Endocrine Abstracts

Background: Pituitary tumours (PT) are generally benign, but they can rarely show an aggressive behaviour, invade surrounding structures and/or grow/recur despite multimodal treatment, making their management extremely challenging. According to the latest guidelines, temozolomide (TMZ) can be an option after failure of standard therapies in aggressive PT, while little data are available on alternative approaches such as peptide receptor radionuclide therapy (PRRT). Herein we report on the effectiveness, safety and long-term outcome of PRRT in three patients with aggressive giant PT, also reviewing data from literature.

Patients and methods: Two patients (1 F, 1 M) were affected by giant prolactinoma, and one (F) by a non-functioning pituitary adenoma (NFPA). Patient #1 received 5 cycles of ¹¹¹In-DTPA-octreotide (total dose 37 GBq) over a 23-month period, after unsuccessful surgery and long-term dopamine-agonist treatment. Patient #2 underwent 2 cycles (12.6 GBq) of PRRT with ¹⁷⁷Lu-DOTATOC, after failure of multiple surgeries, radiosurgery and TMZ. In Patient #3, five cycles (29.8 GBq) of ¹⁷⁷Lu-DOTATOC were administered after five unsuccessful trans-sphenoidal approaches, radiotherapy and TMZ. A systematic review of the current literature retrieved nine more cases of aggressive PT treated with PRRT.

Results: PRRT was successful in patient #1, leading to significant shrinkage of the tumor (from 63 to 3.1 cc) and remarkable visual/neurological amelioration over an eight-year follow-up period. Patient #2 and #3 did not take advantage from treatment, since PT continued to grow leading to blindness and neuro-cognitive disorders in patient #2, and monolateral amaurosis in patient #3. No PRRT-related adverse effects were reported in any subject. Overall, also including 9 patients reported in literature (3 carcinomas and 6 adenomas), PRRT induced tumor shrinkage and clinical/biochemical improvement in 4/11 patients (36.3%). Response to PRRT did not correlate with gender or age of patients, neither with radionuclide or peptide used for treatment, but PRRT failure was significantly associated with previous TMZ treatment. Overall, PRRT was well tolerated and significant adverse effects were reported only in 2 patients (18.2%).

Conclusions: PRRT induced PT shrinkage and clinical and/or biochemical improvement in one-third of patients with aggressive PT overall, and in 80% of those not previously treated with TMZ. PRRT is a safe therapeutic option when surgery and radiosurgery fail to control PT progression. However, at present, considering the few available studies, PRRT should be proposed for aggressive PT only in an experimental setting, after conventional therapies.