Pituitary radiotherapy: current controversies

Current perspectives on recurrent pituitary adenoma: The role and timing of surgery vs adjuvant treatment

The clinical course of pituitary adenoma can be highly variable. Aggressive pituitary tumours may require multimodal therapy with multiple operations. Even standard pituitary adenomas exhibit relatively high long-term recurrence rates and delayed intervention is often required. The indications for revision surgery in the endoscopic era are expanding for both functioning and nonfunctioning tumours, including access to the cavernous sinus and intracranial compartments. Although revision surgery can be challenging, it has been demonstrated to be both safe and effective. The question of the use of early radiotherapy in pituitary adenoma remains controversial. Our increasing understanding of pituitary tumour biology facilitates individualized treatment and surveillance protocols, with early intervention in high-risk adenoma subtypes. In this review, we discuss the treatment options for recurring pituitary tumours and focus on the role of revision surgery.

A comparison of the doses received by normal cranial tissues during different simple model conventional radiotherapeutic approaches to pituitary tumours

This aim of this study was to compare the doses received by critical cranial organs when three different radiation techniques were used to treat pituitary tumours. Cranial computed tomography scans of a RANDO phantom and 30 patients were used for pituitary macroadenoma radiotherapy treatment planning. For each slice, target volumes and other critical organs were contoured and three techniques were applied: (A) two parallel-opposed lateral fields, (B) two oblique fields (45°) in coronal plane and (C) two parallel-opposed lateral and anterior fields while the head was tilted 45° in the sagittal plane. The doses received by the target volume and the critical organs for each technique were calculated for all patients. Irradiation was repeated three times for each technique. Finally, the doses that reached the organs of interest resulting from these techniques were compared. The dose delivered to the temporal lobes was 105, 9 and 72 % of the prescribed dose using techniques A, B and C, respectively. The dose received by the cochlea was the lowest in technique C (27 % of prescribed dose) compared with techniques A (79 %) and B (48 %). All techniques delivered 100 % of the prescribed dose to the chiasma. Technique A increased the dose to temporal lobes and the cochlea to such an extent that they exceeded the tolerance dose. Technique B spared the temporal lobes better than technique C; however, technique C was preferred since the dose received by the cochlea in this case was the lowest of all techniques. None of the techniques spared the chiasma.

Extensive experience in the management of macroprolactinomas

OBJECTIVES

Macroprolactinomas are pituitary tumours that can be managed with dopamine agonists (DA), surgery and radiotherapy. We aimed to assess the outcomes of these treatment modalities.

DESIGN

Retrospective case-note study of patients managed in a single tertiary referral centre.

PATIENTS

One hundred patients (68 male) diagnosed with macroprolactinoma between 1971 and 2009.

MEASUREMENTS

We assessed the response to first-line treatment in terms of reduction in serum prolactin, endocrine status, symptomatic improvement and tumour shrinkage. Patients were divided into a group that received only DA therapy and a group that received surgery, radiotherapy or both, with or without a DA. We compared pituitary function at baseline and at last clinic visit between the two groups.

RESULTS

In total, there were 1170 patient years of follow-up. Pituitary surgery was performed in 29/100 patients. Fourteen patients received pituitary radiotherapy (8/14 surgery also). At last clinic visit, the nonmedical therapy group had a higher risk of gonadotrophin deficiency (77·4% vs 44·8%, P = 0·0037), TSH deficiency (54·8% vs 25·4%, P = 0·0009) and ACTH deficiency (56·2% vs 17·2%, P = 0·0001). When last reviewed, 23/29 (79·3%) patients who underwent surgery and 10/14 (71·4%) patients who received radiotherapy were taking a DA.

CONCLUSIONS

Treatment with a DA alone is associated with better outcomes in terms of pituitary function and as such represents the optimal first-line therapy for macroprolactinomas. Surgery and radiotherapy should be reserved for patients who are either intolerant of or resistant to DAs. Following surgery and/or radiotherapy, the majority of patients still require a DA for control of prolactin hypersecretion.

