Postoperative treatment outcome in canine mammary tumors. Multivariate analysis of the prognostic value of pre- and postoperatively available information.

Abstract

OBJECTIVE: Mammary tumors belong to the most common canine neoplasias. Few data are available on postoperative outcome and independent prognostic value of variables including pre-operatively available parameters such as cytology. The aim of this study was to characterize outcome following surgery and identify independent prognostic factors in canine mammary tumors. MATERIAL AND METHODS: Prospective study in which dogs with mammary tumors underwent surgical tumor removal followed by histopathologic examination of the neoplasias. Kaplan-Meier log rank analysis and multivariate regression analyses were used to evaluate survival, recurrence-free interval (RFI) and metastasis free interval (MFI) as well as independent influence of variables on outcome. RESULTS: 134 dogs with mammary tumors were included. In 126 dogs without distant metastasis, overall survival duration was 1113 d; median RFI and MFI were not reached. Histologic grade showed independent influence on duration of RFI (p=0.040), MFI (p=0.007), and survival (p=0.029). Median survival in benign (n=98), grade 1 (n=10) and grade 2 (n=16) malignant tumors was 1319 d, 670 d, 406 d, respectively. Cytology exerted independent influence on the likelihood for recurrence (p=0.013), duration of RFI (p=0.026) and survival (p=0.030). CONCLUSION AND CLINICAL RELEVANCE: Histologic grade was of independent prognostic significance for postoperative outcome in this population of dogs with mammary tumors. As a pre-operatively available parameter, cytology may also possess prognostic value in canine mammary neoplasias.