27Background: Pituitary carcinoma (PC) is an aggressive neuroendocrine tumor diagnosed when a pituitary 28 adenoma (PA) becomes metastatic. PCs are typically resistant to therapy and frequently recur. Recently, 29 treatment with temozolomide (TMZ) has shown promising results, although the lack of prospective trials 30 limits accurate assessment. Methods: We describe a single-center experience in managing PC over a [22][23][24][25][26][27][28][29][30][31] year period and review previously published PC series. Results: 17 patients were identified. Median age 32 at PC diagnosis was 44 years (range 16-82), and the median PA-to-PC conversion time was 5 years (range 33 1-29). Median follow-up was 28 months (range 8-158) with 7 deaths. Most PC were hormone-positive 34 based on immunohistochemistry (n=12): ACTH (n=5), PRL (n=4), LH/FSH (n=2), GH (n=1). All patients 35 underwent at least one resection and one course of radiation after PC diagnosis. Immunohistochemistry 36 showed high Ki-67 labeling index (>3%) in 10/15 cases. Eight patients (47%) had metastases only to the 37 CNS, and 6 (35%) had combined CNS and systemic metastases. The most commonly used chemotherapy 38 was TMZ, and TMZ-based therapy was associated with the longest period of disease control in 12 (71%) 39 cases, as well as the longest period from PC diagnosis to first progression in 8 (47%) cases. The 2, 3 and 40 5-year survival rate of the entire cohort was 71%, 59% and 35%, respectively. All patients surviving >5 41 years were treated with TMZ-based therapy. Conclusions: PC treatment requires a multidisciplinary 42 3 approach and multimodality therapy including surgery, radiation and chemotherapy. TMZ-based therapy 43 was associated with higher survival rates and longer disease control. 44 45 Precis 46 We describe 17 PC patients who were diagnosed and treated at MDACC over a 22-year period. 47