Cranial nerve dysfunction following Gamma Knife surgery for pituitary adenomas: long-term incidence and risk factors

OBJECT

Gamma Knife surgery (GKS) has become a significant component of neurosurgical treatment for recurrent secretory and nonsecretory pituitary adenomas. Although the long-term risks of visual dysfunction following microsurgical resection of pituitary adenomas has been well studied, the comparable risk following radiosurgery is not well defined. This study evaluates the long-term risks of ophthalmological dysfunction following GKS for recurrent pituitary adenomas.

METHODS

An analysis of 217 patients with recurrent secretory (n = 131) and nonsecretory (n = 86) pituitary adenomas was performed to determine the incidence of and risk factors for subsequent development of visual dysfunction. Patients underwent ophthalmological evaluation as part of post-GKS follow-up to assess for new or worsened cranial nerve II, III, IV, or VI palsies. The median follow-up duration was 32 months. The median maximal dose was 50 Gy, and the median peripheral dose was 23 Gy. A univariate analysis was performed to assess for risk factors of visual dysfunction post-GKS.

RESULTS

Nine patients (4%) developed new visual dysfunctions, and these occurred within 6 hours to 34 months following radiosurgery. None of these 9 patients had tumor growth on post-GKS neuroimaging studies. Three of these patients had permanent deficits whereas in 6 the deficits resolved. Five of the 9 patients had prior GKS or radiotherapy, which resulted in a significant increase in the incidence of cranial nerve dysfunction (p = 0.0008). An increased number of isocenters (7.1 vs 5.0, p = 0.048) was statistically related to the development of visual dysfunction. Maximal dose, margin dose, optic apparatus dose, tumor volume, cavernous sinus involvement, and suprasellar extension were not significantly related to visual dysfunction (p >0.05).

CONCLUSIONS

Neurological and ophthalmological assessment in addition to routine neuroimaging and endocrinological follow-up are important to perform following GKS. Patients with a history of radiosurgery or radiation therapy are at higher risk of cranial nerve deficits. Also, a reduction in the number of isocenters delivered, along with volume treated, particularly in the patients with secretory tumors, appears to be the most reasonable strategy to minimize the risk to the visual system when treating recurrent pituitary adenomas with stereotactic radiosurgery.

Cognitive performance after postoperative pituitary radiotherapy: a dosimetric study of the hippocampus and the prefrontal cortex

OBJECTIVE

The hippocampus and prefrontal cortex (PFC) are important for memory and executive functioning and are known to be sensitive to radiotherapy (RT). Radiation dosimetry relates radiation exposure to specific brain areas. The effects of various pituitary RT techniques were studied by relating detailed dosimetry of the hippocampus and PFC to cognitive performance.

METHODS

In this cross-sectional design, 75 non-functioning pituitary macroadenoma (NFA) patients (61±10 years) participated and were divided into irradiated (RT+, n=30) and non-irradiated (RT-, n=45) groups. The RT+ group (who all received 25 fractions of 1.8 Gy; total dose: 45 Gy) consisted of three RT technique groups: three-field technique, n=10; four-field technique, n=15; and five-field technique, n=5. Memory and executive functioning were assessed by standardized neuropsychological tests. A reconstruction of the dose distributions for the three RT techniques was made. The RT doses on 30, 50, and 70% of the volume of the left and right hippocampus and PFC were calculated.

RESULTS

Cognitive test performance was not different between the four groups, despite differences in radiation doses applied to the hippocampi and PFC. Age at RT, time since RT, and the use of thyroid hormone varied significantly between the groups; however, they were not related to cognitive performance.

CONCLUSION

This study showed that there were no significant differences on cognitive performance between the three-, four-, and five-field RT groups and the non-irradiated patient group. A dose-response relationship could not be established, even with a radiation dose that was higher on most of the volume of the hippocampus and PFC in case of a four-field RT technique compared with the three- and five-field RT techniques.

