Presurgical octreotide treatment in acromegaly

Surgical and non-surgical interventions for primary and salvage treatment of growth hormone-secreting pituitary adenomas in adults

BACKGROUND

Growth hormone (GH)-secreting pituitary adenoma is a severe endocrine disease. Surgery is the currently recommended primary therapy for patients with GH-secreting tumours. However, non-surgical therapy (pharmacological therapy and radiation therapy) may be performed as primary therapy or may improve surgical outcomes.

OBJECTIVES

To assess the effects of surgical and non-surgical interventions for primary and salvage treatment of GH-secreting pituitary adenomas in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, WHO ICTRP, and ClinicalTrials.gov. The date of the last search of all databases was 1 August 2022. We did not apply any language restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs of more than 12 weeks' duration, reporting on surgical, pharmacological, radiation, and combination interventions for GH-secreting pituitary adenomas in any healthcare setting.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts for relevance, screened for inclusion, completed data extraction, and performed a risk of bias assessment. We assessed studies for overall certainty of the evidence using GRADE. We estimated treatment effects using random-effects meta-analysis. We expressed results as risk ratios (RR) for dichotomous outcomes together with 95% confidence intervals (CI) or mean differences (MD) for continuous outcomes, or in descriptive format when meta-analysis was not possible.

MAIN RESULTS

We included eight RCTs that evaluated 445 adults with GH-secreting pituitary adenomas. Four studies reported that they included participants with macroadenomas, one study included a small number of participants with microadenomas. The remaining studies did not specify tumour subtypes. Studies evaluated surgical therapy alone, pharmacological therapy alone, or combination surgical and pharmacological therapy. Methodological quality varied, with many studies providing insufficient information to compare treatment strategies or accurately judge the risk of bias. We identified two main comparisons, surgery alone versus pharmacological therapy alone, and surgery alone versus pharmacological therapy and surgery combined. Surgical therapy alone versus pharmacological therapy alone Three studies with a total of 164 randomised participants investigated this comparison. Only one study narratively described hyperglycaemia as a disease-related complication. All three studies reported adverse events, yet only one study reported numbers separately for the intervention arms; none of the 11 participants were observed to develop gallbladder stones or sludge on ultrasonography following surgery, while five of 11 participants experienced any biliary problems following pharmacological therapy (RR 0.09, 95% CI 0.01 to 1.47; 1 study, 22 participants; very low-certainty evidence). Health-related quality of life was reported to improve similarly in both intervention arms during follow-up. Surgery alone compared to pharmacological therapy alone may slightly increase the biochemical remission rate from 12 weeks to one year after intervention, but the evidence is very uncertain; 36/78 participants in the surgery-alone group versus 15/66 in the pharmacological therapy group showed biochemical remission. The need for additional surgery or non-surgical therapy for recurrent or persistent disease was described for single study arms only. Surgical therapy alone versus preoperative pharmacological therapy and surgery Five studies with a total of 281 randomised participants provided data for this comparison. Preoperative pharmacological therapy and surgery may have little to no effect on the disease-related complication of a difficult intubation (requiring postponement of surgery) compared to surgery alone, but the evidence is very uncertain (RR 2.00, 95% CI 0.19 to 21.34; 1 study, 98 participants; very low-certainty evidence). Surgery alone may have little to no effect on (transient and persistent) adverse events when compared to preoperative pharmacological therapy and surgery, but again, the evidence is very uncertain (RR 1.23, 95% CI 0.75 to 2.03; 5 studies, 267 participants; very low-certainty evidence). Concerning biochemical remission, surgery alone compared to preoperative pharmacological therapy and surgery may not increase remission rates up until 16 weeks after surgery; 23 of 134 participants in the surgery-alone group versus 51 of 133 in the preoperative pharmacological therapy and surgery group showed biochemical remission. Furthermore, the very low-certainty evidence did not suggest benefit or detriment of preoperative pharmacological therapy and surgery compared to surgery alone for the outcomes 'requiring additional surgery' (RR 0.48, 95% CI 0.05 to 5.06; 1 study, 61 participants; very low-certainty evidence) or 'non-surgical therapy for recurrent or persistent disease' (RR 1.22, 95% CI 0.65 to 2.28; 2 studies, 100 participants; very low-certainty evidence). None of the included studies measured health-related quality of life. None of the eight included studies measured disease recurrence or socioeconomic effects. While three of the eight studies reported no deaths to have occurred, one study mentioned that overall, two participants had died within five years of the start of the study.

