Systematic Review: Does Pre-Pubertal Spaying Reduce the Risk of Canine Mammary Tumours?

Area of Science:

• Veterinary Medicine
• Canine Health
• Surgical Procedures

Background:

• Ovariectomy and ovariohysterectomy (spaying) are common surgical procedures in dogs.
• The optimal age for spaying remains debated, with historical recommendations for pre-pubertal spaying based on perceived mammary cancer risk reduction.
• Recent evidence has questioned the established link between early spaying and reduced mammary tumor development.

Purpose of the Study:

• To systematically review updated literature on the relationship between the age of spaying in dogs and mammary tumor development.
• To assess whether the evidence regarding early spaying and mammary tumor risk has changed since previous reviews.

Main Methods:

• A systematic review adhering to PRISMA guidelines was performed.
• Peer-reviewed articles were searched in March 2023 across CAB direct, Web of Science, and PubMed databases.
• Exclusion criteria included non-English articles, non-peer-reviewed studies, irrelevant PICO, or studies focusing on existing tumors or prognosis rather than development.

Main Results:

• Out of 232 initial articles, 13 met the inclusion criteria.
• A significant finding was that six of the thirteen selected studies found no evidence supporting a protective effect of early spaying against mammary tumor development.

Conclusions:

• The current literature suggests that the protective effect of early spaying against mammary tumors is not consistently supported.
• Further breed-specific studies with matched controls are recommended to address biases and confounding factors.
• The benefits of early spaying should be carefully weighed against other factors when determining the optimal age for spaying dogs.