Gamma Knife radiosurgery for pituitary adenomas

Dose to neuroanatomical structures surrounding pituitary adenomas and the effect of stereotactic radiosurgery on neuroendocrine function: an international multicenter study

OBJECTIVE

Stereotactic radiosurgery (SRS) provides a safe and effective therapeutic modality for patients with pituitary adenomas. The mechanism of delayed endocrine deficits based on targeted radiation to the hypothalamic-pituitary axis remains unclear. Radiation to normal neuroendocrine structures likely plays a role in delayed hypopituitarism after SRS. In this multicenter study by the International Radiosurgery Research Foundation (IRRF), the authors aimed to evaluate radiation tolerance of structures surrounding pituitary adenomas and identify predictors of delayed hypopituitarism after SRS for these tumors.

METHODS

This is a retrospective review of patients with pituitary adenomas who underwent single-fraction SRS from 1997 to 2019 at 16 institutions within the IRRF. Dosimetric point measurements of 14 predefined neuroanatomical structures along the hypothalamus, pituitary stalk, and normal pituitary gland were made. Statistical analyses were performed to determine the impact of doses to critical structures on clinical, radiographic, and endocrine outcomes.

RESULTS

The study cohort comprised 521 pituitary adenomas treated with SRS. Tumor control was achieved in 93.9% of patients over a median follow-up period of 60.1 months, and 22.5% of patients developed new loss of pituitary function with a median treatment volume of 3.2 cm3. Median maximal radiosurgical doses to the hypothalamus, pituitary stalk, and normal pituitary gland were 1.4, 7.2, and 11.3 Gy, respectively. Nonfunctioning adenoma status, younger age, higher margin dose, and higher doses to the pituitary stalk and normal pituitary gland were independent predictors of new or worsening hypopituitarism. Neither the dose to the hypothalamus nor the ratio between doses to the pituitary stalk and gland were significant predictors. The threshold of the median dose to the pituitary stalk for new endocrinopathy was 10.7 Gy in a single fraction (OR 1.77, 95% CI 1.17-2.68, p = 0.006).

CONCLUSIONS

SRS for the treatment of pituitary adenomas affords a high tumor control rate with an acceptable risk of new or worsening endocrinopathy. This evaluation of point dosimetry to adjacent neuroanatomical structures revealed that doses to the pituitary stalk, with a threshold of 10.7 Gy, and doses to the normal gland significantly increased the risk of post-SRS hypopituitarism. In patients with preserved pre-SRS neuroendocrine function, limiting the dose to the pituitary stalk and gland while still delivering an optimal dose to the tumor appears prudent.

Efficacy and Safety of Stereotactic Radiotherapy in Cushing's Disease: A Single Center Experience

OBJECTIVE

To determine the efficacy and safety of stereotactic radiotherapy (RT) in patients with Cushing's disease (CD).

METHODS

The study included 38 patients [31 patients who received gamma knife radiosurgery (GKS) and 7 patients who received cyberknife hypofractionated RT (HFRT)] with CD. Hormonal remission was considered if the patient had suppressed cortisol levels after low dose dexamethasone, normal 24-hour urinary free cortisol (UFC), and lack or regression of clinical features.

RESULTS

Biochemical control after RT was observed in 52.6% of the patients with CD and median time to hormonal remission was 15 months. Tumor size control was obtained in all of the patients. There was no significant relationship between remission rate and laboratory, radiological and pathological variables except for preoperative UFC. Remission rate was higher in patients with lower preoperative UFC. Time to remission increased in parallel to postoperative cortisol and 1mg DST level. Although medical therapy before RT did not affect the rate of- and time to remission, medical therapy after RT prolonged the time to hormonal remission.

CONCLUSION

In this current single center experience, postoperative cortisol and 1mg DST levels were found as the determinants of time to remission. Although medical therapy before RT did not affect the rate of- and time to remission, medical therapy after RT prolonged the time to biochemical control . This latter finding might suggest a radioprotective effect of cortisol lowering medication use on peri-RT period.

Role of gamma knife radiosurgery in the treatment of prolactinomas

PURPOSE

Stereotactic radiosurgery is one of the treatment options for prolactinomas, the most commonly used being Gamma Knife Radiosurgery (GKRS). GKRS is indicated mainly in the treatment of dopamine agonist (DA)-resistant prolactinomas. In our study, we report on our experience in treating prolactinoma patients by GKRS.

METHODS

Twenty-eight patients were followed-up after GKRS for 26-195 months (median 140 months). Prior to GKRS, patients were treated with DAs and 9 of them (32.1%) underwent previous neurosurgery. Cavernous sinus invasion was present in 16 (57.1%) patients. Indications for GKRS were (i) resistance to DA treatment (17 patients), (ii) drug intolerance (5 patients), or (iii) attempts to reduce the dosage and/or shorten the length of DA treatment (6 patients).

RESULTS

After GKRS, normoprolactinaemia was achieved in 82.1% of patients, out of which hormonal remission (normoprolactinaemia after discontinuation of DAs) was achieved in 13 (46.4%), and hormonal control (normoprolactinaemia while taking DAs) in 10 (35.7%) patients. GKRS arrested adenoma growth or decreased adenoma size in all cases. Two patients (8.3%) developed hypopituitarism after GKRS. Prolactinoma cystic transformation with expansive behaviour, manifested by bilateral hemianopsia, was observed in one patient.

CONCLUSIONS

GKRS represents an effective treatment option, particularly for DA-resistant prolactinomas. Normoprolactinaemia was achieved in the majority of patients, either after discontinuation of, or while continuing to take, DAs. Tumour growth was arrested in all cases. The risk of the development of hypopituitarism can be limited if the safe dose to the pituitary and infundibulum is maintained.

Radiation dose to neuroanatomical structures of pituitary adenomas and the effect of Gamma Knife radiosurgery on pituitary function

OBJECTIVE

Gamma Knife radiosurgery (GKRS) provides a safe and effective management option for patients with all types of pituitary adenomas. The long-term adverse effects of targeted radiation to the hypothalamic-pituitary axis in relationship to radiation dose remain unclear. In this retrospective review, the authors investigated the role of differential radiation doses in predicting long-term clinical outcomes and pituitary function after GKRS for pituitary adenomas.

METHODS

A cohort of 236 patients with pituitary tumors (41.5% nonfunctioning, 58.5% functioning adenomas) was treated with GKRS between 1998 and 2015. Point dosimetric measurements, with no minimum volume, to 14 consistent points along the hypothalamus bilaterally, pituitary stalk, and normal pituitary were made. Statistical analyses were performed to determine the impact of doses to critical structures on clinical, radiological, and endocrine outcomes.

RESULTS

With a median follow-up duration of 42.9 months, 18.6% of patients developed new loss of pituitary function. The median time to endocrinopathy was 21 months (range 2-157 months). The median dose was 2.1 Gy to the hypothalamus, 9.1 Gy to the pituitary stalk, and 15.3 Gy to the normal pituitary. Increasing age (p = 0.015, HR 0.98) and ratio of maximum dose to the pituitary stalk over the normal pituitary gland (p = 0.013, HR 0.22) were independent predictors of new or worsening hypopituitarism in the multivariate analysis. Sex, margin dose, treatment volume, nonfunctioning adenoma status, or ratio between doses to the pituitary stalk and hypothalamus were not significant predictors.

CONCLUSIONS

GKRS offers a low rate of delayed pituitary insufficiency for pituitary adenomas. Doses to the hypothalamus are low and generally do not portend endocrine deficits. Patients who are treated with a high dose to the pituitary stalk relative to the normal gland are at higher risk of post-GKRS endocrinopathy. Point dosimetry to specific neuroanatomical structures revealed that a ratio of stalk-to-gland radiation dose of 0.8 or more significantly increased the risk of endocrinopathy following GKRS. Improvement in the gradient index toward the stalk and normal gland may help preserve endocrine function.

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.

Outcome of Stereotactic Radiotherapy for Patients with Uncontrolled Acromegaly

Objective:

Linear accelerator based stereotactic radiation therapy (SRT) has been used for the treatment of pituitary tumours; however, little is known concerning the use of this modality for the treatment of patients with acromegaly. We have prospectively studied the short-term outcome of SRT in 12 acromegaly patients who failed to achieve biochemical remission despite surgery and/or pharmacologic therapy.

