Endocrine Abstracts

JOINT675

Introduction: Invasive macroprolactinomas respond less favorably to dopamine agonist (DA) therapy compared to non-invasive macroadenomas and microadenomas. Understanding the frequency of a good response (GR) —defined as prolactin (PRL) normalization and ≥50% tumor volume reduction—and its predictors may aid timely clinical decision-making. Therefore, the current study focused on assessing GR frequency at the first-year follow-up and determining predictive factors of this response in patients with invasive macro-giant prolactinomas.

Methods: This retrospective cohort study included 38 patients (32 males, 6 females; mean age 41.9±12.8 years) with invasive macro-giant prolactinomas (baseline median PRL: 2530 (1726–5451) ng/mL, mean longest tumor diameter: 36.4±12.8 mm) who were followed for at least one year under cabergoline therapy. PRL levels and tumor volume changes were analyzed at early and late follow-ups. Patients were classified as good responders (GRs) or poor responders (PRs) based on their first-year outcomes.

Results: At the first-year visit, 17 patients (44.7%) achieved a GR. Baseline parameters such as presenting symptoms and signs, hormonal studies, tumor invasion characteristics, and KNOSP scores were comparable between groups, but GRs had significantly higher normoprolactinemia rates (70.6% vs. 23.8%,P = 0.004) and greater tumor shrinkage (57.3±15.6% vs. 41.9±21.9%,P = 0.02) at 3–6 months evaluations. In the multivariate logistic regression analysis, the best-reduced model to predict GR in the first year included tumor shrinkage percentages (aOR:1.06 (95% CI: 1.01-1.12), P = 0.023) and nadir PRL levels (aOR:0.97 (95% CI: 0.94-0.99), P = 0.019) at 3-6 months. ROC analyses revealed that an early tumor shrinkage cut-off rate of 44.9% (88% sensitivity, 62% specificity) and an early PRL cut-off level of 30 ng/mL (75% sensitivity, 77% specificity) were identified as effective follow-up parameters to predict GR in the first-year. The median available follow-up duration for the patients was 23.5 (17.0-48.0) months. All GRs maintained PRL normalization and ≥50% tumor volume reduction, while 33.3% and 42.9% of PRs failed to meet these goals, respectively, at the last visit (P = 0.009, P = 0.002). Three of the PRs required surgery during follow-up.

Conclusion: Approximately half of invasive macroprolactinoma patients achieved the composite goal within one year of cabergoline therapy. Early follow-up studies, rather than baseline characteristics, are strong predictors of treatment success. In the early assessments at 3-6 months of these symptomatic invasive tumors under cabergoline treatment, cases with PRL levels of 30 ng/mL or lower, or tumor shrinkage of 45% or more, are highly unlikely to require surgery in the first year or subsequent visits.