Stereotactic conformal radiotherapy for pituitary adenomas: technique and preliminary experience

Consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence: Part 1, general recommendations

Tumours of the anterior part of the pituitary gland represent just 1% of all childhood (aged <15 years) intracranial neoplasms, yet they can confer high morbidity and little evidence and guidance is in place for their management. Between 2014 and 2022, a multidisciplinary expert group systematically developed the first comprehensive clinical practice consensus guideline for children and young people under the age 19 years (hereafter referred to as CYP) presenting with a suspected pituitary adenoma to inform specialist care and improve health outcomes. Through robust literature searches and a Delphi consensus exercise with an international Delphi consensus panel of experts, the available scientific evidence and expert opinions were consolidated into 74 recommendations. Part 1 of this consensus guideline includes 17 pragmatic management recommendations related to clinical care, neuroimaging, visual assessment, histopathology, genetics, pituitary surgery and radiotherapy. While in many aspects the care for CYP is similar to that of adults, key differences exist, particularly in aetiology and presentation. CYP with suspected pituitary adenomas require careful clinical examination, appropriate hormonal work-up, dedicated pituitary imaging and visual assessment. Consideration should be given to the potential for syndromic disease and genetic assessment. Multidisciplinary discussion at both the local and national levels can be key for management. Surgery should be performed in specialist centres. The collection of outcome data on novel modalities of medical treatment, surgical intervention and radiotherapy is essential for optimal future treatment.

Long-term outcomes of acromegaly treated with fractionated stereotactic radiation: case series and literature review

Background

Growth hormone (GH)-secreting pituitary adenomas represent an uncommon subset of pituitary neoplasms. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) have been used as primary or adjuvant treatment. The purpose of this study is to report the long-term tumor control and toxicity from our institution and to perform a systematic literature review of acromegaly patients treated with FSRT.

Methods

We retrospectively reviewed all patients treated with FSRT (median dose 50.4 Gray [Gy], range 50.4-54 Gy) between 2005 and 2012 who had: 1) GH-secreting adenoma with persistently elevated insulin growth factor-1 (IGF-1) despite medical therapy and 2) clinical follow up >3 years after FSRT. Patients were treated with modern FSRT planning techniques. Biochemical control was defined as IGF-1 normalization. Systematic review of the literature was performed for FSRT in acromegaly.

Results

With a median follow-up of 80 months, radiographic control was achieved in all 11 patients and overall survival was 100%. Long-term biochemical control was achieved in 10 patients (90.9%) with either FSRT alone (36.4%) or FSRT with continued medical management (45.5%). No patient experienced new hypopituitarism, cranial nerve dysfunctions, or visual deficits. Our systematic review found published rates of biochemical control and hypopituitarism vary, with uniformly good radiographic control and low incidence of visual changes.

Conclusions

Adjuvant FSRT offered effective long-term biochemical control and radiographic control, and there was a lower rate of complications in this current series. Review of the literature shows variations in published rates of biochemical control after FSRT for acromegaly, but low incidence of serious toxicities.

Risk-adapted single or fractionated stereotactic high-precision radiotherapy in a pooled series of nonfunctioning pituitary adenomas: high local control and low toxicity

PURPOSE

The purpose of this work was to evaluate a prospectively initiated two-center protocol of risk-adapted single-fraction (SRS) or fractionated radiotherapy (SRT) in patients with nonsecretory pituitary adenomas (NSA).

PATIENTS AND METHODS

A total of 73 NSA patients (39 men/34 women) with a median age of 62 years were prospectively included in a treatment protocol of SRS [planning target volume (PTV) < 4 ccm, > 2 mm to optic pathways = low risk] or SRT (PTV ≥ 4 ccm, ≤ 2 mm to optic pathways = high risk) in two Novalis® centers. Mean tumor volume was 7.02 ccm (range 0.58-57.29 ccm). Based on the protocol guidelines, 5 patients were treated with SRS and 68 patients with SRT.