Cognitive functioning in patients treated for nonfunctioning pituitary macroadenoma and the effects of pituitary radiotherapy

CONTEXT AND OBJECTIVE

Cognitive deterioration is reported in patients with a nonfunctioning pituitary macroadenoma (NFA) and after pituitary radiotherapy. However, reported results are inconsistent and are potentially confounded by different underlying pituitary disorders. The aim of this study was to examine cognitive functions in patients previously treated for NFA with or without radiotherapy.

DESIGN

Verbal memory was assessed with the Dutch equivalent to the Rey Auditory Verbal Learning Test (15 Words Test, 15 WT). Executive functioning was examined using the Ruff Figural Fluency Test (RFFT). We compared our patient cohort with large reference populations representative of the Dutch population.

PATIENTS

Eighty-four patients (62±10 years) who underwent transsphenoidal surgery 8.6±6.3 years earlier participated. Patients who underwent radiotherapy (n=39) were compared to those who received surgery alone (n=45). All patients were on stable hormonal replacement therapy.

RESULTS

The total patient group scored significantly below the reference sample on all 15 WT z-scores (95%CI): short-term memory, -0.3 (-0.5 to -0.1); total memory, -0.8 (-1.1 to -0.5); learning score, -0.3 (-0.5 to -0.1); delayed memory, -0.8 (-1.1 to -0.5), all P<0.01. The total patient group scored significantly below the reference sample on RFFT z-scores (95%CI): unique designs, -0.7 (-0.9 to -0.5) and perseverative errors, -0.5 (-0.8 to -0.2), both P<0.001. Patients who underwent radiotherapy showed no significant differences on cognition when compared to those who received surgery alone.

CONCLUSION

Patients with NFA score significantly worse on cognition compared to reference populations. Radiotherapy does not appear to have a major influence on cognition.

ACTH deficiency, higher doses of hydrocortisone replacement, and radiotherapy are independent predictors of mortality in patients with acromegaly

CONTEXT

A number of retrospective studies report that patients with acromegaly have increased morbidity and premature mortality, with standardized mortality ratios (SMR) of 1.3-3. Many patients with acromegaly develop hypopituitarism as a result of the pituitary adenoma itself or therapies such as surgery and radiotherapy. Pituitary radiotherapy and hypopituitarism have also been associated with an increased SMR.

METHODS

Using the West MIDLANDS: Acromegaly database (n = 501; 275 female), we assessed the influence of prior radiotherapy and hypopituitarism (and replacement therapy) on mortality in patients with acromegaly. Median duration of follow-up was 14.0 yr (interquartile range, 7.9-21 yr).

RESULTS

All-cause mortality was elevated [SMR, 1.7 (1.4, 2.0); P < 0.001]. On external analysis, prior radiotherapy, ACTH, and gonadotropin deficiency were associated with an elevated SMR [radiotherapy SMR, 2.1 (1.7-2.6); P = 0.006; ACTH deficiency SMR, 2.5 (1.9-3.2); P < 0.0005; and gonadotropin deficiency SMR, 2.1 (1.6-2.7); P = 0.037]. On internal analysis, the relative risk (RR) of mortality was increased in the radiotherapy [RR, 1.8 (1.2-2.8); P = 0.008] and ACTH-deficiency groups [RR, 1.7 (1.2-2.5); P = 0.004], but not in the gonadotropin- or TSH-deficiency groups. In the ACTH-deficient group, increased replacement doses of hydrocortisone greater than 25 mg/d were associated with increased mortality compared to lower doses.

CONCLUSIONS

Radiotherapy and ACTH deficiency are significantly associated with increased mortality in patients with acromegaly. In ACTH-deficient patients, a daily dose of more than 25 mg hydrocortisone is associated with increased mortality compared to lower doses. These results have important implications for the treatment of patients with acromegaly and also raise issues as to the optimum hydrocortisone treatment regimens for ACTH-deficient patients.

