A retrospective study and survival analysis on bitches with mammary tumours spayed at the same time of mastectomy

Abstract

The aim of the present study was to retrospectively assess whether spaying at the same time of mastectomy increased disease-free survival (DFS) in bitches with mammary tumors and to investigate the utility of clinical data when designing a surgical plan that includes gonadectomy. Data from 225 bitches were retrieved. Only 116 were surgically treated. Among these, 52 bitches underwent mastectomy and ovariectomy and 46 bitches underwent mastectomy alone. Survival analysis by Kaplan-Meier and in-between groups comparisons using Student's T, Chi-square, and one-way ANOVA tests were performed. Eighteen bitches were already spayed. DFS was longer for bitches that underwent ovariectomy and mastectomy compared to those that were left intact (P=0.00064) or were already spayed (P=0.0098). Spaying status affected the tumor size (spayed: 2.75 cm±2.72; intact: 1.76 cm±2.04; P=0.039), but not malignancy (P>0.05). Differences in age were detected between animals with benign and malignant tumors (9.1±2.8 and 10±2.3; P=0.004), with multiple and single tumors (10.18±2.6 and 9.3±2.8; P=0.007), and between purebred and mixed breed bitches (10.46 years ±1.78 and 9.27 years ±2.68; P = 0.005). Malignant tumors were larger than benign ones (2.17 years ±2.31 and 1.34 years ±1.82; P = 0.005) and size increased according to the degree of malignancy. DFS was shorter for animals presenting tumors >2 cm in size (P<0.006) and with tumors in the first pair of thoracic mammary glands (P=0.00009).Gonadectomy should be suggested to owners of intact bitches carrying mammary tumors and age, size of the tumor, and location should be carefully considered when performing surgery.

Risk factor analysis and clinicopathological characteristics of female dogs with mammary tumours from a single-center retrospective study in Poland

“…In this study, smaller median tumour size was noted in intact dogs compared with spayed dogs, which was in agreement with a previous study 58 . In addition, benign tumours and non-neoplastic lesions were smaller compared with malignant tumours 58 , 59 .…”

“…In this study, smaller median tumour size was noted in intact dogs compared with spayed dogs, which was in agreement with a previous study 58 . In addition, benign tumours and non-neoplastic lesions were smaller compared with malignant tumours 58 , 59 . More recently, other authors noticed that the risk of having a malignant tumour increased approximately 1.5-fold with each 1.0 cm of increase in tumour size, while the risk increased approximately 11.8-fold when the tumour was larger than 5.0 cm compared with smaller tumours (< 3 cm) 60 .…”

“…We found no association between the quantity of masses and the age of the dog. Although some studies have stated that multiple tumours were more frequent in old dogs, the mean age difference between dogs with multiple and single tumours was not large (10.1 years vs. 9.3 years, respectively) 54 , 58 .…”

“…Some studies have shown a nearly equal incidence (45.6% single vs. 54.4% multiple) 59 . Multiple tumours were more common in hormonally active dogs, suggesting the effect of hormonal exposure on tumour multiplicity, potentially decreased by OH 54 , 58 , 59 , 72 , 77 , but one other report found no association 78 . On the other hand, the percentage of multiple tumours was significantly lower compared with single CMTs among intact bitches.…”

Associations Between Dog Breed and Clinical Features of Mammary Epithelial Neoplasia in Bitches: an Epidemiological Study of Submissions to a Single Diagnostic Pathology Centre Between 2008–2021

“…A recent systematic review questioned the strength of the epidemiological evidence supporting an association between neutering and mammary tumour risk in dogs, in particular relating to the timing of neutering [ 12 ], however, the data are overall consistent that neutering (particularly at a younger age) reduces mammary tumour risk [ 13 ]. If an entire animal develops a mammary tumour, neutering combined with mastectomy significantly increases survival compared to neutering alone [ 14 ] although estrogen may have a protective effect in animals with estrogen receptor (ER) negative tumours [ 15 ], so neutering may be counterproductive in these cases. Like human breast cancer, canine mammary tumours which lack hormone receptors tend to be more aggressive [ 16 – 18 ].…”