RESULTS

Median follow-up (FU) reached 5 years with 5-year overall survival (OS) of 90.4 % (CI 80.2-95 %) and 5-year local control and progression-free survival rates of 100 % (CI 93.3-100 %) and 90.4 % (CI 80.2-95 %), respectively. A post-SRS/SRT new visual disorder occurred in 2 patients (2.7 %), a new oculomotor nerve palsy in one pre-irradiated patient, in 3 patients (4.1 %) a pre-existing visual disorder improved. New complete hypopituitarism occurred in 4 patients (13.8 %) and in 3 patients (25 %) with pre-existing partial hypopituitarism. Pituitary function in 26 % of patients retained normal. Patients with tumor shrinkage (65.75 %) had a significantly longer FU (p = 0.0093). Multivariate analysis confirmed correlation of new hypopituitarism with duration of FU (p = 0.008) and correlation of new hypopituitarism and tumor volume (p = 0.023). No significant influence factors for occurrence of visual disorders were found.

CONCLUSION

Our SRS/SRT protocol proved to be safe and successful in terms of tumor control and protection of the visual system, especially for large tumors located close to optic pathways.

Visual outcome after fractionated stereotactic radiation therapy of benign anterior skull base tumors

To determine visual outcome including the occurrence of radiation induced optic neuropathy (RION) as well as tumor control after fractionated stereotactic radiation therapy (FSRT) of benign anterior skull base meningiomas or pituitary adenomas. Thirty-nine patients treated with FSRT for anterior skull base meningiomas and 55 patients treated with FSRT for pituitary adenomas between January 1999 and December 2009 with at least 2 years follow-up were included. Patients were followed up prospectively with magnetic resonance imaging scans, visual acuity and visual field examinations. RION was found in four (10%) patients with anterior skull base meningiomas and seven patients (13%) with pituitary adenomas. The five-year actuarial freedom from 25% RION visual field loss was 94% following FSRT. Actuarial 2-, 5- and 10-year tumor control rates were 100, 88.4 and 64.5% for anterior skull base meningiomas and 100, 98.2 and 94.9% for pituitary adenomas, respectively. Patients with an impaired visual field function pre-FSRT were more likely to experience worsened function (p = 0.016). We found that RION, was a relatively uncommon event, in a large prospective cohort of patients that were systematically monitored following FSRT of benign anterior skull base tumors. Long term tumor control was favorable, especially for pituitary adenomas.

HYPOFRACTIONATED CYBERKNIFE RADIOSURGERY FOR PERICHIASMATIC PITUITARY ADENOMAS

OBJECTIVE

Radiation therapy is recommended for pituitary tumors that are refractory to surgical and medical therapies. The efficacy of single-fraction radiosurgery is established for these lesions, but lesions within 3 mm of the optic pathway cannot be safely treated with doses higher than 8 to 10 Gy. We hypothesized that the optic nerve will tolerate 5 consecutive daily radiosurgery fractions of 500 cGy with effective tumor control.

METHODS

We reviewed our first 20 patients with recurrent or residual pituitary adenomas within 3 mm of the optic chiasm treated with the CyberKnife radiosurgery system (Accuray, Inc., Sunnyvale, CA). Tumors were treated with a mean coverage of 97 ± 2.2% (range, 89.8–99.7%), a mean conformity index of 1.3 ± 0.2 (range, 1.1–1.6), and a mean treatment isodose line of 74.5 ± 6.6% (range, 60–86%). The primary end point was an interim analysis of visual preservation, and secondary end points were radiographic and endocrinological tumor control.

RESULTS

The mean follow-up period for visual field testing was 26.6 ± 10.5 months (range, 10.6–41 months). The vision of all 14 patients with intact preoperative vision remained intact. Of the 5 patients with impaired vision, 2 remained stable, and 3 improved. No patient's vision deteriorated. The mean radiographic follow-up was 29.3 ± 8.6 months (range, 10.2–40.5 months). On magnetic resonance imaging, 12 tumors were stable, 8 were smaller, and none enlarged.

CONCLUSION

This preliminary study establishes that the optic nerve and chiasm tolerate CyberKnife hypofractionated radiosurgery of 5 × 500 cGy to perichiasmatic pituitary adenomas. Early data suggest that this dosing paradigm may achieve satisfactory radiographic and endocrinological tumor control for these challenging lesions, but longer follow-up is necessary to confirm these results.