Methods:

We identified all patients who had biochemically uncontrolled acromegaly and were treated with SRT between April 2003 and December 2006. All patients were followed prospectively based on a pre-defined protocol that included Goldman visual field examination, MRI of the sella, and pituitary hormone testing at 3, 6, 12 months, and then yearly.

Results:

A total of 12 patients with acromegaly were treated with SRT. There were 9 females and the median age of the group was 50 years. The median follow-up was 28.5 months during which time the mean tumor volume decreased by 40%, the median GH fell from 4.1 μg/L to 1.3 μg/L (p=0.003) and the median IGF-1 dropped more than half from 545.5 μg/L to 260.5 μg/L (p=0.002). Four patients achieved normal, while an additional 2 achieved near-normal, IGF-1 levels. One patient was able to discontinue and two were able to reduce their acromegaly medications while maintaining a normal IGF-1. A new pituitary hormonal deficit was found at 24 months in one patient who developed hypoadrenalism requiring corticosteroid replacement.

Conclusion:

Based on our early experience, we believe that SRT should be considered in treating patients with uncontrolled acromegaly.

Gamma knife surgery for patients with volumetric classification of nonfunctioning pituitary adenomas: a systematic review and meta-analysis

OBJECTIVE

The aim of this study was to scrutinize the literature to determine the efficacy and safety of gamma knife surgery (GKS) for the treatment of nonfunctioning pituitary adenomas (NFPAs) with volumetric classification.

METHODS

Electronic databases including MedLine, PubMed, and Cochrane Central were searched. The literature related to patients with NFPAs treated with GKS was collected. Eligible studies reported on the rate of tumor control (RTC), the rate of radiosurgery-induced optic neuropathy injury (RRIONI), the rate of radiosurgery-induced endocrinological deficits (RRIED), and other parameters.

RESULTS

A total of 17 studies met the criteria. based on the tumor volume, nfpas were divided into three groups: the RTC of group I (93 patients) with tumor volumes <2 ml was 99% (95% CI 96-100%), the RRIONI was 1% (95% CI 0-4%), and the RRIED was 1% (95% CI 0-4%). The RTC of group II (301 patients) with volumes from 2 to 4 ml was 96% (95% CI 92-99%), the RRIONI was 0 (95% CI 0-2%), and RRIED was 7% (95% CI 2-14%). The RTC of group III (531 patients) with volumes larger than 4 ml was 91% (95% CI 89-94%), the RRIONI was 2% (95% CI 0-5%), and the RRIED was 22% (95% CI 14-31%). There were significant differences in the RTC and in the RRIED among the three groups (P<0.001), indicating that there were higher RRIED and lower RTC with the increase of tumor volume.

CONCLUSIONS

NFPAs, according to tumor volume classification, need stratification for GKS treatment. GKS is the optimal choice for the treatment of group II NFPAs. Patients with residual tumor volumes of <4 ml will benefit most from GKS treatment.

Radiation-induced hypopituitarism

PURPOSE OF REVIEW

Progressive and irreversible neuro-endocrine dysfunction following radiation-induced damage to the hypothalamic-pituitary (h-p) axis is the most common complication in cancer survivors with a history of cranial radiotherapy involving the h-p axis and in patients with a history of conventional or stereotactic pituitary radiotherapy for pituitary tumours. This review examines the controversy about the site and pathophysiology of radiation damage while providing an epidemiological perspective on the frequency and pattern of radiation-induced hypopituitarism.

RECENT FINDINGS

Contrary to the previously held belief that h-p axis irradiation with doses less than 40 Gy result in a predominant hypothalamic damage with time-dependent secondary pituitary atrophy, recent evidence in survivors of nonpituitary brain tumours suggests that cranial radiation causes direct pituitary damage with compensatory increase in hypothalamic release activity. Sparing the hypothalamus from significant irradiation with sterteotactic radiotherapy for pituitary tumours does not appear to reduce the long-term risk of hypopituitarism.

SUMMARY

Radiation-induced h-p dysfunction may occur in up to 80% of patients followed long term and is often associated with an adverse impact on growth, body image, skeletal health, fertility, sexual function and physical and psychological health. A detailed understanding of pathophysiological and epidemiological aspects of radiation-induced h-p axis dysfunction is important to provide targeted and reliable long-term surveillance to those at risk so that timely diagnosis and hormone-replacement therapy can be provided.

Stereotactic radiosurgery for treatment of Cushing disease: an Australian experience

Stereotactic radiation therapy has emerged as an alternative to conventional radiotherapy for treatment of Cushing disease. The aim of this study was to investigate the efficacy and safety of this treatment. Records of patients with Cushing disease treated with stereotactic radiation were reviewed. Seventeen patients underwent stereotactic radiosurgery. Ten achieved remission after a mean of 23 (95% confidence interval, 15-31) months, and two developed hormone deficiencies.

Comprehensive review of stereotactic radiosurgery for medically and surgically refractory pituitary adenomas

Despite advances in surgical techniques and medical therapies, a significant proportion of pituitary adenomas remain endocrinologically active, demonstrate persistent radiographic disease, or recur when followed for long periods of time. While surgical intervention remains the first-line therapy, stereotactic radiosurgery is increasingly recognized as a viable treatment option for these often challenging tumors. In this review, we comprehensively review the literature to evaluate both endocrinologic and radiographic outcomes of radiosurgical management of pituitary adenomas. The literature clearly supports the use of radiosurgery, with endocrinologic remission rates and time to remission varying by tumor type [prolactinoma: 20–30%, growth hormone secreting adenomas: ~50%, adrenocorticotrophic hormone (ACTH)-secreting adenomas: 40–65%] and radiographic control rates almost universally greater than 90% with long-term follow-up. We stratify the outcomes by tumor type, review the importance of prognostic factors (particularly, pre-treatment endocrinologic function and tumor size), and discuss the complications of treatment (with special attention to endocrinopathy and visual complications). We conclude that the literature supports the use of radiosurgery for treatment-refractory pituitary adenomas, providing the patient with a minimally invasive, safe, and effective treatment option for an otherwise resistant tumor. As such, we provide literature-based treatment considerations, including radiosurgical dose, endocrinologic, radiographic, and medical considerations for each adenoma type.

Long-term outcomes after gamma knife stereotactic radiosurgery for nonfunctional pituitary adenomas

BACKGROUND

Nonfunctional pituitary adenomas (NFPAs) represent approximately 50% of all pituitary tumors.

OBJECTIVE

To evaluate the long-term outcomes of stereotactic radiosurgery for NFPAs.

METHODS

We evaluated the management outcomes of Gamma Knife radiosurgery in 125 patients with NFPAs over an interval of 22 years. The median patient age was 54 years (range, 16-88 years). One hundred ten patients (88%) had residual or recurrent tumors after ≥ 1 surgical procedures, and 17 (14%) had undergone prior fractionated radiation therapy. The median target volume was 3.5 cm3 (range, 0.4-28.1 cm3), and the median tumor margin dose was 13.0 Gy (range, 10-25 Gy).

RESULTS

Tumor volume decreased in 66 patients (53%), remained stable in 46 (37%), and increased in 13 (10.4%) during a median of 62 months (maximum, 19 years) of imaging follow-up. The actuarial tumor control rates at 1, 5, and 10 years were 99%, 94%, and 76%, respectively. Factors associated with a reduced progression-free survival included larger tumor volume (≥ 4.5 cm3) and ≥ 2 prior recurrences. Of 88 patients with residual pituitary function, 21 (24%) suffered new hormonal deficits at a median of 24 months (range, 3-114 months). Prior radiation therapy increased the risk of developing new pituitary hormonal deficits. One patient (0.8%) had a decline in visual function, and 2 (1.6%) developed new cranial neuropathies without tumor progression.

CONCLUSION

Stereotactic radiosurgery can provide effective management for patients with newly diagnosed NFPAs and for those after prior resection and/or radiation therapy.

Recent advances in pituitary tumor management

PURPOSE OF REVIEW

Advances in the neurosurgical management of pituitary tumors have included the refinement of surgical access and significant progress in navigation technology to help further reduce morbidity and improve outcome. Similarly, stereotactic radiosurgery has evolved to become an integral part in pituitary tumors not amenable to medical or surgical treatment.

