Breast Cancer Research and Treatment13:4%60 (1989) © KluwerAcademic Publishers- Printedin the Netherlands Report Histopathologic and dietary prognostic factors for canine mammary carcinoma Frances S. Shofer, Elizabeth G. Sonnenschein, Michael H. Goldschmidt, Larry L. Laster and Lawrence T. Glickman University of Pennsylvania School of Veterinary Medicine, Philadelphia, PA, USA Key words: breast neoplasms, canine, mammary tumors, dietary fat, dietary protein, histopathology, prognosis Summary Histologic and dietary prognostic factors for survival following naturally occurring breast cancer were studied for 145 pet dogs. Information was collected from the dog's owner and veterinarian regarding medical and reproductive history, nutritional status, treatment, tumor recurrence, and length of survival. The usual intake of all dog and table foods consumed 1 year prior to diagnosis was obtained using a validated quantitative food frequency questionnaire. A histologic malignancy score was derived based on 7 histopath- ologic criteria. The mean age of the dogs was 10.4 + 2.5 years; 37% had been ovariohysterectomized prior to diagnosis. Product-limit estimates of survival indicated that 6 factors, namely body conformation i year prior to diagnosis (p = 0.03), histologic tumor type (p = 0.004), histologic malignancy score (p = 0.02), histologic invasion (p = 0.002), tumor recurrence (p<0.0001), and completeness of surgery (p = 0.01) were of prognostic significance. In addition, when dogs were characterized by the percent of total calories they derived from fat and protein, the median survival time for dogs in the low fat group (<39%) with protein >27%, 23-27%, and <23% was 3 years, 1.2 years, and 6 months, respectively (p = 0.008). For dogs in the high fat group (-39%), there was no difference in survival for the different intake levels of dietary protein (p = 0.84). When these data were fitted to a proportional hazards model, recurrence, histologic score, tumor type, percent of calories derived from protein, fat group, and a protein-fat group interaction term were statistically significant. Predicted 1 year survival for dogs on a low fat diet with 15%, 25%, and 35% of total calories derived from protein was 17%, 69%, and 93%, respectively. Introduction Ecologic studies have shown that per capita con- sumption of dietary fat is positively correlated with mortality rates of breast cancer in women [1-2]. In addition, higher survival rates for breast cancer patients are found in countries with characteristi- cally low breast cancer rates [34]. For example, Japanese women compared with American women had significantly longer survival times for breast cancer [5-7], particularly if they were postmeno- pausal; the 10-year survival rates for postmenopau- sal women were 31% and 60% for American and Japanese women, respectively. Cohort studies have generally failed to clarify the role of dietary fat in the prognosis and survival of patients with breast cancer due to weaknesses in study design [8-9]. With regard to obesity or large body mass, Addressfor offprints: F. S. Shofer, Sectionof Epidemiology, Departmentof ClinicalStudies,University of Pennsylvania Schoolof VeterinaryMedicine,3850Spruce Street, Philadelphia, PA 19104,USA
