Radiation treatment strategies for acromegaly

Surgery for acromegaly: Indications and goals

Acromegaly is a disease that occurs secondary to high levels of GH, most often from a hormone-secreting pituitary adenoma, with multisystem adverse effects. Diagnosis includes serum GH and IGF-1 levels, and obtaining an MRI pituitary protocol to assess for a functional pituitary adenoma. Attempted gross total resection of the GH-secreting adenoma is the gold standard in treatment for patients with acromegaly for a goal of biochemical remission. Medical and radiation therapies are available when patients do not achieve biochemical cure after surgical therapy.

[Use of chemotherapy in the treatment of aggresive pituitary adenomas]

AIM

To clarify the concept of 'aggressive pituitary adenoma' using analysis of the current concepts, as well as to determine the optimal treatment algorithm for this disease and the place of chemotherapy in this treatment. Pituitary adenomas comprise from 10 to 15% of intracranial neoplasms. Despite the fact that pituitary adenomas are benign neoplasms, in 25-55% of cases they demonstrate invasive growth, growing into the surrounding structures (sphenoid sinus, cavernous sinus, etc.). Due to the lack of a standard definition of aggressive pituitary adenomas (due to the lack of clear criteria for this disease), there are no studies in the literature reporting optimal treatment for this group of patients, except for several publications describing the use of Temozolomide as palliative therapy.

Growth hormone and prolactin-staining tumors causing acromegaly: a retrospective review of clinical presentations and surgical outcomes

OBJECTIVE

Acromegaly results in disfiguring growth and numerous medical complications. This disease is typically caused by growth hormone (GH)-secreting pituitary adenomas, which are treated first by resection, followed by radiation and/or medical therapy if needed. A subset of acromegalics have dual-staining pituitary adenomas (DSPAs), which stain for GH and prolactin. Presentations and treatment outcomes for acromegalics with DSPAs are not well understood.

METHODS

The authors retrospectively reviewed the records of more than 5 years of pituitary adenomas resected at their institution. Data were collected on variables related to clinical presentation, tumor pathology, radiological size, and disease recurrence. The Fisher's exact test, ANOVA, Student t-test, chi-square test, and Cox proportional hazards and multiple logistic regression were used to measure statistical significance.

RESULTS

Of 593 patients with pituitary adenoma, 91 presented with acromegaly. Of these 91 patients, 69 (76%) had tumors that stained for GH only (single-staining somatotrophic adenomas [SSAs]), while 22 (24%) had tumors that stained for GH and prolactin (DSPAs). Patients with DSPAs were more likely to present with decreased libido (p = 0.012), signs of acromegalic growth (p = 0.0001), hyperhidrosis (p = 0.0001), and headaches (p = 0.043) than patients with SSAs. DSPAs presented with significantly higher serum prolactin (60.7 vs 10.0 µg/L, p = 0.0002) and insulin-like growth factor-1 (IGF-1) (803.6 vs 480.0 ng/ml, p = 0.0001), and were more likely to have IGF-1 levels > 650 ng/ml (n = 13 [81.3%] vs n = 6 [21.4%], p = 0.0001) than patients with SSAs despite similar sizes (1.8 vs 1.7 cm, p = 0.5). Patients with DSPAs under 35 years of age were more likely to have a recurrence (n = 4 [50.0%] vs n = 3 [11.1%], p = 0.01) than patients with SSAs under the age of 35. DSPA patients were less likely to achieve remission with surgery than SSA patients (n = 2 [20%] vs n = 19 [68%], p = 0.01). Univariate analysis identified single-staining tumors (p = 0.02), gross-total resection (p = 0.02), and tumor diameter (p = 0.05) as predictors of surgical remission. Multiple logistic regression demonstrated that SSAs (p = 0.04) were independently associated with surgical remission of acromegaly. Kaplan-Meier analysis revealed that DSPAs had more time until disease remission (p = 0.033).

CONCLUSIONS

Acromegalics with tumors that stain for prolactin and GH, which represented almost a quarter of acromegalics in this cohort, had more aggressive clinical presentations and postoperative outcomes than SSAs. Prolactin staining provides useful information for acromegalics undergoing pituitary surgery.