RECENT FINDINGS

The evolution of minimally invasive surgery has evolved toward endoscopic versus microscopic trans-sphenoidal approaches for pituitary tumors. Debate exists regarding each approach, with advocates for both championing their cause. Stereotactic and fractional radiosurgery have been shown to be a safe and effective means of controlling tumor growth and ensuring hormonal stabilization, with longer-term data available for GammaKnife compared with CyberKnife.

SUMMARY

The advances in trans-sphenoidal surgical approaches, navigation technological improvements and the current results of stereotactic radiosurgery are discussed.

Radiation treatment strategies for acromegaly

The high morbidity and mortality associated with acromegaly can be addressed with multiple treatment modalities, including surgery, medicines, and radiation therapy. Radiation was initially delivered through conventional fractionated radiotherapy, which targets a wide area over many treatment sessions and has been shown to induce remission in 50%&#x2013;60% of patients with acromegaly. However, conventional fractionated radiotherapy takes several years to achieve remission in patients with acromegaly and carries a risk of hypopituitarism that may limit its use. Stereotactic radiosurgery, of which there are several forms, including Gamma Knife surgery, CyberKnife therapy, and proton beam therapy, offers slightly attenuated efficacy but achieves remission in less time and provides more precise targeting of the adenoma with better control of the dose of radiation received by adjacent structures such as the pituitary stalk, pituitary gland, optic chiasm, and cranial nerves in the cavernous sinus. Of the forms of stereotactic radiosurgery, Gamma Knife surgery is the most widely used and, because of its long-term follow-up in clinical studies, is the most likely to compete with medical therapy for first-line adjuvant use after resection. In this review, the authors outline the major modes of radiation therapies in clinical use today, and they critically assess the feasibility of these modalities for acromegaly treatment. Acromegaly is a multisystem disorder that demands highly specialized treatment protocols including neurosurgical and endocrinological intervention. As more efficient forms of pituitary radiation develop, acromegaly treatment options may continue to change with radiation therapies playing a more prominent role.

The role of stereotactic radiosurgery in the multimodal management of growth hormone–secreting pituitary adenomas

Growth hormone (GH)–secreting pituitary adenomas represent a common source of GH excess in patients with acromegaly. Whereas surgical extirpation of the culprit lesion is considered first-line treatment, as many as 19% of patients develop recurrent symptoms due to regrowth of previously resected adenomatous tissue or to continued growth of the surgically inaccessible tumor. Although medical therapies that suppress GH production can be effective in the management of primary and recurrent acromegaly, these therapies are not curative, and lifelong treatment is required for hormonal control. Stereotactic radiosurgery has emerged as an effective adjunctive treatment modality, and is an appealing alternative to conventional fractionated radiation therapy. The authors reviewed the growing body of literature concerning the role of radiosurgical procedures in the treatment armamentarium of acromegaly, and identified more than 1350 patients across 45 case series. In this review, the authors report that radiosurgery offers true hormonal normalization in 17% to 82% of patients and tumor growth control in 37% to 100% of cases across all series, while minimizing adverse complications. As a result, stereotactic radiosurgery represents a safe and effective treatment option in the multimodal management of primary or recurrent acromegaly secondary to GH-secreting pituitary adenomas.

Radiation therapy and stereotactic radiosurgery for the treatment of Cushing's disease: an evidence-based review

PURPOSE OF REVIEW

The indications, efficacy, and safety of radiation therapy and stereotactic radiosurgery for Cushing's disease are evaluated.We queried PubMed using the terms, 'Cushing's disease', 'radiotherapy', and 'radiosurgery', then evaluated each study for the number of patients, method of radiation delivery, type of radiation therapy or radiosurgical device used, treatment parameters (e.g. maximal dose, tumor margin dose), length of follow-up, tumor-control rate, complications, rate of hormone normalization, newly onset loss of pituitary function, and method used to assess endocrine remission.

RECENT FINDINGS

A total of 39 peer-reviewed studies with 731 patients were included. The reported rates of tumor-volume control following radiotherapy and radiosurgery vary considerably from 66-100%. Additionally, the reported rates of endocrine remission vary substantially from 17-100%. The incidence of serious complications following radiosurgery is quite low. Although post-treatment hypopituitarism and disease recurrence were uncommon, they did occur, and this underscores the necessity for long-term follow-up in these patients.

SUMMARY

Radiosurgery and, in the modern era, less commonly, radiation therapy, offer both well tolerated and reasonably effective treatment for recurrent or residual Cushing's adenomas.

Gamma Knife robotic microradiosurgery of pituitary adenomas invading the cavernous sinus: treatment concept and results in 89 cases

The objective of the present retrospective study was evaluation of results of "robotic microradiosurgery" of pituitary adenomas invading the cavernous sinus. Eighty-nine patients with such tumors underwent management using Leksell Gamma Knife model C with automatic positioning system. There were 77 residual and 12 recurrent neoplasms. The applied radiosurgical treatment plan was based on the use of multiple isocenters, mainly of smaller size, which were positioned compactly within the border of the lesion with resultant improved dose homogeneity, increased average dose within the target, and sharp dose fall outside the treated volume. The marginal dose varied from 12 to 25 Gy (mean, 18.2 Gy) in non-functional pituitary adenomas (43 cases), and from 12 to 35 Gy (mean, 25.2 Gy) in hormone-secreting ones (46 cases). The length of follow-up after treatment ranged from 24 to 76 months (mean, 36 months). Control of the tumor growth was attained in 86 cases (97%), whereas actual shrinkage of the lesion was marked in 57 cases (64%). In 18 out of 46 secreting neoplasms (39%), normalization of the excess of the pituitary hormone production was noted after radiosurgery. Treatment-associated morbidity was limited to transitory cranial nerve palsy in two patients (2%). No patient with either non-functional or hormone secreting tumor exhibited new pituitary hormone deficit after treatment. In conclusion, highly precise microanatomy-based Gamma Knife robotic microradiosurgery provides an opportunity for effective management of pituitary adenomas invading the cavernous sinus with preservation of the adjacent functionally important neuronal structures.

Modern techniques for pituitary radiotherapy

Radiotherapy (RT) remains an effective treatment for residual or recurrent pituitary adenomas with excellent rates of tumour control and normalisation of excess hormone secretion. The main late toxicity is hypopituitarism: other side effects are rare. We discuss technical developments in the delivery of radiotherapy (stereotactic conformal radiotherapy (SCRT) and stereotactic radiosurgery (SRS)), all aiming to reduce the amount of normal brain receiving significant doses of radiation. We provide a comprehensive review of published data on outcome of conventional fractionated radiotherapy and modern RT techniques. SCRT is a suitable treatment technique for all sizes of pituitary adenoma and efficacy is comparable to conventional RT; the lack of long term follow up means that currently there is no information on potential reduction in the incidence of late radiation induced toxicity. Single fraction SRS can only be safely delivered to small tumours away from critical structures. There is no evidence that it produces faster decline of elevated hormone levels than fractionated treatment and is not associated with lesser morbidity.

Radiologic follow-up of non-functioning pituitary adenomas: rationale and cost effectiveness

Patients with non-functioning pituitary adenomas (NFPAs) are followed-up with serial endocrine, ophthalmologic and radiological assessment. There is a lack of evidence based guidance regarding the frequency and duration of radiological assessment during follow-up. We retrospectively analysed the details of follow-up radiological scanning in a cohort of patients diagnosed with NFPAs in an attempt to devise a rational and cost effective scanning schedule for use in routine clinical practice. 49 patients were identified using the hospital endocrine register. A detailed review of the case notes and follow up scans was undertaken. The data was analysed using descriptive statistics and Kaplan-Meier survival analysis using SPSS ver 13.0 (SPSS Inc. Chicago, IL). The time in which the tumor size in the followed up patients reached a state of 'no change' which persisted for at least two further scans was calculated. 41 patients, followed up for a median duration of 70 months were ultimately analysed. 33 patients had surgery while eight were conservatively managed. The time taken by 50% of tumors to achieve a steady state of 'no change' in tumor size on scans was 30 months. 90% of tumours achieved this state in 88 months. Surgical management did not significantly influence the time required to attain the steady state on a Kaplan-Meier analysis (Log rank test P = 0.06). NFPAs need extended follow-up since late recurrences after treatment are known. Routine radiologic follow up may be uneconomical after the steady state is achieved. Regular Goldmann perimetry beyond this time may be of greater use in selecting patients who actually need repeat surgical debulking. This method of follow up is likely to be more cost effective and reduce the number of scans performed.

