Endocrine Abstracts

JOINT2476

Objective: To assess the characteristics of patients with resistant prolactinomas and adjuvant treatment modalities in practice.

Materials and methods: A total of 33 patients (20 men, 13 women) with resistant prolactinomas were studied, focusing on age at diagnosis, prolactin (PRL) levels and adenoma size and characteristics.

Results: The median age at diagnosis was 30 years for men and 25 years for women, with no significant difference (ρ = 0.543). Men had significantly higher PRL levels (median: 12,375 mU/l)compared to women (median: 2,175 mU/L), P < 0.001. Microadenomas were more frequent in women (38% vs 10% in men, P = 0.051), while macroadenomas were more common in men (85% vs 54%, P = 0.05). A significant positive correlation was found between the initial PRL level and the three adenoma dimensions: vertical (ρ=0.616, P < 0.001), horizontal (ρ = 0.581, P = 0.002) and anteroposterior (ρ = 0.761, P < 0.001), with correlation strength increasing from the first to the third size. In patients with microadenomas, the median PRL level was 1,500 mU/l, eight times lower than in macroadenomas (median: 12,000 mU/l, P < 0.05). Tumor growth was intracellar in 75.8%, suprasellar in 60.6%, parasellar in 45.5%, and infrasellar in 30.3%. Hypogonadism was found in 15 men and 10 women, with no significant gender differences (P > 0.05). Adrenal insufficiency (2/17) and secondary hypothyroidism (1/11) were rare, with no growth hormone deficiency. Cabergoline therapy significantly decreased PRL levels in the overall patient sample (P = 0.003) and in men (P < 0.001), but had no significant effect in women (P = 0.866). It notably reduced the vertical size of adenomas (P = 0.011), but had no effect on horizontal or anteroposterior sizes (P = 0.410 and P =0.779). Adjuvant therapy was used in 10 patients, including tamoxifen (4), tamoxifen with bromocriptine (2), tamoxifen with cabergoline (3), and temozolomide with cabergoline (1).

Conclusions: Resistance to dopamine agonists is more common in younger patients, with men having higher PRL levels due to macroadenomas. PRL levels strongly correlate with the anteroposterior size of the adenoma. Cabergoline significantly lowers PRL levels in men, with no significant changes in women, possibly due to lower baseline levels or gender-related treatment differences. It reduces the vertical adenoma size without affecting the horizontal or anteroposterior dimensions, suggesting selective action on tumor volume. Adjuvant treatment options in real clinical practice remain highly limited. Further research into resistance mechanisms and personalized treatment is needed.