Malaysian Consensus Statement for the Diagnosis and Management of Acromegaly

In Malaysia, acromegaly is under-recognised with only 10-15% of the expected number of cases from prevalence estimates, having been diagnosed and managed in established endocrine centres with access to multidisciplinary care. This is mainly due to lack of awareness and standardised approach in diagnosing this disease resulting in delay in diagnosis and management with suboptimal treatment outcomes. This first Malaysian consensus statement on the diagnosis and management of acromegaly addresses these issues and is based on current best practices and latest available evidence so as to reduce the disease burden on acromegaly patients managed in the Malaysian healthcare system.

Management of aggressive growth hormone secreting pituitary adenomas

Aggressive GH-secreting pituitary adenomas (GHPAs) represent an important clinical problem in patients with acromegaly. Surgical therapy, although often the mainstay of treatment for GHPAs, is less effective in aggressive GHPAs due to their invasive and destructive growth patterns, and their proclivity for infrasellar invasion. Medical therapies for GHPAs, including somatostatin analogues and GH receptor antagonists, are becoming increasingly important adjuncts to surgical intervention. Stereotactic radiosurgery serves as an important fallback therapy for tumors that cannot be cured with surgery and medications. Data suggests that patients with aggressive and refractory GHPAs are best treated at dedicated tertiary pituitary centers with multidisciplinary teams of neuroendocrinologists, neurosurgeons, radiation oncologists and other specialists who routinely provide advanced care to GHPA patients. Future research will help clarify the defining features of "aggressive" and "atypical" PAs, likely based on tumor behavior, preoperative imaging characteristics, histopathological characteristics, and molecular markers.

Need for improved monitoring in patients with acromegaly

Acromegaly is a rare and insidious disease characterized by the overproduction of growth hormone (GH) and insulin-like growth factor 1 (IGF1) and is most commonly due to a pituitary adenoma. Patients with acromegaly who experience prolonged exposure to elevated levels of GH and IGF1 have an increased mortality risk and progressive worsening of disease-related comorbidities. Multimodal treatment with surgery, medical therapy, and radiotherapy provides biochemical control, defined by recent acromegaly clinical guidelines from the Endocrine Society as a reduction of GH levels to <1.0 ng/ml and normalization of IGF1 levels, to a substantial proportion of patients and is associated with improved clinical outcomes. Patients with acromegaly, even those without clinical symptoms of disease, require long-term monitoring of GH and IGF1 levels if the benefits associated with biochemical control are to be maintained and the risk of developing recurrent disease is to be abated. However, suboptimal monitoring is common in patients with acromegaly, and this can have negative health effects due to delays in detection of recurrent disease and implementation of appropriate treatment. Because of the significant health consequences associated with prolonged exposure to elevated levels of GH and IGF1, optimal monitoring in patients with acromegaly is needed. This review article will discuss the biochemical assessments used for therapeutic monitoring in acromegaly, the importance of monitoring after surgery and medical therapy or radiotherapy, the consequences of suboptimal monitoring, and the need for improved monitoring algorithms for patients with acromegaly.

LIMITATIONS OF CURRENT APPROACHES FOR THE TREATMENT OF ACROMEGALY

OBJECTIVE

Acromegaly is a rare disease characterized by hypersecretion of growth hormone (GH), typically from a benign pituitary somatotroph adenoma, that leads to subsequent hypersecretion of insulin-like growth factor 1 (IGF-1). Patients with acromegaly have an increased risk of mortality and progressive worsening of comorbidities. Surgery, medical therapy, and radiotherapy are currently available treatment approaches for patients with acromegaly, with overall therapeutic goals of lowering GH levels and achieving normal IGF-1 levels, reducing tumor size, improving comorbidities, and minimizing mortality risk. Although surgery can lead to biochemical remission in some patients with acromegaly, many patients will continue to have uncontrolled disease and require additional treatment.

METHODS

We reviewed recently published reports and present a summary of the safety and efficacy of current treatment modalities for patients with acromegaly.

RESULTS

A substantial proportion of patients who receive medical therapy or radiotherapy will have persistently elevated GH and/or IGF-1. Because of the serious health consequences of continued elevation of GH and IGF-1, there is a need to improve therapeutic approaches to optimize biochemical control, particularly in high-need patient populations for whom current treatment options provide limited benefit.

CONCLUSION

This review discusses current treatment options for patients with acromegaly, limitations associated with each treatment approach, and areas within the current treatment algorithm, as well as patient populations for which improved therapeutic options are needed. Novel agents in development were also highlighted, which have the potential to improve management of patients with uncontrolled or persistent acromegaly.