Use of the Leksell gamma knife in the treatment of prolactinoma patients

OBJECTIVE

Pharmacological treatment with dopaminergic agonists (DA) is the treatment of choice for prolactinomas. Surgical and radiation treatment is also indicated in certain situations. We describe our 12-year experience in treating prolactinomas with the Leksell gamma knife (LGK).

DESIGN

We followed 35 prolactinoma patients (25.7% microprolactinomas, 74.3% macroprolactinomas) treated with LGK irradiation. The mean follow-up period was 75.5 months. Prior to LGK irradiation, patients were treated with DA and 10 of them (28.6%) underwent neurosurgery. Indications for LGK irradiation were: DA intolerance (31.4%), DA resistance (45.7%) and efforts to reduce the DA dose or shorten the period of administration (22.9%). Pituitary function was monitored regularly at 6-month intervals. The central radiation dose range was 40-80 Gy (median 70 Gy), and the minimal peripheral dose was 20-49 Gy (median 34 Gy).

RESULTS

Normoprolactinaemia was achieved in 37.1% of the patients who discontinued DA and in 42.9% of patients who continued DA treatment after LGK irradiation. The median time to prolactin normalization after discontinuation of DA was 96 months. No relapse was seen in any patient. After LGK irradiation, the prolactinoma stopped growing or decreased in size in all but one patient (97.1%).

CONCLUSION

LGK treatment resulted in normoprolactinaemia in 80.0% of the patients, all of whom had failed pharmacological treatment due to DA resistance or intolerance. After achieving normoprolactinaemia, no relapse of hyperprolactinaemia was observed in any patient. The size of the adenoma decreased even in those patients in whom it was not changed by previous DA treatment.

An approach to the management of patients with residual Cushing's disease

The evaluation and management of patients with residual Cushing’s disease is one of the more complex issues facing neurosurgeons and neuroendocrinologists in clinical practice. There is considerable controversy over several relevant issues such as the timing of the assessment of whether a patient is in remission, what biochemical parameters define remission, the most appropriate course of action to take after residual disease has been defined, etc. As a consequence of the controversies, treating physicians develop notions and fall into certain practice patterns based on evidence of varying levels, their anecdotal experiences, and information gleaned from scientific meetings. This practice pattern, we believe, constitutes the “art of medicine.” We conducted a PubMed literature search to identify manuscripts containing data relevant to Cushing’s disease, outcomes of various therapeutic modalities, and recurrences. Reference lists were used to identify additional relevant manuscripts. We focused our review on manuscripts that included reasonably large series of patients, those reflecting the experience of pituitary centers and physicians recognized as experts in the field, and those papers felt to represent seminal contributions to the literature. Furthermore, trends in the evaluation and management of relevant patients have been incorporated by the senior author who has seen and evaluated over 750 patients with documented Cushing’s syndrome over the past 18 years in clinical practice. An analysis of current evidence indicated that, despite advances in neurosurgical techniques and recent developments in adjuvant therapies, patients with residual Cushing’s disease present significant management challenges to treating physicians. In this era, however, it is indeed possible to gain control of the hypercortisolism in most patients. Despite the wide variability in research methodology designed to collect relevant data, a step-wise approach to the management of these patients can be achieved. A logical step-wise approach to the evaluation of postoperative patients with Cushing’s disease is essential. Patients with residual disease require the development of an individualized plan of management that takes into account numerous factors pertaining to status of disease, the experience of treating physicians, and available therapeutic modalities.

Stereotactic radiosurgery for pituitary adenomas: a comprehensive review of indications, techniques and long-term results using the Gamma Knife

OBJECT

This study reviews the long-term clinical results of stereotactic radiosurgery in the treatment of pituitary adenoma patients.

METHODS

We reviewed the outcomes of 298 patients who underwent Gamma Knife radiosurgery for recurrent or residual pituitary adenomas. These results are compared to other contemporary radiosurgical series.

RESULTS

Pituitary tumors are well-suited for radiosurgery, since radiation can be focused on a well circumscribed region, while adjacent neural structures in the suprasellar and parasellar regions are spared. The overall rate of volume reduction following stereotactic radiosurgery is 85% for non-secretory adenomas that are followed for more than 1-year. The rates of hormonal normalization in patients with hypersecretory adenomas can vary considerably, and tends to be higher in patients with Cushing's Disease and acromegaly (remission rate of approximately 53% and 54%, respectively) when compared with patients who have prolactinomas (24% remission) and Nelson's syndrome (29%) remission. Advances in dose delivery and modulation of adenoma cells at the time of radiosurgery may further improve results.

CONCLUSIONS

Although the effectiveness of radiosurgery varies considerably depending on the adenoma histopathology, volume, and radiation dose, most studies indicate that radiosurgery when combined with microsurgery is effective in controlling pituitary adenoma growth and hormone hypersecretion. Long-term follow-up is essential to determine the rate of endocrinopathy, visual dysfunction, hormonal recurrence, and adenoma volume control.

Gamma Knife surgery for invasive pituitary macroadenoma

OBJECT

Pituitary adenomas have been treated using a variety of modalities including resection, medication, fractionated radiotherapy, and stereotactic radiosurgery. The policy has been that all adenomas should first be treated with resection to reduce the volume of the tumor. The authors' study was conducted to determine the efficacy of using Gamma Knife surgery (GKS) for pituitary adenomas invading the cavernous sinus.

METHODS

Of 397 patients with pituitary tumors who underwent GKS between October 1994 and October 2005, 68 patients had pituitary macroadenomas invading the cavernous sinus. Sixty-seven cases were available for follow up. The mean age of the patients in these cases was 42.8 years (range 14-73 years). The male/female ratio was 0.8:1. The mean adenoma volume was 9.3 cm3. A total of 24 patients had undergone craniotomies and resection, and 11 patients had undergone transsphenoidal surgery prior to GKS. The mean follow-up period was 32.8 months. Tumor control was defined as a decrease or no change in tumor volume after GKS. Endocrinological improvement was defined as a decline in hormone levels to below 50% of the pre-GKS level. Tumor control was achieved in 95.5% of the cases. Endocrinological improvement was achieved in 68% of 25 patients. One patient suffered hypopituitarism after GKS.

CONCLUSIONS

Gamma Knife surgery is a safe and effective treatment for invasive pituitary macroadenoma with few complications.

MASEP gamma knife radiosurgery for secretory pituitary adenomas: experience in 347 consecutive cases

Background

Secretory pituitary adenomas are very common brain tumors. Historically, the treatment armamentarium for secretory pituitary adenomas included neurosurgery, medical management, and fractionated radiotherapy. In recent years, MASEP gamma knife radiosurgery (MASEP GKRS) has emerged as an important treatment modality in the management of secretory pituitary adenomas. The goal of this research is to define accurately the efficacy, safety, complications, and role of MASEP GKRS for treatment of secretory pituitary adenomas.

Methods

Between 1997 and 2007 a total of 347 patients with secretory pituitary adenomas treated with MASEP GKRS and with at least 60 months of follow-up data were identified. In 47 of these patients some form of prior treatment such as transsphenoidal resection, or craniotomy and resection had been conducted. The others were deemed ineligible for microsurgery because of body health or private choice, and MASEP GKRS served as the primary treatment modality. Endocrinological, ophthalmological, and neuroradiological responses were evaluated.

Results

MASEP GKRS was tolerated well in these patients under the follow-up period ranged from 60 to 90 months; acute radioreaction was rare and 17 patients had transient headaches with no clinical significance. Late radioreaction was noted in 1 patient and consisted of consistent headache. Of the 68 patients with adrenocorticotropic hormone-secreting(ACTH) adenomas, 89.7% showed tumor volume decrease or remain unchanged and 27.9% experienced normalization of hormone level. Of the 176 patients with prolactinomas, 23.3% had normalization of hormone level and 90.3% showed tumor volume decrease or remain unchanged. Of the 103 patients with growth hormone-secreting(GH) adenomas, 95.1% experienced tumor volume decrease or remain unchanged and 36.9% showed normalization of hormone level.