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.

Gamma knife radiosurgery is a successful adjunctive treatment in Cushing's disease

OBJECTIVE

Though transsphenoidal surgery remains the first-line treatment of Cushing's disease, recurrence occurs frequently. Conventional radiotherapy and anticortisolic drugs both have adverse effects. Stereotactic radiosurgery needs to be evaluated more precisely. The aim of this study was to determine long-term hormonal effects and tolerance of gamma knife (GK) radiosurgery in Cushing's disease.

DESIGN

Forty patients with Cushing's disease treated by GK were prospectively studied over a decade, with a mean follow-up of 54.7 months. Eleven of them were treated with GK as a primary treatment.

METHODS

Radiosurgery was performed at the Department of Functional Neurosurgery of Marseille, France, using the Leksell Gamma Unit B and C models. Median margin dose was 29.5 Gy. Patients were considered in remission if they had normalized 24-h free urinary cortisol and suppression of plasma cortisol after low-dose dexamethasone suppression test.

RESULTS

Seventeen patients (42.5%) were in remission after a mean of 22 months (range 12-48 months). The two groups did not differ in terms of initial hormonal levels. Target volume was significantly higher in uncured than in remission group (909.8 vs 443 mm(3), P = 0.038). We found a significant difference between patients who were on or off anticortisolic drugs at the time of GK (20 vs 48% patients in remission respectively, P = 0.02).

CONCLUSION

With 42% of patients in remission after a median follow-up of 54 months, GK stereotactic radiosurgery, especially as an adjunctive treatment to surgery, may represent an alternative to other therapeutic options in view of their adverse effects.

Fractionated stereotactic conformal radiotherapy for secreting and nonsecreting pituitary adenomas

OBJECTIVE

To assess the medium-term outcome in a cohort of patients with residual or recurrent pituitary adenoma treated with fractionated stereotactic conformal radiotherapy (SCRT).

PATIENTS AND METHODS

Ninety-two patients (median age 50 years) with a residual or recurrent nonfunctioning (67) or a secreting (25) pituitary adenoma were treated between 1995 and 2003. Eighteen patients had a GH-secreting, five PRL-secreting and two an ACTH-secreting pituitary adenoma. Vision was impaired in 39 patients, with visual field deficit (35) and/or reduced visual acuity (25). Sixty-four patients had partial or complete hypopituitarism before SCRT. The treatment was delivered stereotactically by four noncoplanar conformal fixed fields using a 6-MV linear accelerator to a dose of 45 Gy in 25 fractions.

RESULTS

At a median follow-up of 32 months (range 4-108) the 1, 3 and 5 years actuarial progression-free survival is 99%, 98% and 98%, and overall survival is 98%. Three patients recurred 5 months, 1 year and 9 years after SCRT requiring surgery. In secreting adenomas, hormone levels declined progressively, becoming normal in more than a third of patients with GH-secreting and PRL-secreting pituitary tumours. 50% of baseline GH level was achieved in just under 2 years. The treatment was well tolerated with minimal acute toxicity. Hypopituitarism was the most common long-term effect; 22% of patients had worsening of pituitary function. One patient developed unilateral quadrantopia without tumour progression.

CONCLUSION

SCRT as a high-precision technique of localized irradiation achieves tumour and hormone control of pituitary adenomas comparable with previously published data on the efficacy of conventional radiotherapy. Despite the potential advantage of reducing the volume of normal brain irradiated, the theoretical benefit over conventional radiotherapy in terms of the reduction in long-term morbidity has not yet been demonstrated and requires longer follow-up. Potential effect on long-term cognitive function has not been tested.

