Life course analysis of the impact of mammary cancer and pyometra on age-anchored life expectancy in female Rottweilers: Implications for envisioning ovary conservation as a strategy to promote healthy longevity in pet dogs.

Mammary cancer and pyometra are important health hazards associated with ovary conservation in pet dogs. Early ovariohysterectomy may reduce the incidence of these two diseases, but an estimate of the extent to which the development of mammary cancer or pyometra adversely influences overall longevity is missing. As a first step toward addressing this knowledge gap, the results of a historical cohort study of Rottweilers that lived in North America are reported. Questionnaires completed by owners and veterinarians were used to obtain lifetime health and medical information on 242 female Rottweilers, including years of lifetime ovary exposure, age at death, and cause of death. To determine the extent to which longevity was shortened in females that developed these ovary-associated diseases, age-anchored life expectancy-defined as the median number of remaining years until death for females alive at specified ages during the life course-and years of life lost, a measure of premature mortality, were estimated. Mammary carcinoma was diagnosed in 19 (7.9%) females; median age at diagnosis was 8.5 years; case fatality was 37%. Pyometra was diagnosed in 16 (6.6%) females; median age at diagnosis was 5.4 years; case fatality was 7%. Median lifetime ovary exposure for the study population was 4.3 years. Although risk for developing both diseases increased with longer ovary exposure, longer ovary exposure (≥4.3 years) was also associated with an overall longevity advantage-a 33% decrease in mortality, living 17 months longer than females with shorter ovary exposure (P=0.002). Analysis of age-anchored life expectancy showed that at no time points during the life course was the current or future diagnosis of mammary carcinoma or pyometra associated with shortened survival compared to females who never developed these conditions. This lack of longevity disadvantage is an expected result for diseases with late-onset, moderate (<50%) case fatality (mammary carcinoma) or low (<10%) case fatality (pyometra). These findings fail to support the notion that a strategy, such as elective ovariohysterectomy, implemented to reduce the incidence of mammary carcinoma and pyometra will beneficially impact overall longevity. It follows that future efforts to find and implement effective longevity-promoting interventions should look beyond reducing the incidence of a particular disease to considering trade-offs.