased risk of developing mammary tumour compared to intact cats. These publications contain a moderate to high risk of bias.

Based on the available evidence, spaying appears to reduce the risk of mammary tumours development in female cats. The data suggest that the protective effect is more pronounced when spaying is performed at an earlier age. However, due to the weak nature of the current evidence, further well-designed clinical trials are needed to confirm these findings and determine the optimal age for spaying.