Epidemiology of mammary tumours in bitches under veterinary care in the UK in 2016

Abstract

BackgroundThere is limited information on the epidemiology of canine mammary tumours. This study aimed to estimate the incidence and risk factors for mammary tumours in UK bitches.MethodsA nested case–control study was conducted within VetCompass to estimate the frequency and risk factors for clinically diagnosed mammary tumours during 2016 (VetCompass study). A second case–control study explored further breed associations for cases confirmed histopathologically compared to the VetCompass controls (laboratory study). Multivariable logistic regression was used to evaluate associations between risk factors and mammary tumours.ResultsThe incidence of mammary tumours was 1340.7/100,000 per year (95% confidence interval: 1198.1–1483.3). A total of 222 clinical cases (VetCompass study) and 915 laboratory cases (laboratory study) were compared to 1515 VetCompass controls in the two analyses. In the VetCompass study, Springer and Cocker Spaniels, Boxers, Staffordshire Bull Terriers and Lhasa Apsos had increased odds of developing mammary tumours. Neutering was associated with reduced odds, while odds increased with increasing age and a history of pseudopregnancy. In the laboratory study, increasing age was associated with greater odds of mammary tumours, and the breeds most at risk were similar to those identified in the VetCompass study.LimitationsThe timing of neutering was not consistently available. Comparing laboratory cases to VetCompass controls provided only exploratory evidence for the breed associations identified.ConclusionsThe study provides an update on the frequency of canine mammary tumours.

Canine Mammary Tumors: Classification, Biomarkers, Traditional and Personalized Therapies

“…In 2005–2013, analysis of CMTs in the Venice and Vicenza provinces showed a standardized incidence rate of 250/100,000 dogs/year. Recently, Varney et al (2023) reported the frequency of CMTs in bitches as 1340.7 per 100,000 dogs in 2016 in the UK [ 3 ]. A study by Zheng et al (2022) showed that the relative incidence of CMTs in Mainland China between 2017–2021 was 46.71%, with a similar number of malignant and benign forms [ 4 ].…”

WSAVAguidelines for the control of reproduction in dogs and cats

“…The development of mammary tumours is complex and multifactorial. Age is one of the most relevant factors as the incidence of mam- (Donnay et al, 1994;Egenvall et al, 2005;Richards et al, 2001;Salas et al, 2015;Taylor et al, 1976;Varney et al, 2023;Zatloukal et al, 2005). Furthermore, breed (springer spaniel, cocker spaniel, boxer, poodle, dachshund; large breeds >small breeds), obesity at 1 year of age, hormone treatment and repeated pseudopregnancies (Dobson, 2013;Donnay et al, 1994;Egenvall et al, 2005;Gupta, 2012;Jitpean et al, 2012;Oliveira et al, 2022;Pastor et al, 2018;Pérez Alenza et al, 1998;Sonnenschein et al, 1991;Varney et al, 2023) and even alterations in gene expression by epigenetic mechanisms are reported predisposing factors (Borges, 2022).…”

“…Age is one of the most relevant factors as the incidence of mam- (Donnay et al, 1994;Egenvall et al, 2005;Richards et al, 2001;Salas et al, 2015;Taylor et al, 1976;Varney et al, 2023;Zatloukal et al, 2005). Furthermore, breed (springer spaniel, cocker spaniel, boxer, poodle, dachshund; large breeds >small breeds), obesity at 1 year of age, hormone treatment and repeated pseudopregnancies (Dobson, 2013;Donnay et al, 1994;Egenvall et al, 2005;Gupta, 2012;Jitpean et al, 2012;Oliveira et al, 2022;Pastor et al, 2018;Pérez Alenza et al, 1998;Sonnenschein et al, 1991;Varney et al, 2023) and even alterations in gene expression by epigenetic mechanisms are reported predisposing factors (Borges, 2022). Intact female dogs were reported to have a threefold to fourfold or higher increased risk to develop a mammary tumour and more frequently have multiple tumours in comparison to gonadectomised dogs, whereas gonadectomy decreased the odds of developing mammary tumour as well as mortality rate due to mammary tumour about threefold (Beaudu-Lange et al, 2021;Gedon et al 2021b;Grüntzig et al, 2016;Misdorp, 1988;Priester, 1979;Schneider et al, 1969;Taylor et al, 1976;Varney et al, 2023).…”

“…Intact female dogs were reported to have a threefold to fourfold or higher increased risk to develop a mammary tumour and more frequently have multiple tumours in comparison to gonadectomised dogs, whereas gonadectomy decreased the odds of developing mammary tumour as well as mortality rate due to mammary tumour about threefold (Beaudu-Lange et al, 2021;Gedon et al 2021b;Grüntzig et al, 2016;Misdorp, 1988;Priester, 1979;Schneider et al, 1969;Taylor et al, 1976;Varney et al, 2023). However, failure to consider age at gonadectomy was identified as a limiting factor in a recent large-scale retrospective study (Varney et al, 2023). For a reliable calculation of incidences, denominators should obligatorily feature a population at risk and any study should be evaluated to that effect (Moulton et al, 1970).…”