SAT-455 Analysis of a Group of Prolactinomas Resistant to Treatment with Dopamine Agonists at a University Hospital in Buenos Aires, Argentina

Prolactinomas represent approximately 40-60% of all pituitary tumors. Dopamine agonists (DA) are the first-line treatment, with a 70-90% response. However, up to 10% are resistant (R) to DA. Our objectives were to describe the clinical, biochemical and imaging characteristics of a group of patients with prolactinomas R to DA; and to determine the presence of prognostic factors by performing a comparative analysis with the population of non-R prolactinomas. We analized retrospectively the medical records of patients diagnosed with prolactinoma, with follow-up (f-up) at the same hospital from 1998 to 2017. They were classified as R when prolactin (PRL) was not normalized and/or a reduction ≤ than 50% of the tumor (Tx) volumen, with a cabergoline (CBG) dose ≥2mg/week (mg/w), with, at least 6 months of treatment. Macroadenomas (MA) were defined as Tx ≥10mm and as invasive with a classification of Knosp 3 or 4 by MRI. Of 95 prolactinomas, 14 patients with R to DA were described. The mean age was 32.7 ± 15.6 years (y). We found no statistically significant differences (SSD) in terms of gender, with a higher distribution (53%) and a tendency to age (37.9 vs 26.9, p = 0.09) in the male gender (M). The mean time of f-up was 34.7 ± 28.7 months (m). Majority were MA (87%) and invasive Tx (64%). The initial manifestations were: headache (85.7%), visual field alteration (50%), menstrual cycle alterations (86%), galactorrhea (20%). The mean PRL value was 7419.4 ± 1149.7 ng/ml, being higher in the M group (11652.6 vs 1653.3, p