AUTHORS' CONCLUSIONS

Within the context of GH-secreting pituitary adenomas, patient-relevant outcomes, such as disease-related complications, adverse events and disease recurrence were not, or only sparsely, reported. When reported, we found that surgery may have little or no effect on the outcomes compared to the comparator treatment. The current evidence is limited by the small number of included studies, as well as the unclear risk of bias in most studies. The high uncertainty of evidence significantly limits the applicability of our findings to clinical practice. Detailed reporting on the burden of recurrent disease is an important knowledge gap to be evaluated in future research studies. It is also crucial that future studies in this area are designed to report on outcomes by tumour subtype (that is, macroadenomas versus microadenomas) so that future subgroup analyses can be conducted. More rigorous and larger studies, powered to address these research questions, are required to assess the merits of neoadjuvant pharmacological therapy or first-line pharmacotherapy.

Medical Treatment of Acromegaly with Dopamine Agonists or Somatostatin Analogs

Treatment of acromegaly aims to correct (or prevent) tumor compression of surrounding tissues by excising the disease-causing lesion and reduce growth hormone (GH) and IGF-1 levels to normal values. When surgery (the usual first-line treatment) fails to correct GH/IGF-1 hypersecretion, medical treatment with dopamine agonists (DAs; particularly cabergoline) or somatostatin analogs (SAs) can be used. The GH receptor antagonist pegvisomant is helpful in patients who are totally or partially resistant to SAs and can be given in association with both SAs and/or DAs. Thanks to this multistep therapeutic strategy, adequate hormonal disease control is achieved in most patients, giving them normal life expectancy. Comorbidities associated with acromegaly generally improve after treatment, but persistent sequelae may nonetheless impair quality of life.

Preoperative somatostatin analogues versus direct transsphenoidal surgery for newly-diagnosed acromegaly patients: a systematic review and meta-analysis using the GRADE system

Whether the preoperative use of somatostatin analogues (SA) improves surgical outcomes in acromegaly is still a matter of debate.

OBJECTIVE

We conducted a systematic review of randomized, controlled trials that compared the short-term outcomes of preoperative use of SA (Pre-SA) with direct TSS (No-SA) for the treatment of newly diagnosed acromegaly.

METHODS

Embase, Pubmed, Lilacs, and Central Cochrane were used as our data sources. The primary outcomes were no need for any adjuvant treatment 3 months after surgery, based on biochemical results (GH nadir after OGTT <1 μg/L and normal IGF-1 for age and gender), quality of life and mortality. The included trials were analyzed using the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

A total of 2.099 references were identified and two reviewers independently screened the titles and abstracts. From the 14 potentially eligible studies, four were included and ten were excluded due to lack of randomization or different outcomes. A pool of 261 patients was randomly assigned to Pre-SA or No-SA. Meta-analysis of IGF1 normalization showed a significant difference in favor of Pre-SA (RR 2.47; 95% CI 1.66, 3.77). Adding a GH nadir on OGTT ≤1 μg/L, we found a RR of 2.15 (95% CI 1.39, 3.33). Quality of evidence for no need of adjuvant postoperative treatment was moderate, but for improving quality of life was very low and for mortality was absent.

CONCLUSION

Pre-SA increases the chance of biochemical control of acromegaly 3 months after TSS in patients harboring GH-secreting pituitary macroadenomas.

Should all patients with acromegaly receive somatostatin analogue therapy before surgery and, if so, for how long?

Current guidelines do not recommend the routine use of somatostatin analogue pretreatment prior to surgery in patients with growth hormone-secreting pituitary tumours. In theory, presurgical use of somatostatin analogues should improve metabolic control and reduce soft tissue swelling, leading to improved anaesthetic outcomes. Shrinkage of tumours prior to surgery might also improve surgical remission rates. Hence, this article addresses the question: Should all patients with acromegaly receive a somatostatin analogue prior to surgery? Clinical trials published before December 2013 were reviewed, although literature in this area remains relatively deficient. We conclude: (i) On the basis of limited data available, somatostatin analogue pretreatment does not improve anaesthetic or immediate postoperative outcomes (i.e. hospital stay, rates of surgical complications and postoperative pituitary dysfunction). (ii) Somatostatin analogues should be considered in all patients with growth hormone-secreting macroadenomas, including invasive macroadenomas, when the overall surgical remission rate for macroadenomas at the treating centre is below 50%. Four recent RCTs have demonstrated increased rates of surgical remission using such an approach. (iii) When deemed appropriate, patients should be treated with somatostatin analogues for at least 3 months before surgery; there is currently no evidence that treatment beyond 6 months provides any additional benefit. Patients with minimally invasive macroadenomas are those most likely to benefit in terms of improved surgical remission.

