Survival, neurologic response, and prognostic factors in dogs with pituitary masses treated with radiation therapy and untreated dogs

Background: Pituitary masses in dogs are not uncommon tumors that can cause endocrine and neurologic signs and, if left untreated, can decrease life expectancy. Hypothesis: Dogs with pituitary masses that received radiation therapy (RT) have more favorable neurologic outcomes and longer survival times compared with untreated dogs. Animals: Nineteen dogs with a pituitary mass identified on CT or MR imaging were irradiated with 48 Gy given in 3 Gy daily-dose fractions. Twenty-seven untreated control dogs had pituitary masses. Methods: Medical records of dogs with pituitary masses were retrospectively reviewed for clinical signs, mass size, and outcome. Results: Median survival time was not reached in the treated group. Mean survival time in the treated group was 1,405 days (95% confidence interval [CI], 1,053-1,757 days) with 1-, 2-, and 3-year estimated survival of 93, 87, and 55%, respectively. Median survival in the nonirradiated group was 359 days (95% CI, 48-916 days), with a mean of 551 days (95% CI, 271-829 days). The 1-, 2-, and 3-year estimated survival was 45, 32, and 25%, respectively. Dogs that received RT for their pituitary tumors had significantly longer survival times than untreated dogs (P = .0039). Treated dogs with smaller tumors (based on maximal pituitary-to-brain height ratio or area of tumor to area of brain) lived longer than those with larger tumors (P < .001). Conclusions and Clinical Importance: When compared with untreated dogs, RT increased survival and controlled neurologic signs in dogs with pituitary masses.