O(6)-methylguanine DNA methyltransferase immunoexpression in nonfunctioning pituitary adenomas: are progressive tumors potential candidates for temozolomide treatment?

BACKGROUND

Currently, no effective alternative treatment exists for progressive, regrowing, nonfunctioning pituitary adenomas (NFPA) that are resistant to conventional multimodality therapy. Temozolomide (TMZ) was proposed as a treatment option for pituitary carcinomas and aggressive pituitary adenomas. Recently, it was suggested that the responsiveness of pituitary tumors to TMZ depends on the immunoexpression of O(6)-methylguanine DNA methyltransferase (MGMT). Therefore, the authors of this report assessed MGMT expression in a series of patients with progressive, regrowing NFPAs to evaluate whether TMZ may serve as alternative treatment option.

METHODS

On the basis of postoperative magnetic resonance imaging, 45 patients with NFPAs were allocated to either a group with progressive, regrowing tumors (n = 24) or a tumor-free group (n = 21), which served as a control. MGMT expression was assessed semiquantitatively by immunohistochemistry (low expression was defined as <or=50% immunostained adenoma cells, and high expression was defined as >50% immunostained adenoma cells) and was compared between the 2 groups.

RESULTS

At the time of initial surgery, low MGMT expression was observed in 12 of 24 patients (50%) in the study group with progressive, regrowing NFPAs. In the control group of tumor-free patients, only 5 of 21 patients (24%) exhibited low MGMT expression. A comparable distribution of MGMT expression was observed in the specimens from repeat surgeries. A shorter interval to second surgery was observed in patients who had low MGMT expression.

CONCLUSIONS

The current data has suggested that half of the patients with progressive, regrowing NFPAs exhibit low MGMT expression and are potential candidates for treatment with TMZ. These findings provide a rationale for the use of TMZ as an alternative treatment approach in this subgroup if conventional therapy, including reoperation, radiosurgery, and radiotherapy, fails.

Mortality following pituitary radiotherapy

External beam radiotherapy has been used in the management of pituitary adenomas for nearly a century, preventing tumor regrowth following surgery for non-functioning pituitary adenomas and suppressing functional hypersecretion in those which are hormonally active. However, it has been linked with a number of potentially significant complications including formation of secondary intracranial tumors, cognitive impairment, hypopituitarism and cerebrovascular disease, as well as increased mortality. Radiation may cause a variety of vascular injuries and hemodynamic changes to the cerebral vasculature, and several authors have reported cerebrovascular complications and an increase in cerebrovascular mortality in patients receiving radiotherapy for pituitary and other central nervous system tumors. Ten years following pituitary radiotherapy, over 50% of patients develop deficiencies in one or more anterior pituitary hormones. A number of studies have demonstrated increased mortality in patients with hypopituitarism, predominantly due to cerebrovascular and cardiovascular disease. However, no clear answer has emerged with regards to causation, and pituitary radiotherapy has only been linked directly to mortality in one of these studies. Questions remain unanswered, and the use of conventional external beam radiotherapy in the management of pituitary disease must involve a critical risk-benefit analysis in each case.

Triple jeopardy in the pituitary

Aggressive pituitary tumors are rare the pathogenesis is not well established. The development of pituitary tumor after apoplexy has also been rarely reported. We describe the sequential development of Cushing's disease, apoplexy and aggressive pituitary tumor in the same patient. A 31-year old male presented with eutopic ACTH dependent Cushing's syndrome which failed initial pituitary surgery. He underwent subsequent bilateral adrenalectomy for control of hypercortisolism. An episode of pituitary apoplexy then occurred which was followed by the development of a null-cell pituitary tumor. This second tumor exhibited an aggressive behavior with invasion into the surrounding structures and systemic spread clinically. This case provides important evidence for the hypotheses of the pathogenesis of aggressive pituitary tumors which could have arisen from surviving adenoma cells following apoplexy or as a de novo development of pituitary carcinoma from cells which were not part of the original adenoma. This is the first report of a transformation of Cushing's disease to an aggressive and invasive null cell tumor after pituitary irradiation, apoplexy and surgery.