Meta-analysis on the effects of octreotide on tumor mass in acromegaly

BACKGROUND

The long-acting somatostatin analogue octreotide is used either as an adjuvant or primary therapy to lower growth hormone (GH) levels in patients with acromegaly and may also induce pituitary tumor shrinkage.

OBJECTIVE

We performed a meta-analysis to accurately assess the effect of octreotide on pituitary tumor shrinkage.

DATA SOURCES

A computerized Medline and Embase search was undertaken to identify potentially eligible studies.

STUDY ELIGIBILITY CRITERIA

Eligibility criteria included treatment with octreotide, availability of numerical metrics on tumor shrinkage and clear definition of a clinically relevant reduction in tumor size. Primary endpoints included the proportion of patients with tumor shrinkage and mean percentage reduction in tumor volume.

DATA EXTRACTION AND ANALYSIS

The electronic search identified 2202 articles. Of these, 41 studies fulfilling the eligibility criteria were selected for data extraction and analysis. In total, 1685 patients were included, ranging from 6 to 189 patients per trial. For the analysis of the effect of octreotide on pituitary tumor shrinkage a random effect model was used to account for differences in both effect size and sampling error.

RESULTS

Octreotide was shown to induce tumor shrinkage in 53.0% [95% CI: 45.0%-61.0%] of treated patients. In patients treated with the LAR formulation of octreotide, this increased to 66.0%, [95% CI: 57.0%-74.0%). In the nine studies in which tumor shrinkage was quantified, the overall weighted mean percentage reduction in tumor size was 37.4% [95% CI: 22.4%-52.4%], rising to 50.6% [95% CI: 42.7%-58.4%] with octreotide LAR.

LIMITATIONS

Most trials examined were open-label and had no control group.

CONCLUSIONS

Octreotide LAR induces clinically relevant tumor shrinkage in more than half of patients with acromegaly.

[Treatment of acromegaly: a critical analysis of the last ten years]

The ten previous years in terms of acromegaly treatment were essentially characterized by the experience accumulated with new formulations of somatostatin analogues or new drugs such GH-receptor antagonists recently available. Surgery remains the first-line treatment and its results did not change despite the generalization of endoscopy, which mainly seems to decrease local side-effects. The setting of radiotherapy was essentially modified by the increasing use of gamma-knife or stereotactic radiotherapy; however, their results are essentially the same as the classic fractionated, conventional radiotherapy and nobody knows if it will decrease the side-effects of this therapeutic modality. Nevertheless, thanks to a multistep therapeutic strategy, combining the different therapeutic modalities, it has become very rare for acromegaly not to be controlled in a patient.

Resistance to somatostatin analogs in acromegaly

Somatostatin analogs (SA) are widely used in acromegaly, either as first-line or adjuvant treatment after surgery. First-line treatment with these drugs is generally used in the patients with macroadenomas or in those with clinical conditions so severe as to prevent unsafe reactions during anesthesia. Generally, the response to SA takes into account both control of GH and IGF-I excess, with consequent improvement of clinical symptoms directly related to GH and IGF-I excess, and tumor shrinkage. This latter effect is more prominent in the patients treated first-line and bearing large macroadenomas, but it is also observed in patients with microadenomas, even with little clinical implication. Predictors of response are patients' gender, age, initial GH and IGF-I levels, and tumor mass, as well as adequate expression of somatostatin receptor types 2 and 5, those with the highest affinity for octreotide and lanreotide. Only sporadic cases of somatostatin receptor gene mutation or impaired signaling pathways have been described in GH-secreting tumors so far. The response to SA also depends on treatment duration and dosage of the drug used, so that a definition of resistance based on short-term treatments using low doses of long-acting SA is limited. Current data suggest that response to these drugs is better analyzed taking together biochemical and tumoral effects because only the absence of both responses might be considered as a poor response or resistance. This latter evidence seems to occur in 25% of treated patients after 12 months of currently available long-acting SA.

Growth hormone-secreting adenomas: pathology and cell biology

The majority of patients with acromegaly harbor a functioning growth hormone (GH) pituitary adenoma. Growth hormone–secreting adenomas correspond to about 20% of all pituitary adenomas. From the histopathological point of view, a variety of adenomas may present with clinical signs and symptoms of GH hypersecretion including pure GH cell adenomas (densely and sparsely granulated GH adenomas), mixed GH and prolactin cell adenomas, and monomorphous adenomas with primitive cells able to secrete GH and prolactin including the acidophilic stem cell adenoma and the mammosomatotroph cell adenoma. In this article, the author reviews the main pathological features of the GH-secreting adenomas and some of the molecular genetics mechanisms involved in their pathogenesis.

