What is the effect of spaying on mammary tumours in dogs?


Dog mammary cancerIt has been commonly quoted that neutering bitches reduces the risk of mammary tumours. However, an interesting systematic review carried out by the Veterinary Epidemiology and Public Health Group, Royal Veterinary College (RVC), found that the evidence for this understanding was weak.

Beauvais, W, Cardwell, J. M. and Brodbelt*, D. C. (2012) The effect of neutering on the risk of mammary tumours in dogs - a systematic review. Journal of Small Animal Practice, 53(6), pp 314-322 (electronic access available to Library members)

*D.C. Brodbelt is a member on the Science Panel of the 1st International Evidence-Based Veterinary Medicine Network Conference



Other references of interest

  • Smith, A. (2014) The role of neutering in cancer development. Veterinary Clinics of North America: Small Animal Practice, 44 (5), pp. 965-975
  • Zink, M.C. et al. (2014) Evaluation of the risk and age of onset of cancer and behavioral disorders in gonadectomized Vizslas. Journal of the American Veterinary Medical Association, 244 (3), pp 309-319
  • Kristiansen, V. M. et al. (2013) Effect of ovariohysterectomy at the time of tumor removal in dogs with benign mammary tumors and hyperplastic lesions: a randomized controlled clinical trial. Journal of Veterinary Internal Medicine, 24(4), pp. 935-942 (electronic access available to Library members)
  • Root Kustritz, M. V. (2007) Determining the optimal age for gonadectomy of dogs and cats. Journal of the American Veterinary Medical Association, 231 (11), pp 1665-1675 (electronic access available to Library members)
  • Bars, C. F. le (2006) Benefits, risks and myths: is early neutering best option for bitches? Veterinary Times, 36(24), pp. 16-17


A few more selected references from our search on CAB Abstracts database are available to download from our 'Related documents' box


Search strategy

The following search terms were used:

1     (spay* or neuter* or spey* or ovari*tom* or gonadect*)

2     (mammar* or breast)

3     (tumor* or tumour* or cancer* or neoplas*)

4     (dog or dogs or bitch* or canine)

5     (1 and 2 and 3 and 4)


A broader search strategy would be to combine the search terms as:


5     (1 and 2) or (2 and 3 and 4)


If you would like to learn more about searching databases, and constructing search strategies, we would be happy to arrange a one-to-one session at a time to suit you. Email us at library@rcvsknowledge.org



Photo: 9-months-old mammary tumor in a bitch, author, L. Mahin. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license