Spaying bitches at time of mastectomy

It is advisable to always spay a bitch having a mastectomy.

Approximately 50% of malignant mammary tumours in the dog have receptors for either oestrogen or progesterone. This means the presence of these female hormones promotes the growth of these tumours.

Benign tumours also have female hormone receptors and can also be stimulated by hormonal cycling of the female dog. This means spaying is important, even if a tumour has already developed.

In one study, bitches spayed at the time of mammary tumour removal (or two years prior) lived 45% longer than those that remained unspayed.