Rab3B immunoexpression in human pituitary adenomas

Rab3B, a member of the Rab family is a low molecular weight GTP-binding protein that has been implicated in the regulation of exocytosis. To shed light on its presence in the normal human pituitary and in adenomas, a detailed immunohistochemical study of 130 surgically removed human pituitary adenomas was undertaken, including 23 somatotroph, 32 lactotroph, 19 functional corticotroph, 10 silent subtype 1 and 8 silent subtype 2 corticotroph adenomas, 12 gonadotroph hormone producing, 10 thyrotroph, 7 silent subtype 3 adenomas, and 9 null cell adenomas, 5 of the latter being of oncocytic type. Among the 32 prolactin lactotroph adenomas, 10 had been treated preoperatively with bromocriptine, a dopamine agonist. Among the 23 somatotroph adenomas, 10 were pretreated with octreotide, a long acting somatostatin analog. In addition, 10 nontumorous adenohypophyses were also examined. As used by the World Health Organization, the tumors were classified on the basis of their histologic, immunohistochemical, and ultrastructural characteristics. The results showed Rab3B immunopositivity to be strongest in corticotroph adenomas followed by thyrotroph, lactotroph, gonadotroph, null cell, and somatotroph adenomas. No difference was noted between endocrinologically active and silent corticotroph adenomas. Bromocriptine therapy was associated with decreased Rab3B immunoexpression, whereas pretreatment with octreotide induced no significant reduction. Immunopositivity was cytoplasmic and was evenly distributed. No staining was noted in normal adenohypophyses. Our results add new information to the view that Rab3B is involved in the regulation of pituitary hormone secretion.

Growth hormone-secreting tumor shrinkage after 3 months of octreotide-long-acting release therapy predicts the response at 12 months

OBJECTIVE

The objective of the study was to evaluate whether tumor shrinkage or GH and IGF-I levels achieved after 3 months predicted tumor shrinkage after 12 months of octreotide-long-acting release (LAR) treatment.

PATIENTS

Patients included 67 patients with de novo acromegaly (33 women, 34 men; aged 20-82 yr) receiving LAR at a dose of 20 mg every 28 d for 3 months. Final LAR dose was 10 mg every 28 d in 4, 30 mg every 28 d in 39, 20 mg every 28 d in 24 patients.

DESIGN

The design of the study was analytical, observational, open, and retrospective.

OUTCOME MEASURES

Percent change in GH and IGF-I levels and tumor volume after 3 and 12 months of therapy was measured. Stepwise regression and receiving-operator characteristics analysis were used to calculate the optimal cutoff to predict 12 months tumor shrinkage at 12 months.

RESULTS

The percent tumor shrinkage after 12 months was significantly correlated with GH, IGF-I, and tumor volume at 3 months and with the dose of LAR administered between 3 and 12 months. There was no correlation with gender, age, baseline GH levels and tumor volume. In a stepwise regression analysis, percent tumor shrinkage after 3 months was the best predictor of tumor shrinkage after 12 months (t = 5.92; P < 0.0001), followed by GH levels after 3 months (t = 2.86; P = 0.0056). To predict 50% or greater tumor shrinkage after 12 months, the best cutoff point of tumor shrinkage at 3 months was 22.1% [sensitivity (95% confidence interval) = 85.5% (71.2-95.4); specificity = 83.3% (65.3-94.3)], whereas that of GH levels after 3 months was 7.8 microg/liter [sensitivity = 70.3% (53.0-84.1); specificity = 93.3% (79.0-99.0)].

CONCLUSION

Tumor shrinkage achieved after 3 months of LAR treatment at 20 mg/28 d predicted tumor shrinkage at 12 months, provided that dosages were changed according to individual patients requirement.

Short-term preoperative octreotide treatment of GH-secreting pituitary adenoma: predictors of tumor shrinkage

We reviewed the cases of 32 patients with growth hormone (GH)-secreting macroadenoma who underwent short-term octreotide treatment before transsphenoidal surgery to determine which types of adenoma the preoperative treatment were sensitive and whether predictors of tumor shrinkage could be identified. The effects of preoperative octreotide treatment, endocrinologic effect and effect on tumor volume in 32 patients were evaluated retrospectively in relation to tumor features on magnetic resonance images and responses to endocrinologic challenge tests. At a daily dose of 300 microg for 2-3 weeks, octreotide reduced serum GH and insulin-like growth factor-1 (IGF-1) levels to 31.9 % and 51.6% of pretreatment values, respectively, and led to a mean tumor volume of 68% of pretreatment volume in 52% of the patients. The endocrinologic effect and the effect on tumor volume were larger in Knosp grades 0-2 than in Knosp grades 3-4. Tumor shrinkage occurred significantly more often among patients that had a good response to both octreotide and bromocriptine challenge tests. For surgical removal of the tumor, the effect of reducing tumor to 68% of pretreatment volume will be beneficial for the macroadenomas of Knosp grades 1-2. Preoperative short-term octreotide treatment is effective for GH-secreting macroadeomas of Knosp grades 1-2 and a good response to both octreotide and bromocriptine challenge tests is a predictor of subsequent tumor shrinkage. These results will lead to more effective selection of patients for preoperative octreotide treatment.