Conclusion

MASEP GKRS is safe and effective in treating secretory pituitary adenomas. None of the patients in our study experienced injury to the optic apparatus or had other neuropathies related with gamma knife. MASEP GKRS may serve as a primary treatment method in some or as a salvage treatment in the others. However, treatment must be tailored to meet the patient's symptoms, tumor location, tumor morphometry, and overall health. Longer follow-up is required for a more complete assessment of late radioreaction and treatment efficacy.

Diagnosis and treatment of prolactinomas

Prolactinomas account for approximately 40% of all pituitary adenomas. Hyperprolactinemia causes hypogonadism, infertility and galactorrhea. Macroprolactinomas may cause signs of local expansion, such as headache, visual field defects and paresis of oculomotor nerves during suprasellar and parasellar extensions. Compression of healthy pituitary tissue together with the blockade of the flow of hypothalamic released hormones to the pituitary by macroprolactinomas results in the development of hypopituitarism. The aim of treatment is restoration of hypogonadism and fertility in the microprolactinoma patients, as well as tumor shrinkage in macroprolactinoma patients. Primary therapy for prolactinomas is pharmacological treatment with dopamine agonists (DAs). However, surgical or radiation treatment is recommended for prolactinoma patients resistant or intolerant to DAs. In patients with long-term normoprolactinemia and significant tumor shrinkage, a trial of tapering and discontinuation of medical therapy is possible. After discontinuation of DAs, a long-term follow-up is necessary. In cases of recurrence displaying hyperprolactinemia and tumor enlargement, treatment must be resumed.

Hypopituitarism following radiotherapy

Deficiencies in anterior pituitary hormones secretion ranging from subtle to complete occur following radiation damage to the hypothalamic-pituitary (h-p) axis, the severity and frequency of which correlate with the total radiation dose delivered to the h-p axis and the length of follow up. Selective radiosensitivity of the neuroendocrine axes, with the GH axis being the most vulnerable, accounts for the high frequency of GH deficiency, which usually occurs in isolation following irradiation of the h-p axis with doses less than 30 Gy. With higher radiation doses (30-50 Gy), however, the frequency of GH insufficiency substantially increases and can be as high as 50-100%. Compensatory hyperstimulation of a partially damaged h-p axis may restore normality of spontaneous GH secretion in the context of reduced but normal stimulated responses; at its extreme, endogenous hyperstimulation may limit further stimulation by insulin-induced hypoglycaemia resulting in subnormal GH responses despite normality of spontaneous GH secretion in adults. In children, failure of the hyperstimulated partially damaged h-p axis to meet the increased demands for GH during growth and puberty may explain what has previously been described as radiation-induced GH neurosecretory dysfunction and, unlike in adults, the ITT remains the gold standard for assessing h-p functional reserve. Thyroid-stimulating hormone (TSH) and ACTH deficiency occur after intensive irradiation only (>50 Gy) with a long-term cumulative frequency of 3-6%. Abnormalities in gonadotrophin secretion are dose-dependent; precocious puberty can occur after radiation dose less than 30 Gy in girls only, and in both sexes equally with a radiation dose of 30-50 Gy. Gonadotrophin deficiency occurs infrequently and is usually a long-term complication following a minimum radiation dose of 30 Gy. Hyperprolactinemia, due to hypothalamic damage leading to reduced dopamine release, has been described in both sexes and all ages but is mostly seen in young women after intensive irradiation and is usually subclinical. A much higher incidence of gonadotrophin, ACTH and TSH deficiencies (30-60% after 10 years) occur after more intensive irradiation (>60 Gy) used for nasopharyngeal carcinomas and tumors of the skull base, and following conventional irradiation (30-50 Gy) for pituitary tumors. The frequency of hypopituitarism following stereotactic radiotherapy for pituitary tumors is mostly seen after long-term follow up and is similar to that following conventional irradiation. Radiation-induced anterior pituitary hormone deficiencies are irreversible and progressive. Regular testing is mandatory to ensure timely diagnosis and early hormone replacement therapy.

Radiotherapy and radiosurgery in acromegaly

Growth-hormone hypersecretion, acromegaly, is associated with reduced life expectancy. First line treatment remains surgery, but remission rates vary between 50% and 90%. In case of lack of surgical remission or recurrence, somatostatin agonists can be proposed. However, about 30% of patients are partially or totally resistant to this treatment. The growth hormone receptor antagonist pegvisomant currently needs more prolonged follow-up studies. Conventional radiotherapy and radiosurgery are two radiation treatment modalities that can be proposed to these resistant patients. Reported rates of remission for conventional radiotherapy range between 50% and 60% in patients with acromegaly, with a time to remission delayed by several years, and adverse effects including high rates of hypopituitarism. This treatment could be proposed to patients with aggressive adenomas, in whom surgery cannot allow biochemical control. In contrast, studies on stereotactic radiosurgery reported lower rates of remission, with faster growth hormone hypersecretion decline, and a lower risk of adverse effects. However, this latter technique requires a well defined target volume, which limits its indications. The high precision of this technique makes it possible to be used as an alternative primary treatment to surgery. We reviewed major advantages and drawbacks of each of these techniques, based on recent studies to try to define their respective indications in the therapeutic algorithm of acromegaly.

Radiation therapy in the treatment of pituitary tumors

✓ The treatment of pituitary tumors has progressed into a multidisciplinary approach that involves neurosurgeons, radiation oncologists, and endocrinologists. This has allowed improved outcomes in treatment of pituitary tumors due to a combination of surgical, medical, and radiation therapies. In this study, the authors review the role of radiation therapy in the treatment of pituitary adenomas.

[Radiosurgery for pituitary adenomas]

Pituitary adenomas represent nearly 15% of all intracranial tumors. Multimodal treatment includes microsurgery, medical management and radiotherapy. Microsurgery is the primary recommendation for nonfunctioning and most of functioning adenomas, except for prolactinomas that are usually managed with dopamine agonist drugs. However, about 30% of patients require additional treatment after microsurgery for recurrent or residual tumors. In these cases, fractionated radiation therapy has been the traditional treatment. More recently, radiosurgery has been established as a treatment option. Radiosurgery allows the delivery of prescribed dose with high precision strictly to the target and spares the surrounding tissues. Therefore, the risks of hypopituitarism, visual damage and vasculopathy are significantly lower. Furthermore, the latency of the radiation response after radiosurgery is substantially shorter than that of fractionated radiotherapy. The goal of this review is to define the efficacy, safety and role of radiosurgery for treatment of pituitary adenomas and to present the preliminary results of our institution.

Proton stereotactic radiotherapy for persistent adrenocorticotropin-producing adenomas

CONTEXT

Radiation therapy is a potentially curative treatment for corticotroph adenomas refractory to surgery. Protons have an advantage over photons (x-rays) by depositing energy at the target with no exit dose, providing a lower dose to adjacent normal tissues. Until recently, proton stereotactic radiotherapy (PSR) was available at only two U.S. centers; use will increase as proton facilities are under development.

OBJECTIVE

Our objective was to evaluate the efficacy and safety of PSR for persistent Cushing's disease (CD) and Nelson's syndrome (NS).

DESIGN

This was a retrospective review of 38 patients (33 with CD and five with NS) treated between 1992 and 2005.

PARTICIPANTS

All patients had transsphenoidal surgery without biochemical cure. Four had previous irradiation with photons. The patients with NS underwent bilateral adrenalectomy 29-228 months (median 40) before PSR.

INTERVENTION

Single-fraction PSR was delivered at a median dose of 20 Cobalt Gray Equivalents (range 15-20) on 1 treatment day.

MAIN OUTCOME MEASURES

Complete response (CR) was defined as sustained (> or =3 months) normalization of urinary free cortisol off medical therapy. CR in NS was based on normalization of plasma corticotropin.