Role of radiotherapy in the management of acromegaly

Active acromegaly can be treated effectively by transsphenoidal surgery, radiotherapy and medical treatment in the form of somatostatin analogs and growth hormone receptor antagonists. Many patients will require a combination of treatment modalities to normalize growth hormone excess and associated increased mortality, and to improve comorbidity. Following postoperative radiotherapy, growth hormone and insulin-like growth factor-I levels gradually decrease and normalization of growth hormone and insulin-like growth factor-I is achieved in 50% of patients after 5 years and 75% after 10 years. Disadvantages of radiotherapy include the long interval until hormone levels have sufficiently decreased and the high incidence of radiation-induced hypopituitarism. Radiotherapy was associated with increased mortality in some but not other studies. Limitations in the design and confounding factors, such as years spent with active disease and changing treatment strategies, make it impossible to draw conclusions on this topic. Gamma knife radiosurgery may combine faster decline of growth hormone excess with a lower incidence of hypopituitarism in eligible cases, but long-term results of this radiation technique are lacking. At present, patients will preferentially be treated by primary surgery and/or somatostatin analog treatment, followed, if necessary, by growth hormone receptor antagonist treatment, while radiotherapy is reserved for selected cases only. The indications for radiotherapy and radiosurgery need to be revisited in the near future, when longer follow-up results for medical treatment and radiosurgery have become available. This review summarizes the recent literature on efficacy and side effects of radiotherapy and radiosurgery in acromegaly and discusses the place of radiation treatment in the treatment algorithm of acromegaly.

Experience of external beam radiotherapy given adjuvantly or at relapse following surgery for craniopharyngioma

BACKGROUND AND PURPOSE

Evaluation of effect of timing of external beam radiation therapy (EBRT) following surgery for craniopharyngioma.

MATERIALS AND METHODS

Between 1976 and 2002, 87 patients (28 children) received EBRT in a regional referral centre. Forty-four patients received EBRT adjuvantly and 43 on relapse. The median total dose was 42.5Gy (range 34.7-52.5Gy) in 2.25-2.83Gy fractions over a median of 20 days (range 17-32). Effect of EBRT timing, type of original surgery, age on survival, progression-free survival (PFS) and quality of life (QOL) was studied.

RESULTS

Survival from diagnosis was 86 and 76% and PFS was 78 and 66% at 10 and 20 years, respectively, with no significant difference seen between those treated adjuvantly or at relapse or according to age. QOL deteriorated significantly from diagnosis to last follow-up. Excluding patients who relapsed following EBRT, QOL did not deteriorate significantly overall (P=0.35). Children had worse QOL and greater morbidity at all timepoints compared to adults.

CONCLUSIONS

EBRT is effective both adjuvantly and at relapse. QOL deteriorates over time-relapse following EBRT was the only significant factor. Children have greater morbidity compared to adults, but no evidence for greater EBRT-induced toxicity was seen.

Cerebrovascular disease in patients with pituitary tumors

Several studies have shown that patients with acromegaly have increased mortality rates for cardiovascular disease and cerebrovascular disease (CVD). Similar associations have also been seen for patients with hypopituitarism or with non-functional pituitary adenomas. This review summarizes these data and discusses the relative importance of different risk factors for cardiovascular, especially CVD, mortality among patients with acromegaly or non-functional pituitary adenomas, and for those with hypopituitarism as a result of other causes.

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.

Integration of surgery with fractionated stereotactic radiotherapy for treatment of nonfunctioning pituitary macroadenomas

OBJECTIVE

To evaluate the efficacy of fractionated stereotactic radiotherapy (FSRT) after surgery in the management of residual or recurrent nonfunctioning pituitary adenomas with respect to tumor control and the development of complications.

METHODS AND MATERIALS

The clinical records of patients with nonfunctioning pituitary adenomas who underwent FSRT were retrospectively analyzed. For newly diagnosed tumors, transsphenoidal surgery was performed, and, if residual tumor was identified at 3 months, FSRT was performed. If significant tumor volume persisted, transcranial surgery was performed before FSRT. We originally initiated FSRT with 2-Gy fractions to 46 Gy. We escalated the dose to 50.4 Gy thereafter. As a final modification, we dropped the daily dose to 1.8-Gy fractions delivered within 6 weeks. High-dose conformality and homogeneity was achieved with arc beam shaping and differential beam weighting. The radiographic, endocrinologic, and visual outcomes after FSRT were evaluated.