Cushing's disease in dogs: cabergoline treatment

The treatment of pituitary-dependent hyperadrenocorticism (PDH) in dogs has for a long time been focused on inhibiting the adrenal gland using drugs such as o-p'-DDD, Ketoconazole and Trilostane, without attacking the primary cause: the corticotrophinoma. Corticotroph cells can express the D2 dopaminergic receptor; therefore cabergoline (Cbg) could be effective as a treatment. Follow-up over 4 years was carried out in 40 dogs with PDH that were treated with Cbg (0.07 mg/kg/week. Out of the 40 dogs, 17 responded to Cbg (42.5%). A year after the treatment, there was a significant decrease in ACTH (p<0.0001), alpha-MSH (p<0.01), urinary cortisol/creatinine ratio (p<0.001), and of the tumor size (p<0.0001) evaluated by nuclear magnetic resonance. Dogs responding to Cbg lived significantly longer (p<0.001) than those in the control group. To conclude, Cbg is useful in 42.5% of dogs with PDH, justifying its use as a treatment.

Long-term (up to 18 years) effects on GH/IGF-1 hypersecretion and tumour size of primary somatostatin analogue (SSTa) therapy in patients with GH-secreting pituitary adenoma responsive to SSTa

CONTEXT

The role of somatostatin analogues (SSTa) in the treatment of acromegaly.

OBJECTIVE

To evaluate the antihormonal and antitumour efficacy of long-term (up to 18 years) primary treatment with SSTa in patients with GH-secreting pituitary adenoma responsive to SSTa.

DESIGN

An open, prospective, single-centre, clinical study.

PATIENTS

Thirty-six acromegalic patients, aged 17-75 years (postoral glucose tolerance test GH > 1 microg/l, increased IGF-1 for age and sex), were monitored in a single centre and treated with SSTa as first-line therapy. The mean pretreatment GH level was 13.5 +/- 3.1 microg/l, and IGF-1 (as a percentage of the value over the normal range) was 302 +/- 26%. The patients had macroadenoma (n = 25), microadenoma (n = 8) or empty sella turcica (n = 3). The mean duration of treatment was 8 years (range 3-18 years). Hormonal and morphological monitoring was undertaken after 6 months, and then the patients were followed annually.

RESULTS

After 1 year, the mean GH and IGF-1 levels had reduced considerably (GH: 2.4 +/- 0.3 microg/l; IGF-1; 174 +/- 14%, P < 0.01), and they continued to decrease over 10 years, with a mean GH level of 1.6 +/- 0.1 microg/l and IGF-1 of 123 +/- 18% (P = 0.02). GH < 2 microg/l, normal IGF-1, or both were observed in 25 (70%), 24 (67%) and 21 (58%) patients, respectively. The mean reduction in tumour volume was 43% (range 13-97%) and shrinkage > 20% was obtained in 21 patients (72%). SSTa treatment was well tolerated with few digestive or metabolic side-effects.

CONCLUSION

Long-term (up to 18 years) treatment with SSTa used as first-line therapy is effective from both an antihormonal and antitumour perspective, and is well tolerated in acromegalic patients.

Radiotherapy is Not Associated With Reduced Quality of Life and Cognitive Function in Patients Treated for Nonfunctioning Pituitary Adenoma

PURPOSE

To assess the influence of different treatment modalities on long-term health-related quality of life (HR-QoL) and cognitive problems among patients who had been treated for nonfunctioning pituitary adenoma (NFA).

