PMON120 Clinical Course Of Untreated Giant Invasive Macroprolactinomas- A Case Series

Abstract Introduction Giant invasive prolactinomas are rare pituitary tumours and have a male preponderance of 9: 1. In majority of cases, dopamine agonists (DA) are the treatment of choice in lowering prolactin and tumour shrinkage. Surgery may be opted in those with acute compressive symptoms or visual loss. Prolactinomas are known to invade the sellar floor, sphenoid sinus and clivus. Spontaneous CSF leak is rare in untreated patients with invasive prolactinomas compared to those on DA who respond with rapid tumour shrinkage that causes unplugging of the conduits resulting in CSF rhinorrhoea. We present 5 male patients with untreated giant invasive prolactinomas with skull base destruction where close surveillance was opted over DA treatment. Results Five male patients with median age of 73±10 years were studied. 1 patient presented with headache, vomiting and 6th nerve palsy which spontaneously resolved over weeks. 2 patients were diagnosed during work up of other hormonal deficiencies and in 2 patients giant tumours were incidentally found on imaging for head injury. Prolactin values ranged from 55,641 to 835,800 mIU/L. Hormonal deficiency was present in 3/5; anterior hypopituitarism (1) and symptomatic secondary hypogonadism (2). MRI imaging in all patients showed extensive skull base bony erosion, with tumour invasion into sphenoid sinus and clivus. Additionally, the patient with largest tumour had invasion into right orbital roof and floor of right anterior cranial fossa. In other patients, tumour had also invaded occipital condyles (1), bilateral cavernous sinus (1). All patients were discussed in tertiary neurosurgical MDT. As the risk of CSF leakage due to tumour shrinkage outweighed the benefits of tumour reduction, a decision not for medical treatment was agreed with patients and planned for active surveillance with MRI scans and regular clinical and visual fields assessments. The mean follow-up period was 4±1 years. One patient was very frail and decided not for radiological surveillance. DA treatment is being considered for the patient with the largest tumour which has grown further causing frontal lobe invasion. There was no significant tumour size increase in other 4 patients and none had spontaneous CSF leak. Discussion Risk stratification for CSF leak with DA treatment is difficult as it depends on the invasion, tumour response to DAs and the extent of underlying bony destruction. This may cause a dilemma on whether or not to treat some patients with DAs. The risk of CSF leak, bacterial meningitis and the subsequent need for urgent surgical repair may outweigh the benefits of tumour reduction with DAs particularly in some patients with low symptom burden. In our experience, patient counselling, active radiological surveillance and considering treatment with change in symptoms (visual deterioration, compressive pathology) could be an appropriate management option in such patients. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.