Back to home page

Age at neutering and mammary tumours in bitches

Clinical Scenario

Tess is an an 8 month old Border collie entire bitch whose owner would like her to be spayed. The owner’s previous Border collie was euthanased after developing mammary neoplasias which metastasised to axillary LNs. They want to know whether spaying Tess before her first season will offer a reduced risk of mammary neoplasia as compared to waiting until after her first season...

3-Part Question (PICO)

In [bitches being spayed] does [surgery before first season compared to later] reduce [risk of mammary tumours]?

Search Strategy and Summary of Evidence

Search Strategy

MEDLINE(R) In-Process & Other Non-Indexed Citations and MEDLINE(R) 1946 to Present using the OVID interface

(dog.mp. OR dogs.mp. OR canine.mp. OR canines.mp. OR canis.mp. OR bitch.mp. OR bitches.mp. OR exp Dogs/)

AND

(neuter.mp. OR neuters.mp. OR neutering.mp. OR sterilise.mp. OR sterilize.mp. OR sterilisation$.mp. OR sterilization$.mp. OR spay$.mp. OR spey$.mp. OR de sex$.mp. OR desex$.mp. OR gonadectomy.mp. OR gonadectomise.mp. OR hysterectomy.mp. OR hysterectomies.mp. OR ovariectomy.mp. OR ovariectomies.mp. OR ovariohysterectomy.mp. OR ovariohysterectomies.mp. OR exp Ovariectomy/ OR exp Hysterectomy/ OR exp Sterilization, Reproductive/)

AND

(mammary tumour.mp. OR mammary tumours.mp. OR mammary tumor.mp. OR mammary tumors.mp. OR mammary adenoma$.mp. OR mammary adenocarcinoma$.mp. OR mammary carcinoma$.mp. OR mammary neoplasia$.mp. OR mammary neoplasm$.mp. OR mammary gland neoplasm$.mp. OR exp Mammary Neoplasms, Animal/)

CAB Abstracts 1910 to Present using the OVID interface

(dog.mp. OR dogs.mp. OR canine.mp. OR canines.mp. OR canis.mp. OR bitch.mp. OR bitches.mp. OR exp dogs/ OR exp bitches/)

AND

(neuter.mp. OR neuters.mp. OR neutering.mp. OR sterilise.mp. OR sterilize.mp. OR sterilisation$.mp. OR sterilization$.mp. OR spay$.mp. OR spey$.mp. OR de sex$.mp. OR desex$.mp. OR gonadectomy.mp. OR gonadectomise.mp. OR hysterectomy.mp. OR hysterectomies.mp. OR ovariectomy.mp. OR ovariectomies.mp. OR ovariohysterectomy.mp. OR ovariohysterectomies.mp. OR exp sterilization/ OR exp gonadectomy/ OR exp hysterectomy/ OR exp ovariectomy/)

AND

(mammary tumour.mp. OR mammary tumours.mp. OR mammary tumor.mp. OR mammary tumors.mp. OR mammary adenoma$.mp. OR mammary adenocarcinoma$.mp. OR mammary carcinoma$.mp. OR mammary neoplasia$.mp. OR mammary neoplasm$.mp. OR mammary gland neoplasm$.mp. OR exp mammary gland neoplasms/)

Search Outcome

MEDLINE

  • 65 papers found in MEDLINE search
  • 62 papers excluded as they don't meet the PICO question
  • 0 papers excluded as they are in a foreign language
  • 2 papers excluded as they are review articles/in vitro research/conference proceedings
  • 1 total relevant papers from MEDLINE

CAB Abstracts

  • 155 papers found in CAB search
  • 141 papers excluded as they don't meet the PICO question
  • 0 papers excluded as they are in a foreign language
  • 12 papers excluded as they are review articles/in vitro research/conference proceedings
  • 2 total relevant papers from CAB

Total relevant papers

2 relevant papers from both MEDLINE and CAB Abstracts

Comments

There is only one paper included in the summary of evidence, as the study by Schneider et al. is included in the Beauvais et al. systematic review.

Summary of Evidence

Beauvais et al. (2012) UK

Title:

The effect of neutering on the risk of mammary tumours in dogs—a systematic review.

Patient group:

Peer-reviewed English language articles identified by searches in CAB Direct, NLM (PubMed) and Web of Knowledge to assess associations between neutering or age of neutering and the risk of mammary neoplasia in the bitch

Study Type:

Systematic review

Outcomes:
  • The effect of age at neutering on the frequency of mammary tumours in bitches
  • The effect of neutering on the frequency of mammary tumours in bitches

Key Results:
  • 11147 records identified
  • Filtered to 13 relevant papers
  • 9 were excluded as at high risk of bias
  • The remaining studies had a moderate risk of bias. These 4 studies were included and assessed. Only 1 of these studies addressed this BET question specifically (Schneider et al, 1969)
  • All of the studies identified had at least a moderate risk of bias, as assessed using the SIGN system
  • There was limited evidence to suggest that spaying bitches before the first season, second season and before 2.5 years of age was associated with a reduction in the risk of development of malignant mammary neoplasia
  • This reduction in risk appeared to be greatest in the bitches spayed before their first season, followed by those spayed before their second season
  • Evidence was assessed by the authors as category ‘D’ according to SIGN (weakest category of evidence)
Study Weaknesses:
  • Only studies published in a peer reviewed section of a journal included and no grey literature searched*
  • Only English language papers included*
  • No attempts to track down missing data


*However, the authors comment that they feel that these exclusions were not detrimental and could actually have reduced the quality of the study if included

Attachment:
No attachments.

Comments

This was a clear and well written systematic review which suffered from a lack of good quality evidence on this topic. Only one paper in the systematic review addressed the specific question of age at neutering and risk of mammary tumours (Schneider et al.). It is worth noting that the population of dogs included in that study had all had pathology samples submitted for mammary neoplasms, and the comparison made was between benign and malignant neoplasia.

Bottom line

Spaying bitches before the first or second season, or before the age of 2.5 years, may be associated with a reduced risk of developing malignant mammary tumours later in life. This reduction in risk appears to be most marked in the bitches spayed before their first season, followed by those spayed before their second season. However, the evidence is relatively weak, and this should be taken into account alongside other considerations when recommending whether and when to neuter.

Disclaimer

The BETs on this website are a summary of the evidence found on a topic and are not clinical guidelines. It is the responsibility of the individual veterinary surgeon to ensure appropriate decisions are made based on the specific circumstances of patients under their care, taking into account other factors such as local licensing regulations. Read small print

References

Beauvais W, Cardwell JM, Brodbelt DC (2012) The effect of neutering on the risk of mammary tumours in dogs—a systematic review. Journal of Small Animal Practice 53: 314-322.

Schneider R, Dorn CR, Taylor DO (1969). Factors influencing canine mammary cancer development and postsurgical survival. Journal of the National Cancer Institute 43: 1249-1261.

About this BET

First author:
Jenny Stavisky
Second author:
Kathryn Wareham
Institution:

CEVM, University of Nottingham

Search last performed:
2018-05-10 15:53:15
Original publication date:
2013-09-13 15:53:15
Last updated:
2018-05-10 15:53:15
About BETs?

A BET is a simple method of searching for and appraising evidence around a very specific clinical situation.

Read more …

Using BETs?

BETs don’t tell you what to do, they tell you about the evidence on a certain topic.

Read more …

Not a Vet?

This website has been designed to help vets use the best, most relevant, up to date science when they make decisions about their patients.

Read more …