Treatment paradigms for pituitary adenomas: defining the roles of radiosurgery and radiation therapy

Surgical management of adrenocorticotropic hormone-secreting pituitary adenomas

Cushing's disease is defined as hypercortisolemia caused by secretion of adrenocorticotropic hormone from a pituitary adenoma. The diagnosis of Cushing's disease is based on clinical symptoms, laboratory and imaging findings. Once an adrenocorticotropic-hormone-secreting adenoma is found, the standard of care is transsphenoidal adenomectomy. MRI negative microadenomas and large, invasive macroadenomas provide a surgical and clinical challenge and are best handled at high volume centers. Multiple options exist for refractory disease or recurrence, including repeat surgery, radiosurgery and radiotherapy, medical management and bilateral adrenalectomy.

The Treatment of Cushing's Disease

Cushing's disease (CD), or pituitary-dependent Cushing's syndrome, is a severe endocrine disease caused by a corticotroph pituitary tumor and associated with increased morbidity and mortality. The first-line treatment for CD is pituitary surgery, which is followed by disease remission in around 78% and relapse in around 13% of patients during the 10-year period after surgery, so that nearly one third of patients experience in the long-term a failure of surgery and require an additional second-line treatment. Patients with persistent or recurrent CD require additional treatments, including pituitary radiotherapy, adrenal surgery, and/or medical therapy. Pituitary radiotherapy is effective in controlling cortisol excess in a large percentage of patients, but it is associated with a considerable risk of hypopituitarism. Adrenal surgery is followed by a rapid and definitive control of cortisol excess in nearly all patients, but it induces adrenal insufficiency. Medical therapy has recently acquired a more important role compared to the past, due to the recent employment of novel compounds able to control cortisol secretion or action. Currently, medical therapy is used as a presurgical treatment, particularly for severe disease; or as postsurgical treatment, in cases of failure or incomplete surgical tumor resection; or as bridging therapy before, during, and after radiotherapy while waiting for disease control; or, in selected cases, as primary therapy, mainly when surgery is not an option. The adrenal-directed drug ketoconazole is the most commonly used drug, mainly because of its rapid action, whereas the glucocorticoid receptor antagonist, mifepristone, is highly effective in controlling clinical comorbidities, mainly glucose intolerance, thus being a useful treatment for CD when it is associated with diabetes mellitus. Pituitary-directed drugs have the advantage of acting at the site responsible for CD, the pituitary tumor. Among this group of drugs, the dopamine agonist cabergoline and the somatostatin analog pasireotide result in disease remission in a consistent subgroup of patients with CD. Recently, pasireotide has been approved for the treatment of CD when surgery has failed or when surgery is not an option, and mifepristone has been approved for the treatment of Cushing's syndrome when associated with impairment of glucose metabolism in case of the lack of a surgical indication. Recent experience suggests that the combination of different drugs may be able to control cortisol excess in a great majority of patients with CD.

Management of macroprolactinomas

Prolactin (PRL) secreting tumors are the most common functional neoplasms of the pituitary and are commonly subdivided into microprolactinomas (<10 mm) and macroprolactinomas (≥10 mm) according to their baseline diameter. Patients with prolactinoma present with symptoms evolving from hyperprolactinemia and with those caused by pressure of the expanding mass on surrounding tissues, including the optic chiasm and the cavernous sinuses. We hereby describe the possible complications of macroprolactinomas, including mass effects, hypopituitarism, CSF leak and apoplexy and discuss their relevant management.

In general, all patients harboring macroprolactinomas should be treated, the objectives being to achieve normal or near normal PRL levels, to reduce or stabilize adenoma size and to recover altered pituitary axes. Medical therapy with dopamine agonists (DA) is the preferred initial treatment for the vast majority of patients harboring prolactinomas. Pituitary surgery is indicated in patients who cannot tolerate or are resistant to therapy with DAs, patients that seek fertility and harbor adenomas that impinge on the optic chiasm, psychiatric patients with contraindication to DA treatment and patients presenting with pituitary apoplexy or a cerebrospinal fluid (CSF) leak. In addition, in this review, several patient populations with unique clinical characteristics will be discussed separately namely postmenopausal women, the elderly, children and patients with pituitary carcinoma.

Cushing’s disease: the clinical features, diagnostics, differential diagnostics, and methods of treatment

The present guidelines on diagnostics, differential diagnostics, and methods of treatment of Cushing’s disease have been developed by a group of Russian specialists.

Stereotactic radiation therapy for skull base recurrences: Is a salvage approach still possible?

AIM

A literature review was performed to analyse the role of stereotactic radiotherapy given in a single shot or in a fractionated fashion for recurrent skull base tumours in order to ascertain if it can be a real salvage approach.

BACKGROUND

The management of recurrent skull base tumours can have a curative or palliative intent and mainly includes surgery and RT.

MATERIALS AND METHODS

One-thousand-ninety-one articles were found in the search databases and the most relevant of them were analysed and briefly described.

RESULTS

Data on recurrences of meningioma, pituitary adenoma, craniopharyngioma, chordoma and chondrosarcoma, vestibular schwannoma, glomus jugulare tumours, olfactory neuroblastoma and recurrences from head and neck tumours invading the base of skull are reported highlighting the most relevant results in terms of local control, survival, side effects and complications.

CONCLUSIONS

In conclusion, it emerges that SRS and FSRT are effective and safe radiation modalities of realize real salvage treatment for recurrent skull base tumours.

Aggressive pituitary adenomas--diagnosis and emerging treatments

The WHO categorizes pituitary tumours as typical adenomas, atypical adenomas and pituitary carcinomas, with typical adenomas constituting the major class. However, the WHO classification does not provide an accurate correlation between histopathological findings and clinical behaviour. Tumours lacking typical histological features are classified as atypical, but not all are clinically atypical or exhibit aggressive behaviour. Pituitary carcinomas, by definition, have craniospinal or systemic metastases, although not all display classical cytological features of malignancy. Aggressive pituitary adenomas, defined from a clinical perspective, have earlier and more frequent recurrences and can be resistant to conventional treatments. Specific biomarkers have not yet been identified that can distinguish between clinically aggressive and nonaggressive pituitary adenomas, although the antigen Ki-67 proliferation index might be of value. This Review highlights the need to develop new biomarkers to facilitate the early detection of clinically aggressive pituitary adenomas and discusses emerging markers that hold promise for their identification. Defining aggressiveness is of crucial importance for improving the management of patients by enhancing prognostic predictions and effectiveness of treatment. New drugs, such as temozolomide, have potential use in the management of these patients; anti-VEGF therapy, mTOR and tyrosine kinase inhibitors are also potentially useful in managing selected patients.