Giant prolactinomas larger than 60 mm in size: a cohort of massive and aggressive prolactin-secreting pituitary adenomas

Prolactinomas account for approximately 40% of all pituitary adenomas and are an important cause of hypogonadism and infertility. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism through the normalization of hyperprolactinemia and control of tumor mass. Medical therapy with dopamine agonists is highly effective in the majority of cases and represents the mainstay of therapy. Recent data indicating successful withdrawal of these agents in a subset of patients challenge the previously held concept that medical therapy is a lifelong requirement. Complicated situations, such as those encountered in resistance to dopamine agonists, pregnancy, and giant or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both. Progress in elucidating the mechanisms underlying the pathogenesis of prolactinomas may enable future development of novel molecular therapies for treatment-resistant cases. This review provides a critical analysis of the efficacy and safety of the various modes of therapy available for the treatment of patients with prolactinomas with an emphasis on challenging situations, a discussion of the data regarding withdrawal of medical therapy, and a foreshadowing of novel approaches to therapy that may become available in the future.

Gender differences in tumor size are supposed to exist in hyperprolactinemia since microadenomas are more commonly found in women and macroadenomas in men. Whether this reflects only a delay in diagnosis in men or a true gender difference in tumor pathogenesis is still unclear. To prospectively analyze gender differences in the presentation and response to cabergoline treatment in 219 consecutive newly diagnosed patients with hyperprolactinemia. An open prospective design. Of the 219 patients of which 145 were women; 107 patients had macroprolactinoma, 97 had microprolactinoma, and 15 had non-tumoral hyperprolactinemia. Presenting clinical symptoms, prolactin levels and tumor size at magnetic resonance imaging were measured before and 3-6 Months after cabergoline therapy. Prevalence of microprolactinomas (56% vs 22%, P=<0.0001) and non-tumoral hyperprolactinemia (10% vs 0%, P=0.01) was higher in women than in men. Men and women were of similar age (median 32 vs 29 Years; P=0.2) and a similar number had gonadal/sexual dysfunction (85 vs 83%, P=0.6); weight gain (70 vs 46%; P=<0.0001) and galactorrhea (52 vs 19%; P=<0.0001) were more common in women. Prolactin levels were higher in men than in women, whether exhibiting macro- (2848+/-2954 vs 1132+/-2351 microg/l, P=<0.0001) or microadenomas (187.8+/-51.8 vs 135.4+/-60.5 microg/l, P=0.009) and the size of the adenoma was larger in men than in women irrespective of macro- (25.8+/-12.4 vs 17.2+/-7.2 mm, P=<0.0001) or microadenoma diagnosis (8.0+/-1.4 vs 7.1+/-1.6 mm, P=0.04). After treatment, prolactin levels decreased by 89.2-96.4% in all groups, and normalized more frequently in micro- than in macroadenoma patients (86 vs 64%, P<0.0001), regardless of gender (70% vs 69%, P=0.9). Menses resumed in 82% of women, libido disturbances improved in 57% of men. Tumor size was reduced by 45+/-25% and 52+/-24% in macroprolactinoma patients and by 44+/-31 and 38+/-29% in microprolactinoma patients in women and men respectively. Visual field defects disappeared in 61% of women and in 71% of men (P=0.6). Prevalence of macroprolactinomas was similar in men and women; microprolactinomas and non-tumoral hyperprolactinemia were more frequent in women. Clinical symptoms at presentation differed according to gender, with galactorrhea and weight gain more frequent in women. The successful response to cabergoline treatment for 6 Months was higher in micro- than in macroprolactinoma patients and was similar in women and men.

Giant prolactinomas are rare tumours, representing only 2-3% of all prolactin (PRL)-secreting tumours and raising special diagnostic and therapeutic challenges. Based on several considerations developed in this review, their definition should be restricted to pituitary adenomas with a diameter of 40  mm or more, significant extrasellar extension, very high PRL concentrations (usually above 1000  μg/l) and no concomitant GH or ACTH secretion. Giant prolactinomas are much more frequent in young to middle-aged men than in women, with a male to female ratio of about 9:1. Endocrine symptoms are often present but overlooked for a long period of time, and diagnosis is eventually made when neurologic complications arise from massive extension into the surrounding structures, leading to cranial nerve palsies, hydrocephalus, temporal epilepsy or exophthalmos. PRL concentrations are usually in the range of 1000-100,000  μg/l, but may be underestimated by the so-called 'high-dose hook effect'. As in every prolactinoma, dopamine agonists are the first-line treatment allowing rapid alleviation of neurologic symptoms in the majority of the cases, a significant reduction in tumour size in three-fourths of the patients and PRL normalization in 60-70%. These extensive tumours are usually not completely resectable and neurosurgery has significant morbidity and mortality. It should therefore be restricted to acute complications such as apoplexy or leakage of cerebrospinal fluid (often induced by medical treatment) or to patients with insufficient tumoural response or progression. Irradiation and temozolomide are useful adjuvant therapies in a subset of patients with aggressive/invasive tumours, which are not controlled despite combined medical and surgical treatments. Because of these various challenges, we advocate a multidisciplinary management of these giant tumours in expert centres. © 2014 European Society of Endocrinology.