METHODS AND MATERIALS

Eighty-one patients (49 men and 32 women, aged 55 +/- 10 years) with a minimal follow-up period of 1 year after treatment for NFA participated in this cross-sectional study. Sixty-two patients were initially treated by transsphenoidal surgery and 19 by craniotomy. Subsequently, 45 of these 81 subjects (56%) received additional radiotherapy (RT) after surgery because of a tumor remnant or regrowth. All subjects filled in standardized questionnaires measuring HR-QoL, depression, fatigue, and cognitive problems.

RESULTS

Patients who underwent additional RT more frequently underwent a craniotomy and were younger at surgery, but not at entering this study. They also used more hormonal substitution. Most HR-QoL domains showed a similar score in patients who underwent RT when compared with patients who did not receive RT. However, vitality and physical functioning proved to be better in RT subjects, and RT subjects also had better scores for depression and physical and mental fatigue (all p < 0.05). Some aspects of HR-QoL of patients who have been successfully treated for NFA are reduced compared with the normal population, but this was much more pronounced in the group that did not receive RT. In multivariate analysis, RT remained significantly associated with improved HR-QoL. No differences in cognitive function scores were observed.

CONCLUSION

Postoperative RT in patients with NFA is not associated with reduced quality of life or cognition when compared with surgery alone.

Clinically non-functioning pituitary macroadenomas in the elderly

BACKGROUND AND AIMS

The aim of the present study was to evaluate the clinical presentation, characteristics and post-surgical outcome of non-functioning pituitary macroadenomas (NFPM) in elderly patients.

METHODS

27 patients (65-81 years; 13 Males, 14 Females) with NFPM (20-45 mm in diameter) were studied. The symptoms prompting neuroradiological studies were vision alterations in 52%, and dizziness, loss of memory, confusion, headache and depression in 29%; in 19% of patients, the disease was incidentally discovered during computed tomography (CT) or magnetic resonance imaging (MRI) for head trauma or cerebral ischemic attacks.

RESULTS

Endocrinological evaluation on diagnosis showed global anterior hypopituitarism in 33% and partial hypopituitarism in 37% of patients. Immunohistochemistry showed signs of neurosecretion in most NFPM (chromogranin-A in 55%, gonadotropins in 19%, ACTH in 3.7%). Ki-67 antigen expression was indicative of low proliferative activity. Surgery was highly effective in improving alterations in vision and compressive symptoms, but was unable to restore normal pituitary function in established hypopituitarism in most cases. Eight patients (31%) were free of disease on subsequent MRI (follow-up 1-6 years). In 18 (69%) patients, a post-surgical residue was present. Of these, 6 (33%) underwent radiotherapy in the following years, owing to an increase in the volume of the remnants, and six (33%) underwent additional surgical treatment, followed by radiotherapy for further signs of growth in two. In the remaining patients, a small intrasellar remnant was stable on yearly MRI.

CONCLUSIONS

in elderly patients, the development of hypopituitarism is often overlooked and the initial diagnosis of NFPM may be delayed. This can expose patients to the risks of unrecognized hypopituitarism and jeopardize post-surgical outcome.

Management of resistant prolactinomas

Resistance to dopamine agonists occurs in a subset of patients with prolactin-secreting pituitary tumors. The resistance is mediated by loss of pituitary D2 receptors and occurs in both microadenomas and macroadenomas. Cabergoline is the most effective dopamine agonist and tumors that do not respond to bromocriptine or quinagolide frequently respond to cabergoline. Treatment options include maximizing the dose of the dopamine agonist, changing agonists, trans-sphenoidal surgery and radiation therapy. The goal of therapy is to restore and maintain gonadal and neurologic function, and this might occur in the absence of a normal prolactin level or a significant change in tumor size. Trans-sphenoidal pituitary surgery should be reserved for patients who are intolerant of medical therapy, or in whom this has failed. Radiation therapy has a limited role in treatment of resistant prolactinomas and should be reserved for patients in whom medical and surgical therapy has failed.