RESULTS

At a median follow-up of 62 months (range 20-136), CR was achieved in five patients (100%) with NS and 17 (52%) patients with CD. Among all patients with CR, median time to CR was 18 months (range 5-49). No secondary tumors were noted on follow-up magnetic resonance imaging scans, and there was no clinical evidence of optic nerve damage, seizure, or brain injury. There were 17 patients (52%) who developed new pituitary deficits.

CONCLUSIONS

PSR is effective for patients with persistent corticotroph adenomas with low morbidity after a median follow-up of 62 months; longer follow-up is warranted for late radiation-related sequelae.

Radiotherapy and radiosurgery for Cushing's disease

Patients with residual or recurrent Cushing's disease receive external beam radiotherapy (RT) with the aim of achieving long-term tumour control and normalization of elevated hormone levels. Treatment is given either as conventional radiotherapy using conformal techniques or as stereotactic radiotherapy, which is either used as fractionated treatment (SCRT) or as single fraction radiosurgery (SRS). We describe the technical aspects of treatment and report a systematic review of the published literature on the efficacy and toxicity of conventional RT, SCRT and SRS. There are no studies directly comparing the different radiation techniques and the reported results are inevitably of selected patients by investigators with interest in the treatment tested. Nevertheless the review of the published literature suggests better hormone and tumour control rates after fractionated irradiation compared to single fraction radiosurgery. Hypopituitarism represents the most commonly reported late complication of radiotherapy seen after all treatments. Although the incidence of other late effects is low, the risk of radiation injury to normal neural structures is higher with single fraction compared to fractionated treatment. Stereotactic techniques offer more localized irradiation compared with conventional radiotherapy, however longer follow-up is necessary to confirm the potential reduction of long-term radiation toxicity of fractionated SCRT compared to conventional RT. On the basis of the available literature, fractionated conventional and stereotactic radiotherapy offer effective treatment for Cushing's disease not controlled with surgery alone. The lower efficacy and higher toxicity of single fraction treatment suggest that SRS is not the appropriate therapy for the majority of patients with Cushing's disease.

Radiotherapy of pituitary adenomas: state of the art

Pituitary adenomas represent approximately 12% of intracranial tumors. They are defined as tumors that are functional or nonfunctional and invasive or noninvasive. Therapeutic strategies rely on surgery, medical treatment, and radiotherapy depending on histology. Neither the role of external radiotherapy nor the technique to be used are firmly established. Nonfunctioning adenomas must be operated on to relieve the compression. Prolactin-secreting adenomas are first treated with dopamine agonists, and GH-secreting adenomas are first treated by surgery if excising the complete tumor is possible; otherwise medical treatment is started. The first-line treatment of ACTH-secreting adenomas is surgery; however, in many cases, insufficient control of either secretion or tumoral volume leads to consideration of irradiation. Complications of conventional radiotherapy are well known and fractionated stereotactic radiotherapy appears to be as safe as radiosurgery. The volume to irradiate is still difficult to define, and this parameter can influence the technique chosen for treatment. Because the indications of radiotherapy are still debated, irradiation of pituitary adenomas must be decided by the complete team of endocrinologists, neurosurgeons, radiologists and radiotherapists.

Pituitary adenomas treated with gamma knife radiosurgery: volumetric analysis of 100 cases with minimum 3 year follow-up

OBJECTIVE

To analyze pituitary adenoma volume changes after gamma knife radiosurgery (GKRS) in patients with 3 years of follow-up and to investigate factors that might affect these changes.

METHODS

Between January 1997 and March 2004, a total of 1930 patients were treated in the Gamma Knife Unit of the Marmara University Department of Neurosurgery in Istanbul, Turkey. Three hundred sixty of these patients had pituitary adenomas (PAs). This prospectively designed clinical study documents the radiological-volumetric analysis for the first 100 of these patients with PAs who had a minimum of 3 years of follow-up and met the study requirements. Each tumor was assessed with serial magnetic resonance imaging scans after radiosurgery; at each time point, adenoma volume was expressed as a percentage of the tumor's initial volume. Volume changes were investigated relative to margin dose, the cavernous sinus infiltration, and endocrinological type of adenoma.

RESULTS

At the end of the first year after GKRS, the PA volumes had decreased to approximately 90% of the initial volume on average. The corresponding approximate averages for the ends of Years 2 and 3 were 80 and 70% of the initial volume, respectively. At 3 years after GKRS, the PAs in the group with a peripheral dose of less than 17 Gy were reduced to approximately 80% of the initial volume on average. In contrast, the tumors in the patients with marginal doses of 21 to 23 Gy were reduced to approximately 60% of the initial volume at this stage. The adenomas treated with the highest marginal doses (>27 Gy) showed the earliest volume decreases after GKRS (6-9 mo after the procedure). Cavernous sinus noninfiltrating adenomas showed greater volume decreases after GKRS; on average, these masses were reduced to approximately 50% of their initial volume at 3 years. In contrast, the PAs that had infiltrated the cavernous sinus had only dropped to approximately 80% of their initial volume at this stage. The growth hormone-secreting PAs showed the maximum volume decrease with GKRS. On average, these lesions were approximately 60% of their initial volume at the 3-year stage. The nonfunctioning tumors and the prolactin-secreting adenomas showed similar volume changes over time. On average, these tumors had dropped to approximately 75 and 70% of the initial volume, respectively, by 3 years after GKRS.

CONCLUSION

Gamma knife radiosurgery halts the growth of pituitary adenomas. Cavernous sinus extension and margin dose are the most important determinants of adenoma volume after this type of therapy.

Gamma Knife surgery for Cushing's disease

Object

In this study the authors address the efficacy and safety of Gamma Knife surgery (GKS) in patients with adrenocorticotropic hormone–secreting pituitary adenomas.

Methods

A review of data collected from a prospective GKS database between January 1990 and March 2005 was performed in patients with Cushing's disease. All but one patient underwent resection for a pituitary tumor, without achieving remission. Successful endocrine outcome after GKS was defined as a normal 24-hour urinary free cortisol (UFC) concentration posttreatment after a minimum of 1 year of follow up. Patient records were also evaluated for changes in tumor volume, development of new hormone deficiencies, visual acuity, cranial nerve neuropathies, and radiation-induced imaging changes. Ninety evaluable patients had undergone GKS, with a mean endocrine follow-up duration of 45 months (range 12–132 months). The mean dose to the tumor margin was 23 Gy (median 25 Gy).

Normal 24-hour UFC levels were achieved in 49 patients (54%), with an average time of 13 months after treatment (range 2–67 months). In the 49 patients in whom a tumor was visible on the planning magnetic resonance (MR) image, a decrease in tumor size occurred in 39 (80%), in seven patients there was no change in size, and tumor growth occurred in three patients. Ten patients (20%) experienced a relapse of Cushing's disease after initial remission; the mean time to recurrence was 27 months (range 6–60 months). Seven of these patients underwent repeated GKS, with three patients achieving a second remission. New hormone deficiencies developed in 20 patients (22%), with hypothyroidism being the most common endocrinopathy after GKS. Five patients experienced new visual deficits or third, fourth, or sixth cranial nerve deficits; two of these patients had undergone prior conventional fractionated radiation therapy, and four of them had received previous GKS. Radiation-induced changes were observed on MR images in three patients; one had symptoms attributable to these changes.

Conclusions

Gamma Knife surgery is an effective treatment for persistent Cushing's disease. Adenomas with cavernous sinus invasion that are not amenable to resection are treatable with the Gamma Knife. A second GKS treatment appears to increase the risk of cranial nerve damage. These results demonstrate the value of combining two neurosurgical treatment modalities—microsurgical resection and GKS—in the management of pituitary adenomas.

Radiotherapy for nonfunctioning pituitary adenomas: from conventional to modern stereotactic radiation techniques

The initial management of nonfunctioning pituitary macroadenomas (NFAs) is usually surgery; however, a significant proportion of NFAs may require further treatment. Radiotherapy is currently used in patients with residual tumour and achieves excellent long-term control, but there are concerns about potential late toxicity. Stereotactic radiotherapy, both in the form of radiosurgery or fractionated stereotactic radiotherapy, has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. A review of the literature suggests that new radiation techniques offer safe and effective treatment for recurrent or residual pituitary adenomas; however longer follow-up is necessary to confirm the excellent tumour control and the potential reduction of long-term radiation toxicity. Currently, radiotherapy has an important role in patients with residual or progressive disease after surgery. Patients with small or no residual tumours after surgery may generally continue on a policy of surveillance without immediate irradiation, in order to avoid the potential toxicity of treatment.