RESULTS

The 68 patients included 36 males and 32 females with an age range of 15-81 years. The median follow-up was 30 months (range, 2-82 months), and the median tumor volume was 6.2 cm(3). Of the 68 patients, 20 were treated to 46 Gy and 48 to 50-52.2 Gy. Most were treated to 50.4 Gy. Eleven patients had recurrent tumors, 54 had residual tumors, and no surgery was performed in 3 patients before FSRT. We noted no radiation-induced acute or late toxicities, except for radiation-induced optic neuropathy in 2 patients. At latest follow-up, the tumor had decreased in size in 26 patients and remained stable in 41 of the 42 remaining patients. Of the 68 patients, 4 (6%) developed hypopituitarism at 6, 11, 12, and 17 months after FSRT. Reviewing available serial Humphrey visual fields, visual fields were objectively improved in 28 patients, and remained stable in 24 patients, and worsened in 2 patients.

CONCLUSION

The findings of this analysis support the use of surgery followed by FSRT as a safe, effective, and integrated treatment for nonfunctioning pituitary adenomas. Additional follow-up is needed to document the long-term tumor control rates, preservation rates for vision and pituitary function, and neurocognitive outcomes.

The long-term efficacy of conventional radiotherapy in patients with GH-secreting pituitary adenomas

OBJECTIVE

To assess the long-term efficacy and safety of conventional radiotherapy (RT) in the control of acromegaly according to recent stringent criteria of cure.

DESIGN

A retrospective longitudinal study.

PATIENTS AND METHODS

Forty-seven patients with active acromegaly were treated with conventional RT between 1982 and 1994. All patients were first operated on and successively irradiated at a dose of 45-50 Gy in 25-28 fractions for persistent (n = 40) or recurrent (n = 7) disease.

MEASUREMENTS

Long-term GH/IGF-I secretion and local tumour control were evaluated regularly, and possible side-effects were searched for systematically, especially in terms of secondary endocrine dysfunction. Biochemical cure of acromegaly was defined by glucose-suppressed plasma GH levels below 1 microg/l during an oral glucose tolerance test (OGTT) and normal age-corrected IGF-I values.

RESULTS

The 5-, 10- and 15-year overall survival rates were 98%, 95% and 93%, respectively. Suppression of GH during OGTT was seen in 9% of patients at 2 years, 29% at 5 years, 52% at 10 years, and 77% at 15 years. Age-corrected IGF-I levels were normal in 8% of patients 2 years after RT, and this proportion increased to 23%, 42% and 61% after 5, 10 and 15 years, respectively. Normalization of GH/IGF-I mainly depended on pre-RT levels. Local tumour control was 95% at 5, 10 and 15 years after treatment. Late toxicity was mainly represented by progressive hypopituitarism, which was present in 33% of patients at baseline and increased to 57%, 78% and in 85% of patients at 5 10 and 15 years after RT, respectively.

CONCLUSION

Conventional RT is effective in the long-term control of GH-secreting pituitary adenomas, although with a high prevalence of progressive hypopituitarism. At present, it remains a suitable option in acromegalic patients uncontrolled by surgery or medical therapy.

Prolactinomas and pregnancy

Prolactinomas are the most frequent pituitary tumors. Treatment of infertility in such tumors usually is very successful. On the other hand, reports of pituitary tumor growth during pregnancy have been described since bromocriptine started to be used. Since then, dopamine agonists (DA) have been increasingly used as the first-choice treatment of prolactinomas, with surgery being reserved for resistance or persistent intolerance to DA or for special situations. More recently other DA, such as quinagolide and cabergoline have shown better tolerance than bromocriptine with similar or greater efficacy. Cabergoline is now the first choice drug but its use in pregnancy is still under evaluation. We followed 71 term pregnancies in women bearing microprolactinomas. Of the 22 patients with previous surgery, none presented symptoms of tumor growth. Of the 41 pregnant patients treated with bromocriptine alone, only one (2.4%) presented with headaches, which regressed with drug reintroduction. Fifty one term pregnancies in patients with macroprolactinomas were followed by us. Of those, 21 were in patients with previous surgery and none of them presented clinical evidence of tumor growth. On the other hand, of the 30 patients treated only with pre-gestational bromocriptine, 11 (37%) manifested complaints related to tumor growth. A non-hormonal contraceptive should be the use along with a DA drug until tumor shrinkage within sellar boundaries has been evidenced. After pregnancy has been confirmed, the DA can be withdrawn and the patient must be closely followed. If tumor expansion is suspected, confirmation can be made through MRI and by visual field testing. Reintroduction of bromocriptine in such cases can lead to tumor reduction and clinical improvement. Surgery can also be employed as treatment for symptomatic tumor growth in pregnancy.

