Endocrine Abstracts

Non-functioning pituitary adenomas (NFPA) are the second most common variant of pituitary tumors. They are presented by compression symptoms, hypopituitarism and in rec as incidental findings during brain imaging. When symptomatic, primary therapy for NFPAs is surgery most commonly by the trans-sphenoidal (TSS) approach. Medical therapy is not generally recommended in this setting, particularly when immediate decompression of the optic chiasm is needed. Despite the debulking efficacy of TSS, in many occasions only partial tumor resection is achieved. Recurrence rates are high in partially resected tumors. Although less frequently, even completely resected tumors may also recur. Therefore, there is a need for post-surgical surveillance and intervention in order to prevent recurrence. The current practice in most centers is to follow-up the pituitary lesion by MRI-imaging and offer additional therapy, usually in the form of radiotherapy (RT), in case of recurrence. RT, either conventional or stereotactic, is effective in controlling further tumor growth but its use is compromised by significant side effects. Based on findings that many NFPAs demonstrate expression of dopamine and somatostatin receptors, medical therapy with dopamine agonists (DA) and somatostatin analogues (SSA) have been used after surgery in order to prevent recurrence. So far, DAs have been more widely tested showing some promise in several small-scale case series. In a recent larger study, introduction of DA immediately after surgery led to a lower number of recurrences compared to a control group that did not receive DA therapy. However, since not all patients will recur, such a strategy exposes a substantial number of patients to unnecessary long-term DA therapy. Unfortunately there are no robust predictors for tumor recurrence. In fact, the best predictor of tumor growth is growth itself. However, DA therapy was less effective when introduced later in patients that already demonstrated a tendency for tumor regrowth. Surprisingly the beneficial effect of DA therapy does not correlate with dopamine receptor expression. This finding raises concerns about the pathophysiological background of the observed DA benefit. Moreover, there are no solid data on hard end points e.g. prevention of visual fields defects and avoidance of second surgery. Although early initiation of treatment may be preferable, dosage and duration of treatment are largely empirical. The need for higher doses and long treatment periods raises some safety concerns. Definitely a well-designed randomized control trial will resolve many of these issues. However, the lack of industrial interest and the long time-length required to obtain valid data, limits the feasibility of such a perspective. To summarize, the promise of most medications is limited by imprecisions regarding the final outcome and uncertainties on dosing and duration of preventive therapy. So far, effective medications have rendered prolactinomas and acromegaly well manageable disorders. For NFPAs such a possibility still remains elusive.