Intensity-modulated radiotherapy for pituitary adenomas: The preliminary report of the Cleveland Clinic experience

PURPOSE

Intensity-modulated radiotherapy (IMRT) is being increasingly used for the treatment of pituitary adenomas. However, there have been few published data on the short- and long-term outcomes of this treatment. This is the initial report of the Cleveland Clinic's experience.

METHODS AND MATERIALS

Between February 1998 and December 2003, 34 patients with pituitary adenomas were treated with IMRT. A retrospective chart review was conducted for data analysis.

RESULTS

With a median follow-up of 42.5 months, the treatment has proven to be well tolerated, with performance status remaining stable in 90% of patients. Radiographic local control was 89%, and among patients with secretory tumors, 100% had a biochemical response. Only 1 patient required salvage surgery for progressive disease, giving a clinical progression free survival of 97%. The only patient who received more than 46 Gy experienced optic neuropathy 8 months after radiation. Smaller tumor volume significantly correlated with subjective improvements in nonvisual neurologic complaints (p = 0.03), and larger tumor volume significantly correlated with subjective worsening of visual symptoms (p = 0.05). New hormonal supplementation was required for 40% of patients. Younger patients were significantly more likely to require hormonal supplementation (p = 0.03).

CONCLUSIONS

Intensity-modulated radiation therapy is a safe and effective treatment for pituitary adenomas over the short term. Longer follow-up is necessary to determine if IMRT confers any advantage with respect to either tumor control or toxicity over conventional radiation modalities.

Linear accelerator radiosurgery for pituitary macroadenomas: a 7-year follow-up study

BACKGROUND

A prospective study was conducted to assess the efficacy and side effects of linear accelerator (LINAC)-based radiosurgery (RS) performed with a reduced dose of therapeutic radiation for patients with surgically inaccessible pituitary macroadenomas.

METHODS

From August 1990 through January 2004, 175 patients with pituitary macroadenomas were treated with LINAC-RS according to a prospective protocol. To minimize the risk for radiation-induced damage of the pituitary function, the therapeutic dose to be applied was limited to 20 grays.

RESULTS

Among 175 patients, 142 patients who had a minimum follow-up of 12 months (mean +/- standard deviation, 81.9 +/- 37.2 months) were included in the current study. The local tumor control rate was 96.5%, and the tumor response rate was 32.4%. The mean time (+/- standard deviation) from LINAC-RS to normalization of pathologic hormone secretion was 36.2 +/- 24.0 months. The probability for normalization was 34.3% at 3 years and 51.1% at 5 years. The frequency of endocrine cure (defined as the normalization of hormone secretion without specific medication intake) was 35.2% (mean +/- standard deviation time to cure, 42.1 +/- 25.0 months). Patients with Cushing disease had a statistically significant greater chance of achieving a cure (P = .001). Side effects of LINAC-RS were deterioration of anterior pituitary function (12.3%), radiation-induced tissue damage (2.8%), and radiation-induced neuropathy (1.4%).

CONCLUSIONS

LINAC-RS using a lower therapeutic radiation dose achieved local tumor control and normalization or cure of hormone secretion comparable to the results achieved with gamma-knife RS. Compared with the latter, the time to normalization or endocrine cure was delayed, most probably as a result of dose reduction. However, the lower therapeutic radiation dose did not prevent radiation-induced damage of pituitary function completely.

Gamma knife radiosurgery for medically and surgically refractory prolactinomas

OBJECTIVE

Experience with gamma knife radiosurgery (GKRS) for prolactinomas is limited because of the efficacy of medical and surgical intervention. Patients who are refractory to medical and/or surgical therapy may be treated with GKRS. We characterize the efficacy of GKRS for medically and surgically refractory prolactinomas.

METHODS

We reviewed our series of patients with prolactinomas who were treated with GKRS after failing medical and surgical intervention who had at least 1 year of follow-up.

RESULTS

Twenty-three patients were included in analysis of endocrine outcomes (median and average follow-up of 55 and 58 mo, respectively) and 28 patients were included in analysis of imaging outcomes (median and average follow-up of 48 and 52 mo, respectively). Twenty-six percent of patients achieved a normal serum prolactin (remission) with an average time of 24.5 months. Remission was significantly associated with being off of a dopamine agonist at the time of GKRS and a tumor volume less than 3.0 cm3 (P < 0.05 for both). Long-term image-based volumetric control was achieved in 89% of patients. Complications included new pituitary hormone deficiencies in 28% of patients and cranial nerve palsy in two patients (7%).

CONCLUSION

Clinical remission in 26% of treated patients is a modest result. However, because the GKRS treated tumors were refractory to other therapies and because complication rates were low, GKRS should be part of the armamentarium for treating refractory prolactinomas. Patients with tumors smaller than 3.0 cm3 and who are not receiving dopamine agonist at the time of treatment will likely benefit most.

Advances in the treatment of prolactinomas

Prolactinomas account for approximately 40% of all pituitary adenomas and are an important cause of hypogonadism and infertility. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism through the normalization of hyperprolactinemia and control of tumor mass. Medical therapy with dopamine agonists is highly effective in the majority of cases and represents the mainstay of therapy. Recent data indicating successful withdrawal of these agents in a subset of patients challenge the previously held concept that medical therapy is a lifelong requirement. Complicated situations, such as those encountered in resistance to dopamine agonists, pregnancy, and giant or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both. Progress in elucidating the mechanisms underlying the pathogenesis of prolactinomas may enable future development of novel molecular therapies for treatment-resistant cases. This review provides a critical analysis of the efficacy and safety of the various modes of therapy available for the treatment of patients with prolactinomas with an emphasis on challenging situations, a discussion of the data regarding withdrawal of medical therapy, and a foreshadowing of novel approaches to therapy that may become available in the future.

Gamma surgery in the treatment of nonsecretory pituitary macroadenoma

Object

The authors report on a retrospective analysis of the imaging and clinical outcomes following gamma surgery in 100 patients with nonsecretory pituitary macroadenoma.

Methods

Between June 1989 and March 2004, 100 consecutive patients with nonsecretory pituitary macroadenoma were treated at the Lars Leksell Center for Gamma Surgery, University of Virginia Health System (Charlottesville, VA). Ninety-two patients had residual or recurrent macroadenoma following one or more surgical procedures. In eight patients, gamma surgery was the primary treatment. Ten patients received conventional fractionated radiotherapy before the gamma surgery. Sixty-nine patients required hormone replacement therapy for one or more deficits before gamma knife treatment. Peripheral doses between 5 and 25 Gy (mean 18.5 Gy) were administered.

Imaging and endocrinological follow-up evaluations were performed in 90 patients; these studies ranged from 6 to 142 months (mean 44.9 months) and 6 to 127 months (mean 47.9 months), respectively. Tumor volume decreased in 59 patients (65.6%), remained unchanged in 24 (26.7%), and increased in seven (7.8%). The minimal effective peripheral dose was 12 Gy; peripheral doses greater than 20 Gy did not seem to provide additional benefit. Of 61 patients with a partially or fully functioning pituitary gland and follow-up data, 12 (19.7%) suffered new hormone deficits following gamma surgery. In patients with endocrinological follow-up data that had been collected over more than 2 years, the rate of new deficits was 25%. No neurological morbidity or death was related to treatment.

Conclusions

Current experience suggests that gamma surgery is an appropriate means of managing recurrent or residual nonsecretory pituitary macroadenoma following microsurgery and a primary treatment in selected patients. To evaluate definite rates of recurrence and new endocrine deficiencies, long-term follow-up studies are needed.

Gamma knife radiosurgery for acromegaly--long-term experience

OBJECTIVE

The Leksell gamma knife (LGK) is one of the treatment options for pituitary adenomas. We report on our long-term experience treating acromegaly using LGK.