Multi-modal management of acromegaly: a value perspective

PURPOSE

The Acromegaly Consensus Group recently released updated guidelines for medical management of acromegaly patients. We subjected these guidelines to a cost analysis.

METHODS

We conducted a cost analysis of the recommendations based on published efficacy rates as well as publicly available cost data. The results were compared to findings from a previously reported comparative effectiveness analysis of acromegaly treatments. Using decision tree software, two models were created based on the Acromegaly Consensus Group's recommendations and the comparative effectiveness analysis. The decision tree for the Consensus Group's recommendations was subjected to multi-way tornado analysis to identify variables that most impacted the value analysis of the decision tree.

RESULTS

The value analysis confirmed the Consensus Group's recommendations of somatostatin analogs as first line therapy for medical management. Our model also demonstrated significant value in using dopamine agonist agents as upfront therapy as well. Sensitivity analysis identified the cost of somatostatin analogs and growth hormone receptor antagonists as having the most significant impact on the cost effectiveness of medical therapies.

CONCLUSION

Our analysis confirmed the value of surgery as first-line therapy for patients with surgically accessible lesions. Surgery provides the greatest value for management of patients with acromegaly. However, in accordance with the Acromegaly Consensus Group's recent recommendations, somatostatin analogs provide the greatest value and should be used as first-line therapy for patients who cannot be managed surgically. At present, the substantial cost is the most significant negative factor in the value of medical therapies for acromegaly.

Surgical outcomes using a medial-to-lateral endonasal endoscopic approach to pituitary adenomas invading the cavernous sinus

OBJECT

This study details the extent of resection and complications associated with endonasal endoscopic surgery for pituitary tumors invading the cavernous sinus (CS) using a moderately aggressive approach to maximize extent of resection through the medial CS wall while minimizing the risk of cranial neuropathy and blood loss. Tumor in the medial CS was aggressively pursued while tumor in the lateral CS was debulked in preparation for radiosurgery.

METHODS

A prospective surgical database of consecutive endonasal pituitary surgeries with verified CS invasion on intraoperative visual inspection was reviewed. The extent of resection as a whole and within the CS was assessed by an independent neuroradiologist using pre- and postoperative Knosp-Steiner (KS) categorization and volumetrics of the respective MR images. The extent of resection and clinical outcomes were compared for medial (KS 1-2) and lateral (KS 3-4) lesions.

RESULTS

Thirty-six consecutive patients with pituitary adenomas involving the CS who had surgery via an endonasal endoscopic approach were identified. The extent of resection was 84.6% for KS 1-2 and 66.6% for KS 3-4 (p = 0.04). The rate of gross-total resection was 53.8% for KS 1-2 and 8.7% for KS 3-4 (p = 0.0006). Six patients (16.7%) had preoperative cranial neuropathies, and all 6 had subjective improvement after surgery. Surgical complications included 2 transient postoperative cranial neuropathies (5.6%), 1 postoperative CSF leak (2.8%), 1 reoperation for mucocele (2.8%), and 1 infection (2.8%).

CONCLUSIONS

The endoscopic endonasal "medial-to-lateral" approach permits safe debulking of tumors in the medial and lateral CS. Although rates of gross-total resection are moderate, particularly in the lateral CS, the risk of permanent cranial neuropathy is extremely low and there is a high chance of improvement of preexisting deficits. This approach can also facilitate targeting for postoperative radiosurgery.

Initial experiences with endoscopic rhino-neurosurgery in Amsterdam

Endoscopic surgery of the skull base has been on the rise for several years. Endoscopic access for surgery can be achieved from the frontal sinus anteriorly along the skull base to the odontoid process posterior inferiorly. An endoscope is inserted through one nasal corridor and allows visualization of the working field and up to three surgical instruments can be used to address the lesion. This is called the "two nostrils-four hands technique". This is a retrospective study of 67 cases. Setting of the study is an Amsterdam University hospital. Cases were identified in the department of otorhinolaryngology and department of neurosurgery database. All patients operated between 1 January, 2008 and 1 February, 2012 with pituitary tumours that extend beyond the sella, sinonasal tumours and all non-pituitary skull-base tumours were included. Mean tumour diameter was 3.8 cm. We performed a near-to-gross total resection in 92% of cases where we intended to perform a total resection. The most frequent complication was CSF leakage. This study demonstrates that this technique is safe and reliable. What is needed is a dedicated team, which includes a dedicated anesthesiologist, endocrinologist, ophthalmologist, and radiation oncologist.

