Stereotactic Radiation Therapy in Pituitary Adenomas, is it Better than Conventional Radiation Therapy

Abstract

Pituitary radiotherapy (RT) has undergone important progress in the last decades due to the development of new stereotactic techniques which provide more precise tumour targeting with less overall radiation received by the adjacent brain structures. Pituitary surgery is usually firstline therapy in most patients with nonfunctioning (NFPA) and functioning adenomas (except for prolactinomas and large growth hormone (GH) secreting adenomas), while RT is used as second or third-line therapy. The benefits of RT (tumour volume control and, in functional tumours, decreased hormonal secretion) are hampered by the long latency of the effect and the potential side effects. This review presents the updates in the efficacy and safety of the new stereotactic radiation techniques in patients with NFPA, GH-, ACTH-or PRL-secreting pituitary adenomas. Methods. A systematic review was performed using PubMed and articles/abstracts and reviews detailing RT in pituitary adenomas from 2000 to 2017 were included. Results. Stereotactic radiosurgery (SRS) and fractionated stereotactic RT (FSRT) provide high rates of tumour control i.e. stable or decrease in tumour size, in all types of pituitary adenomas (median 92-98%) at 5 years. Endocrinological remission is however significantly lower: 44-52% in acromegaly, 54-64% in Cushing's disease and around 30% in prolactinomas at 5 years. The rate of new hypopituitarism varies from 10% to 50% at 5 years in all tumour types and as expected increases with the duration of follow-up (FU). The risk for other radiation-induced complications is usually low (0-5% for new visual deficits, cranial nerves damage or brain radionecrosis and extremely low for secondary brain tumours), however longer FU is needed to determine rates of secondary tumours. Notably, in acromegaly, there may be a higher risk for stroke with FSRT. Conclusion. Stereotactic radiotherapy can be an effective treatment option for patients with persistent or recurrent pituitary adenomas after unsuccessful surgery (especially if residual tumour is enlarging) and/or resistance or unavailability of medical therapy. Comparison with conventional radiation therapy (CRT) is rather difficult, due to the substantial heterogeneity of the studies. In order to evaluate the potential brain-sparing effect of the new stereotactic techniques, suggested by the current data, longterm studies evaluating secondary morbidity and mortality are needed.

Aggressive Pituitary Adenoma Not Fulfilling the New High-Risk Criteria with Progression after 18-Year Stable Clinical Course: Case Report

“…[18][19][20][21][22][23] Stereotactic radiosurgery, including Gamma Knife surgery, has been devised to ensure better disease control than conventional irradiation. [24][25][26] We previously reported the potential efficacy of Gamma Knife surgery to control residual tumor with high K i -67 labeling index after transsphenoidal adenomectomy. 27 However, the prognosis is extremely poor for patients not indicated for Gamma Knife radiosurgery.…”

Tercer Consenso Nacional de Acromegalia: recomendaciones para su diagnóstico, tratamiento y seguimiento

“…Es una terapia efectiva para el control tumoral y bioquímico 86 . Con el avance en el tratamiento médico ha quedo como terapia de tercera línea; sin embargo, en los últimos años la RT ha tenido un importante avance con el advenimiento de nuevas técnicas que permiten mayor precisión para localizar el tumor, minimizando la radiación al resto del parénquima cerebral 87 .…”

“…La RT es una terapia rentable a largo plazo 91,93 . A diferencia a lo observado con el uso de terapia médica, la granulación no es un factor pronóstico de respuesta a RT 85,87 .…”

“…Una de las principales desventajas es el tiempo de latencia para control bioquímico, que va de 2 a 15 años, por lo cual deberá otorgarse tratamiento médico en espera de respuesta al tratamiento 85 . Existe controversia respecto a si durante la RT se debe suspender el tratamiento médico, pues podría disminuir la efectividad de esta 85,87 . Debido a que la literatura es controvertida hasta el momento, no está indicado suspender el tratamiento médico 10 .…”

Updates in the Medical Treatment of Pituitary Adenomas

“…Radiation therapy is viewed as a third-line treatment for prolactinomas [1], increasingly given in a single high dose fraction [8]. Partial endocrine response ranges from 22-100 % while endocrine normalization ranges from 0-60 %, with a median of approximately 30 % [41,42]. Due to high rates of hypopituitarism, radiation therapy is usually reserved when both medication and surgery (or surgeries) have failed [8].…”