Treatment accuracy of fractionated stereotactic radiotherapy

BACKGROUND AND PURPOSE

To assess the geometric accuracy of the delivery of fractionated stereotactic radiotherapy (FSRT) for brain tumours using the Gill-Thomas-Cosman (GTC) relocatable frame. Accuracy of treatment delivery was measured via portal images acquired with an amorphous silicon based electronic portal imager (EPI). Results were used to assess the existing verification process and to review the current margins used for the expansion of clinical target volume (CTV) to planning target volume (PTV).

PATIENTS AND METHODS

Patients were immobilized in a GTC frame. Target volume definition was performed on localization CT and MRI scans and a CTV to PTV margin of 5mm (based on initial experience) was introduced in 3D. A Brown-Roberts-Wells (BRW) fiducial system was used for stereotactic coordinate definition. The existing verification process consisted of an intercomparison of the coordinates of the isocentres and anatomy between the localization and verification CT scans. Treatment was delivered with 6 MV photons using four fixed non-coplanar conformal fields using a multi-leaf collimator. Portal imaging verification consisted of the acquisition of orthogonal images centred through the treatment isocentre. Digitally reconstructed radiographs (DRRs) created from the CT localization scans were used as reference images. Semi-automated matching software was used to quantify set up deviations (displacements and rotations) between reference and portal images.

RESULTS

One hundred and twenty six anterior and 123 lateral portal images were available for analysis for set up deviations. For displacements, the total errors in the cranial/caudal direction were shown to have the largest SD's of 1.2 mm, while systematic and random errors reached SD's of 1.0 and 0.7 mm, respectively, in the cranial/caudal direction. The corresponding data for rotational errors (the largest deviation was found in the sagittal plane) was 0.7 degrees SD (total error), 0.5 degrees (systematic) and 0.5 degrees (random). The total 3D displacement was 1.8 mm (mean), 0.8 mm (SD) with a range of 0.3-3.9 mm.

CONCLUSIONS

Portal imaging has shown that the existing verification and treatment delivery techniques currently in use result in highly reproducible setups. Random and systematic errors in the treatment planning and delivery chain will always occur, but monitoring and minimising them is an essential component of quality control. Portal imaging provides fast and accurate facility for monitoring patients on treatment and the results of this study have shown that a reduction in CTV to PTV margin from 5 to 4 mm (resulting in a considerable increase in the volume of normal tissue sparing) could be made.

Stereotactic Linear Accelerator Radiotherapy for Pituitary Tumors

Last decade has seen important advances in radiotherapy technology which combine precise tumor localization with accurate targeted delivery of radiation. This technique of high precision conformal radiotherapy, described as stereotactic radiotherapy or radiosurgery, uses modern linear accelerators available in most radiation oncology departments. The article describes the new technique as applied to the treatment of pituitary adenoma and reviews published clinical results.

Diagnóstico e tratamento da acromegalia no Brasil

Acromegalia é uma doença debilitante e desfigurante que, se não controlada adequadamente, reduz a expectativa de vida do paciente. Complicações cardiovasculares e respiratórias representam as principais causas de morte nos acromegálicos. Atualmente, o diagnóstico é realizado de acordo com as diretrizes do consenso de 2000: ausência de supressão do GH para um valor <1ng/mL e IGF-1 elevado. Avanços em todas as modalidades terapêuticas têm ocorrido, propiciando o controle bioquímico da doença em um número cada vez maior de pacientes. Estudos prévios mostraram que a obtenção de níveis seguros de GH (GH médio <2,5ng/mL) e de IGF-1 normal reduz a taxa de mortalidade para o normal. Em 2002, foram publicadas diretrizes para o manejo da acromegalia, o qual envolve, muitas vezes, uma abordagem multidisciplinar. Neste artigo, fazemos uma avaliação crítica do que dispomos no Brasil para seguirmos as diretrizes estabelecidas nos consensos sobre diagnóstico e tratamento da acromegalia.