Development of a modified head and neck quality assurance phantom for use in stereotactic radiosurgery trials

An anthropomorphic head phantom, constructed from a water‐equivalent plastic shell with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25 Gy to 90% of the GTV, with ≤10% of the OAR volume receiving ≥8Gy for the phantom trial. The modified phantom was used to test the rigor of the treatment planning process and phantom reproducibility using a Gamma Knife, CyberKnife, and linear accelerator (linac)‐based radiosurgery system. Delivery reproducibility was tested by repeating each irradiation three times. TLD results from three irradiations on a CyberKnife and Gamma Knife agreed with the calculated target dose to within ± 4% with a maximum coefficient of variation of ±2.1%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.4% and 99.5% using ±5%/3mm criteria, respectively. Results from the linac irradiation were within ±6.2% for TLD with a coefficient of variation of ±0.1%. Distance to agreement was calculated to be 1.2 mm and 1.3 mm along the inferior and superior edges of the target in the sagittal film plane, and 1.2 mm for both superior and inferior edges in the coronal film plane. A modified, anatomically realistic SRS phantom was developed that provided a realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI‐funded clinical trials.

PACS number: 87.55 ‐v

Orbital metastasis of pituitary growth hormone secreting carcinoma causing lateral gaze palsy

Background:

Although pituitary adenoma is one of the most common intracranial tumors, it rarely progresses secondarily into a metastatic carcinoma. Commonalities in reported cases include subtotal resection at presentation, treatment with radiation therapy, and delayed metastatic progression. Pathologic descriptions of these lesions are varying and inconsistent.

Case Description:

A 52-year-old male was diagnosed with acromegaly and pituitary tumor in 1996. He underwent four subtotal resections and five courses of stereotactic radiosurgery over 14 years. He developed left eye lateral gaze palsy, and was found to have a distant orbital metastasis with involvement of the left lateral rectus and lateral orbital wall. He underwent left orbital craniotomy via eyebrow incision for resection of this lesion. Pathologic evaluation showed a markedly elevated Ki67 level of 30%.

Conclusion:

While overall incidence of metastatic progression of pituitary adenoma after radiotherapy appears to be low, it appears to be a possible complication, and could be more likely in patients receiving multiple doses of radiotherapy. Our review of reported cases showed that 45/46 (97.8%) of patients developing carcinoma had prior radiation exposure. These patients may also have more aggressive pathologic characteristics of their lesions.

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.

Gamma knife radiosurgery for acromegaly

Acromegaly is debilitating disease occasionally refractory to surgical and medical treatment. Stereotactic radiosurgery, and in particular Gamma Knife surgery (GKS), has proven to be an effective noninvasive adjunct to traditional treatments, leading to disease remission in a substantial proportion of patients. Such remission holds the promise of eliminating the need for expensive medications, along with side effects, as well as sparing patients the damaging sequelae of uncontrolled acromegaly. Numerous studies of radiosurgical treatments for acromegaly have been carried out. These illustrate an overall remission rate over 40%. Morbidity from radiosurgery is infrequent but can include cranial nerve palsies and hypopituitarism. Overall, stereotactic radiosurgery is a promising therapy for patients with acromegaly and deserves further study to refine its role in the treatment of affected patients.

Surgery and radiosurgery for acromegaly: a review of indications, operative techniques, outcomes, and complications

Among multimodality treatments for acromegaly, the goals of surgical intervention are to balance maximal tumor resection while preserving normal pituitary function and maintaining patient safety. The resection of growth hormone-(GH-) secreting pituitary adenomas in the hands of experienced surgeons results in hormonal remission in 50-70% of patients. Acromegalic patients often have medical comorbidities and anatomical variations complicating anesthesia and surgical management. Despite these challenges, complications such as CSF leak or new hypopituitarism following surgery remain uncommon. Over the past decade, endoscopic approaches to pituitary tumors have improved visualization and facilitated identification of additional tumor using angled telescopes. Patients with persistent acromegaly following surgery require continued medical and/or radiation-based interventions. The adjunctive use of stereotactic radiosurgery offers hormonal remission in 40-50% of patients. In this article, the current preoperative evaluation, indications for surgery, surgical approaches, role of radiosurgery, complications, and remission criteria following operative resection of GH adenomas are reviewed.