DESIGN

Since 1993 we have followed 96 acromegaly patients through periods of from 12 to 120 months. The mean follow-up period was 53.7 +/- 26.8 months. Seventy-two patients were treated with neurosurgery prior to LGK; for 24 LGK was the primary treatment. Thirteen patients were irradiated twice, due to persistent activity of the adenoma or its residue. Pituitary functions were tested at 6-month intervals, post-irradiation. The target tumour volume for radiosurgery was between 93.3 and 12 700 mm3 (median 1350 mm3).

RESULTS

Fifty per cent of the patients achieved mean GH < 2.5 microg/l within 42 months, normalized their IGF-I within 54 months, and achieved GH suppression in the oral glucose tolerance test (oGTT) < 1 microg/l with normal IGF-I within 66 months. LGK effectiveness was dependent on initial adenoma hormonal activity (GH and IGF-I serum levels), not on the size of the adenoma. Patients with primary neurosurgery followed by LGK irradiation had better outcomes than those with LGK alone. Irradiation arrested all adenoma growth, causing tumour shrinkage in 62.3% of patients. Twenty-six developed hypopituitarism when irradiated by 15 Gy (or more) on functional peritumoral pituitary tissue. No hypopituitarism appeared using lower doses.

CONCLUSIONS

In acromegaly, LGK is a useful adjunct to primary neurosurgery when treating post-surgical residues because it can limit the duration of medical therapy. It can be used as a primary therapy when neurosurgery is not possible.

Treatment of pituitary adenomas by fractionated stereotactic radiotherapy: A prospective study of 110 patients

PURPOSE

To optimize and reduce the toxicity of pituitary adenoma irradiation by assessing the feasibility and effectiveness of fractionated stereotactic radiotherapy (FSR).

METHODS AND MATERIALS

Between 1990 and 1999, 110 consecutive patients, 47 with a functioning adenoma, were treated according to a strategy of either early surgery and FSR (n = 89) or FSR only (n = 21). Of the 110 patients, 75 had persistent macroscopic tumor and 47 persistent hormonal secretions; 15 were treated in the prophylactic setting. The linear accelerator-delivered dose was 50.4 Gy (5 x 1.8 Gy weekly), with a 2-mm safety margin.

RESULTS

After a minimal follow-up of 48 months, only 1 patient had developed progression. Of the 110 patients, 27 (36%) had a complete tumor response, 67 (89.3%) had an objective tumor response, 20 (42%) had a hormonal complete response, and 47 (100%) had a hormonal objective tumor response. The proportion of patients without a complete tumor response, objective tumor response, complete hormonal response, and objective hormonal response was 85.1%, 62%, 83%, and 59.3% at 4 years and 49.3%, 9%, 59.3%, and 10.6% at 8 years, respectively. The sole unfavorable predictive factor was preoperative SSE >20 mm for tumor response (p = 0.01) and growth hormone adenoma for the hormonal response (p <0.001). No late complications, except for pituitary deficiency, were reported, with a probability of requiring hormonal replacement of 28.5% and 35% at 4 and 8 years, respectively. Nonfunctioning status was the sole unfavorable factor (p = 0.0016).

CONCLUSIONS

Surgery plus FSR is safe and effective. FSR focused to the target volume seems more suitable than standard radiotherapy, and standard fractionation reduces the risk of optic neuropathy sometimes observed after single-dose radiosurgery. Therefore, FSR allows us to consider combined transrhinoseptal surgery and early radiotherapy, with a curative goal without patient selection.

Stereotactic radiosurgery for pituitary adenomas: an intermediate review of its safety, efficacy, and role in the neurosurgical treatment armamentarium

OBJECT

Pituitary adenomas are very common neoplasms, constituting between 10 and 20% of all primary brain tumors. Historically, the treatment armamentarium for pituitary adenomas has included medical management, microsurgery, and fractionated radiotherapy. More recently, radiosurgery has emerged as a viable treatment option. The goal of this research was to define more fully the efficacy, safety, and role of radiosurgery in the treatment of pituitary adenomas.

METHODS

Medical literature databases were searched for articles pertaining to pituitary adenomas and stereotactic radiosurgery. Each study was examined to determine the number of patients, radiosurgical parameters (for example, maximal dose and tumor margin dose), duration of follow-up review, tumor growth control rate, complications, and rate of hormone normalization in the case of functioning adenomas. A total of 35 peer-reviewed studies involving 1621 patients were examined. Radiosurgery resulted in the control of tumor size in approximately 90% of treated patients. The reported rates of hormone normalization for functioning adenomas varied substantially. This was due in part to widespread differences in endocrinological criteria used for the postradiosurgical assessment. The risks of hypopituitarism, radiation-induced neoplasia, and cerebral vasculopathy associated with radiosurgery appeared lower than those for fractionated radiation therapy. Nevertheless, further observation will be required to understand the true probabilities. The incidence of other serious complications following radiosurgery was quite low.

CONCLUSIONS

Although microsurgery remains the primary treatment modality in most cases, stereotactic radiosurgery offers both safe and effective treatment for recurrent or residual pituitary adenomas. In rare instances, radiosurgery may be the best initial treatment for patients with pituitary adenomas. Further refinements in the radiosurgical technique will likely lead to improved outcomes.

The efficacy of linear accelerator radiosurgery in the management of patients with Cushing's disease

We identified 35 patients who had undergone stereotactic radiosurgery (SRS) for their biochemically proven Cushing's disease in order to assess the efficacy of SRS with regard to control of hypercortisolism, improvement of clinical features and prevention of tumor progression, and subsequent incidence of hypopituitarism. Seventeen (49%) patients achieved control of their cortisol levels following SRS; the mean time to normalization was 7.5 months (range: 1-33). Four (19%) patients experienced recurrent hypercortisolism at a mean time of 35.5 months following therapy (range: 17-64). Control of tumor progression was achieved in 91% patients. Fourteen (40%) patients demonstrated a new pituitary deficiency following SRS. Our results suggest that cortisol levels are normalized more efficiently and with a lower recurrence rate with SRS than with conventional fractionated external beam radiotherapy (EBT). We have confirmed the near 100% tumor control rate reported with SRS. The percentage of patients developing pituitary insufficiency following SRS is less than that of patients having undergone EBT; however, deficits occurred up to 10 years posttreatment. We advocate the use of SRS as the primary therapeutic modality in those patients who are poor surgical candidates, or as the adjunct treatment to microsurgery in eliminating residual tumor cells or disease that is not easily amenable to resection.

Gamma knife radiosurgery for nonfunctioning pituitary adenomas

The efficacy of gamma knife radiosurgery (GKS) for non-functioning pituitary adenomas (NPAs) has been assessed. Sixty patients with NPA were treated by GKS. Complete neurological and endocrinological follow-up information was available for 51 patients. Follow-up examinations included stereotactic magnetic resonance imaging for sequential measurements of the NPA volume. The median dose to the tumor margin was 16.5 Gy (range 11-20 Gy). The mean prescription isodose was 50% (range 45-75%). All patients underwent surgery for NPA before GKS. Fractionated radiotherapy was not applied. Median follow up after GKS was 21,7 months. Actuarial recurrence-free survival was 95% after three years with respect to a single GKS and 100% for patients who underwent repeated GKS. No neurological side effects were detected. Two patients developed new partial pituitary insufficiency after radiosurgery. Postoperative GKS for residual or recurrent small fragments of NPAs is an effective and safe treatment option. The follow-up examination for NPAs should include tumor volumetric analysis.

Gamma knife radiosurgery in neuro-ophthalmology

PURPOSE OF REVIEW

Following technological advances in imaging and dose planning made in the past decade, gamma knife radiosurgery has become more and more an established treatment for a wide range of indications of interest and import to the neuro-ophthalmology community. These areas include cavernous sinus lesions and sellar lesions (for which radiosurgery can be offered as adjuvant or in certain cases as primary treatment), cavernous sinus fistulae, parasellar syndromes, and pituitary tumors.

RECENT FINDINGS

Occurrence of radiation-induced cranial nerve deficits and radiation-induced optic neuropathy are infrequent following radiosurgery to these areas, and perhaps radiation-induced necrosis is less prevalent than in conventional radio therapeutic interventions.

SUMMARY

Gamma knife radiosurgery remains a compelling treatment for lesions of the cavernous sinus, pineal, and sellar regions and offers increasing applicability for ocular conditions such as uveal melanoma and glaucoma.