Gamma-knife radiosurgery in acromegaly: a 4-year follow-up study

Stereotactic radiosurgery by gamma-knife (GK) is an attractive therapeutic option after failure of microsurgical removal in patients with pituitary adenoma. In these tumors or remnants of them, it aims to obtain the arrest of cell proliferation and hormone hypersecretion using a single precise high dose of ionizing radiation, sparing surrounding structures. The long-term efficacy and toxicity of GK in acromegaly are only partially known. Thirty acromegalic patients (14 women and 16 men) entered a prospective study of GK treatment. Most were surgical failures, whereas in 3 GK was the primary treatment. Imaging of the adenoma and target coordinates identification were obtained by high resolution magnetic resonance imaging. All patients were treated with multiple isocenters (mean, 8; range, 3-11). The 50% isodose was used in 27 patients (90%). The mean margin dose was 20 Gy (range, 15-35), and the dose to the visual pathways was always less than 8 Gy. After a median follow-up of 46 months (range, 9-96), IGF-I fell from 805 micro g/liter (median; interquartile range, 640-994) to 460 micro g/liter (interquartile range, 217-654; P = 0.0002), and normal age-matched IGF-I levels were reached in 7 patients (23%). Mean GH levels decreased from 10 micro g/liter (interquartile range, 6.4-15) to 2.9 micro g/liter (interquartile range, 2-5.3; P < 0.0001), reaching levels below 2.5 micro g/liter in 11 (37%). The rate of persistently pathological hormonal levels was still 70% at 5 yr by Kaplan-Meier analysis. The median volume was 1.43 ml (range, 0.20-3.7). Tumor shrinkage (at least 25% of basal volume) occurred after 24 months (range, 12-36) in 11 of 19 patients (58% of assessable patients). The rate of shrinkage was 79% at 4 yr. In no case was further growth observed. Only 1 patient complained of side-effects (severe headache and nausea immediately after the procedure, with full recovery in a few days with steroid therapy). Anterior pituitary failures were observed in 2 patients, who already had partial hypopituitarism, after 2 and 6 yr, respectively. No patient developed visual deficits. GK is a valid adjunctive tool in the management of acromegaly that controls GH/IGF-I hypersecretion and tumor growth, with shrinkage of adenoma and no recurrence of the disease in the considered observation period and with low acute and chronic toxicity.

Stereotactic conformal radiotherapy for posterior fossa tumours: a modelling study for potential improvement in therapeutic ratio

PURPOSE

To investigate the optimal technique of stereotactic conformal radiotherapy (SCRT) for posterior fossa tumours.

MATERIAL AND METHODS

SCRT planning image data sets of four patients with posterior fossa tumours constituted the study material. Based on the operative notes and preoperative imaging, a clinical target volume (CTV) was drawn for each patient. An additional CTV representative of a typical posterior fossa tumour was also drawn on each patient's localisation scans. Therefore a total of eight CTVs differing in their size and location were used for further work. A margin of 5 mm was grown in three dimensions to result in a final planning target volume (PTV). Beam arrangements studied were conformal bilateral parallel pair, a three-field coplanar arrangement with two bilateral and a vertex beam, two three-field non-coplanar techniques and a six-field non-coplanar technique with conformation achieved by micromultileaf collimator (mMLC). Normal structures contoured included normal posterior fossa brain (excluding PTV), brain stem, cochleae, optic apparatus, pituitary-hypothalamic axis (PHA), supratentorial brain and the temporal lobes. Comparative evaluation of plans was done with dose volume histograms (DVH), conformity index (CI) and dose heterogeneity (DH).

