Canine and feline mammary carcinomas exhibit a wide range of clinical behaviors, depending on numerous histologic and clinical factors.1-7 Veterinary oncologists typically use median survival time after cancer is diagnosed to predict survival rates. Conditional survival, frequently used in human oncology, is the probability of continued survival (measured in months) based on how many months the patient has already survived since the time of diagnosis. This can be further refined based on whether certain criteria are met.
This study sought to describe the one-year overall and cancer-specific conditional survival of female dogs and cats with invasive mammary carcinomas. A secondary goal was to analyze the influence of epidemiologic, clinical, histopathologic, and immunohistochemical parameters on conditional survival.
Records of 344 dogs and 342 cats were retrospectively reviewed for patients with invasive mammary carcinomas treated with surgery alone and with a 2-year follow-up. Dogs that lived at least one year after diagnosis were relatively protected against cancer-related death. The one-year conditional specific survival probability increased from 59% to 80% in this population of dogs. Factors associated with conditional survival in dogs included patient age, nodal stage, cancer stage, lymphovascular invasion, proliferation index, and margin status.
Feline mammary carcinoma remains a life-threatening condition, even when survival is one year after diagnosis; one-year conditional specific survival probability increased from 48% to 52% in cats.
Conditional survival has been used for a variety of tumors in human medicine, including breast and pancreatic cancer, but has not been investigated in veterinary oncology. Conditional survival is potentially useful for more accurately estimating patient outcomes, especially when identifying prognostic factors in those patients surviving the period in which they are most likely to succumb to disease.