Clinical review: Pituitary carcinoma: difficult diagnosis and treatment

CONTEXT

Although pituitary tumors are common, pituitary carcinoma is very rare and is only diagnosed when pituitary tumor noncontiguous with the sellar region is demonstrated. Diagnosis is difficult, resulting in delays that may adversely effect outcome that is traditionally poor. Barriers to earlier diagnosis and management strategies for pituitary carcinoma are discussed.

EVIDENCE ACQUISITION

PubMed was employed to identify relevant studies, a review of the literature was conducted, and data were summarized and integrated from the author's perspective.

EVIDENCE SYNTHESIS

The available data highlight the difficulties in diagnosis and management and practical challenges in conducting clinical trials in this rare condition. They suggest that earlier diagnosis with aggressive multimodal therapy may be advantageous in some cases.

CONCLUSIONS

Although pituitary carcinoma remains difficult to diagnose and treat, recent developments have led to improved outcomes in selected cases. With broader use of molecular markers, efforts to modify current histopathological criteria for pituitary carcinoma diagnosis may now be possible. This would assist earlier diagnosis and, in combination with targeted therapies, potentially improve long-term survival.

Nelfinavir induces radiation sensitization in pituitary adenoma cells

Pituitary adenomas with local invasion and high secretory activity remain a therapeutic challenge. The HIV protease inhibitor nelfinavir is a radiosensitizer in multiple tumor models. We tested nelfinavir as a radiosensitizer in pituitary adenoma cells in vitro and in vivo. We examined the effect of nelfinavir with radiation on in vitro cell viability, clonogenic survival, apoptosis, prolactin secretion, cell cycle distribution, and the PI3K-AKT-mTOR pathway. We evaluated tumor growth delay and confirmed nelfinavir's effect on the PI3K-AKT-mTOR pathway in a hind-flank model. Nelfinavir sensitized pituitary adenoma cells to ionizing radiation as shown by viability assays and clonogenic assay with an enhancement ratio of 1.2 (p < 0.05). There is increased apoptotic cell death, as determined by annexin-V expression and cleaved caspase-3 levels. Nelfinavir does not affect prolactin secretion or cell cycle distribution. In vivo, untreated tumors reached 4-fold volume in 12 days, 17 days with nelfinavir treatment, 27 days with radiation 6 Gy, and 41 days with nelfinavir plus radiation (one-way ANOVA p < 0.001). Decreased phospho-S6 on Western blotting in vitro and immunohistochemistry in vivo demonstrated nelfinavir inhibition of the PI3K-AKT-mTOR pathway. Our data suggests a promising combination therapy with nelfinavir plus radiation in pituitary adenomas, which should be investigated in clinical studies.

Therapy of aggressive pituitary tumors

INTRODUCTION

Aggressive tumors of the pituitary gland are classically defined as pituitary tumors with a massive invasion of the surrounding anatomical structures and rapid growth. They are notoriously difficult to manage and are associated with poor prognosis because the therapeutic options are limited and the tumors are generally unresponsive to therapy.

AREAS COVERED

This review focuses on treatment options for aggressive pituitary tumors, including surgery, radiotherapy and medical treatment, as well as focusing on the promising therapeutic options for aggressive pituitary tumors, evaluating the literature of the last 15 years. With the exception of prolactinomas, surgery is the first-line option, but most aggressive pituitary tumors often require repeated surgery. Pharmacotherapies are useful when surgery is unlikely to improve symptoms, or as an adjunct therapy to surgery. In prolactinomas, dopamine agonists are the first-line treatment and normalize prolactin levels in most patients, even those with macroprolactinomas. Somatostatin analogs are effective agents for primary therapy, pre-operatively or post-operatively to control tumor re-expansion of pituitary adenomas. However, dopamine agonists and somatostatin analogs are not as effective as they are for the treatment of non-aggressive adenomas. When surgery and pharmacotherapy fail, radiotherapy is a useful third-line strategy. Conventional chemotherapy is poorly effective but recent case reports with the temozolomide, an alkylating agent, have provided better results in the short term.

EXPERT OPINION

Aggressive pituitary tumors are associated with poor prognosis as therapeutic options are limited. Moreover, they tend to recur quickly after initial treatment, are generally unresponsive to therapy, and are difficult to manage. To improve the overall response rate, the early application of current therapeutic approaches with the incorporation of new therapeutic developments is mandatory.