RESULTS

In all plans, the 95% isodose line covered at least 99% of the PTV with acceptable dose heterogeneity. As compared to the baseline bilateral conformal parallel pair plan, all other plans achieved significantly more sparing of the normal posterior fossa brain at the 95 and 80% dose prescription levels with superior CI (at 95% isodose). The six-field technique resulted in maximum sparing as compared to the bilateral plan with a mean additional sparing of 74% (46.2 cm3) and 55% (33.83) at 95 and 80% dose prescription level, respectively (P<0.0001). Among the three field plans, the technique of bilateral and vertex fields resulted in least doses to cochlea and also irradiated the least volume of brain stem and PHA. Comparison of this technique to the six-field technique did not show any significant difference in sparing of normal structures in the posteriorly placed tumours. In anteriorly placed tumours, the six-field technique was the most optimal irrespective of the size of the target volumes.

CONCLUSIONS

A six-field plan SCRT achieves the most significant sparing of the normal tissues for localised irradiation in posterior fossa tumours, particularly for anteriorly located tumours. A relatively simpler three-field plan with bilateral and a vertex beam is equally good for tumours that are placed posteriorly and away from the brain stem.

Pituitary Adenomas

Treatment of pituitary adenomas can be pharmacologic or surgical. First- line treatment of prolactinomas is usually medical, using either bromocriptine or cabergoline. Other symptomatic pituitary adenomas typically should be treated with transsphenoidal surgery. Radiation therapy can be adjunctive for residual or recurrent tumor. The prognosis for endocrinologic and visual improvement is usually good.

Fractionated stereotactic radiotherapy: a short review

Currently, optimally precise delivery of intracranial radiotherapy is possible with stereotactic radiosurgery and fractionated stereotactic radiotherapy. We present in this article a review of the underlying basic physical and radiobiological principles of fractionated stereotactic radiotherapy and review the clinical experience for ateriovenus malformations, pituitary adenomas, mengiomas, vestibular schwanomas, low grade astrocytomas, malignant gliomas, and brain metastases.

High precision focused irradiation in the form of fractionated stereotactic conformal radiotherapy (SCRT) for benign meningiomas predominantly in the skull base location

OBJECTIVE

To present early clinical results of stereotactic conformal radiotherapy (SCRT) in patients with benign predominantly skull base meningiomas.

MATERIAL AND METHODS

Between August 1994 and August 1999, 41 patients with benign residual or recurrent meningiomas were treated with SCRT. Thirty-three were histologically verified. All patients were immobilized in a GTC stereotactic relocatable frame, and underwent a post-contrast CT localization scan with additional MRI for fusion in 15 patients. Treatment was delivered on a 6 MV linear accelerator using three (12 patients), or 4 (29 patients) non-coplanar conformal fixed fields to doses of 50-55 Gy in 30-33 daily fractions. Tumours were relatively large with a median gross tumour volume (GTV) of 17.9 cm3 (range 2.5-183 cm3).

RESULTS

At a median follow-up of 21 months (range 6-62 months) none of 41 patients have recurred. The current imaging tumour control rate is 100% at 1 and 3 years. The actuarial survival at 2 years is 100% and 91% at 3 and 5 years. Following SCRT tumour decreased in size in 9 patients. SCRT was well tolerated. Five patients had improvement in vision, and six patients improvement in cranial nerve function. Two patients whose planning target volume (PTV) included the sella developed hypopituitarism during and at 18 months after SCRT. One patient with pre-existing hydrocephalus due to pineal region meningioma developed cognitive impairment 7 months after treatment. One patient with involvement of the optic nerve had visual deterioration at 18 months.

CONCLUSIONS

SCRT is a feasible high precision irradiation technique for residual and recurrent skull base meningiomas including both small and larger tumours with excellent early tumour control and low toxicity. Longer follow-up is necessary to demonstrate sustained tumour control and low morbidity of such high precision localized method of fractionated irradiation.

Conformal radiotherapy for brain tumors

The technical improvements of three-dimensional conformal radiotherapy can decrease the toxicity of brain treatment to acceptable levels. The adoption of the technique by more centers would allow for the potential advantages of three-dimensional radiotherapy to be employed in a greater number of patients. Further studies evaluating the use of three-dimensional conformal radiotherapy in patients with nervous system neoplasms should focus on determining the effects on quality of life for the patient and survival compared with more standard treatment techniques.