Endocrine Abstracts

Introduction: Parasellar extension of macroprolactinomas defined on imaging criteria was reported to be an independent predictor of hormonal resistance to dopamine agonists (DA).

Methods: Two hundred and twelve patients with macroprolactinomas (87 M/125 F), treated with DA for 5 years median period; prolactin (fluoroimmunoassay or chemiluminescence), CT scan and/or MRI with contrast agents were performed; maximum diameter evolution was reported.

Results: Parasellar extension or giant tumors (≥4 cm) were encountered in 71 patients (33.5%) – group A, while 141 tumors formed group B. According to prolactin normalization, patients were classified into cured patients (n=16), pseudo-cured patients (recurrence of hyperprolactinemia after DA withdrawal) (n=11), patients responsive to DA, but not fulfilling the criteria for DA withdrawal (n=157), patients initially resistant to DA therapy (n=28). Patients responsive to DA (cured, pseudo-cured and responsive) had significant lower prevalence of parasellar extension (57/184, 30.9%) versus patients resistant to DA (15/28, 53.6%), P=0.02. Within responsive group, prevalence of parasellar extension and giant tumors was similar between cured patients (4/16, 25%), pseudo-cured patients (3/11, 27.3%), and responsive patients (50/157, 31.8%), P=NS. Regarding tumor volume outcome, tumor shrinkage ≥50% or small residual necrotic tumor was noticed significantly more frequent in group A (40/71, 56.3%) versus group B (49/141, 34.8%), P=0.003; complete disappearance of tumor, tumor shrinkage <50%, stationery tumor and tumor increase were similar in both A, B groups.

Conclusion: Parasellar extension and/or tumor size over 4 cm are associated in macroprolactinomas with resistance of prolactin normalization on dopamine agonist therapy, but not with resistance to tumor shrinkage.