A retrospective analysis on the outcome of 18 dogs with malignant ovarian tumours

Little evidence is available regarding the prognosis of dogs with malignant ovarian tumours. The objective of this retrospective study was to describe the outcomes and determine the prognostic factors for dogs with malignant ovarian tumours following treatment, including surgery with or without adjuvant therapy. Eighteen dogs were studied, their median age was 12 years (range: 7-15 years), and their median body weight was 6.9 kg (range: 2.3-17.8 kg). Following histopathologic diagnoses revealed that granulosa cell tumour was the most common type (n = 9), followed by dysgerminoma (n = 5), and adenocarcinoma (n = 4). Eleven dogs had surgery alone. Seven dogs had surgery with adjuvant therapy, including chemotherapy and/or radiotherapy. The median survival time (ST) was 1009 days when only deaths owing to the ovarian tumours were considered, and predictors of median ST were T-category (≥ T3, 443 days vs ≤ T2, 1474 days; P = .002), presence of metastatic disease (present, 391 days vs absent, 1474 days; P < .001) and lymphovascular space invasion (present, 428 days vs absent, 1474 days; P = .003) in a univariate analysis. Median ST in dogs with granulosa cell tumour seemed longer than in dogs with dysgerminoma and adenocarcinoma, although the difference was statistically insignificant (1474 days vs 458 days, respectively; P = .10). Considering the good prognosis, aggressive treatment can be recommended for dogs with malignant ovarian tumours, especially early-stage cases. Despite metastasis being present at diagnosis, half of the dogs with metastasis survived for more than 1 year.