Long-term Primary Medical Therapy with Somatostatin Analogs in Acromegaly

To cure acromegalic patients, transsphenoidal surgery is considered first, especially for microadenoma. However, less than 50% of patients with macroadenoma achieve satisfactory biochemical control. Moreover, surgery may cause hypopituitarism. Medical therapy may offer the prospect of near normalization of growth hormone (GH)/insulin-like growth factor-1 levels with substantial tumor shrinkage in a significant number of patients. Here, we report two cases of acromegaly under treatment with somatostatin analogs alone for more than 10 years. Case 1 was a 54-year-old man with a pituitary macroadenoma. He received 4 years of octreotide treatment followed by 6 years of prolonged-release (PR) lanreotide resulting in normal GH level. Case 2 was a 60-year-old woman with a 1.3 cm pituitary tumor. She received 8 years of octreotide treatment followed by 6 years of PR lanreotide resulting in subnormal GH level and gallbladder sludge. She had received bilateral total hip replacement for hip osteoarthritis at the age of 59 years. These cases illustrate that long-term treatment with somatostatin analogs offers an alternative choice in selected acromegalic patients, such as those with pituitary tumor who cannot be cured by surgery, those who have unacceptable anesthetic risk and those who refuse surgery.

Transsphenoidal microsurgery for newly diagnosed acromegaly: a personal view after more than 1,000 operations

The aim of this short review is to inform about the possibilities and limits of transnasal microsurgery in acromegaly. The current reports on surgical remissions, according to the strict criteria with international consensus using age- and sex-related normal levels for insulin-like growth factor-I and suppression of growth hormone (GH) with oral glucose tolerance below 1 mug/l, are more or less agreeable with values between 34 and 74%. In microadenomas (<10 mm in diameter), 59-95% remissions are published. Some improvement might be achieved in macroadenomas which presently have a chance of 26-68% to be satisfactorily operated on. Special instruments introduced by us to visualize and remove partially invasive adenoma parts are described. Intraoperative magnetic resonance imaging is discussed. With intraoperative measurement of GH, small adenoma rests <3 mm can be diagnosed. When GH did not sufficiently decline, an additional tumor search resulted in a significant improvement in results in resectable macroadenomas. With these techniques, we achieved remission rates which can hardly be further increased (micros 95%, macros 68%). In grossly invasive grade 4 adenomas, which are frequent in our unit, only an 80-95% reduction in tumor mass is feasible. Preoperative treatment with somatostatin analogues as used in most of our patients reduces the comorbidity and facilitates adenoma removal which is still controversially discussed in the literature. The complication rate of microsurgery in experienced hands is low.

Effects of medical therapy on pituitary tumors

Previously surgery and irradiation were the only available procedures to treat patients with pituitary tumors. During the last few decades, novel drugs such as dopamine agonists and long-acting somatostatin analogs were developed and, an alternative medical therapy emerged. This paper summarizes the effect of medical therapy on the morphologic features of pituitary tumors and illustrates the ultrastructural alterations on electron micrographs. Currently drugs can be used in the management of pituitary tumors secreting GH, PRL, and/or TSH in excess. No medical therapy is available so far for ACTH-, FSH-, LH-, or alpha-subunit-secreting tumors as well as non-hormone-secreting pituitary tumors. Dopamine agonists are effective in the management of PRL-secreting tumors; they cause marked reversible tumor shrinkage in the substantial majority of patients. Long-acting somatostatin analogs are useful in the management of GH- and TSH-secreting pituitary tumors; they lead to mild to moderate tumor shrinkage in approximately 50% of cases. In patients treated with these drugs reduction of elevated blood hormone levels and amelioration of clinical symptoms ensue. It should be emphasized that no permanent cure is obtained. Blood hormone levels increase and the clinical symptoms reappear after discontinuation of treatment. Recently GH receptor blockers (pegvisomant) were introduced in the treatment of GH-producing pituitary adenomas. To the authors' knowledge the effect of these drugs on the morphology of pituitary tumors has not been revealed so far.

Somatostatin analogs as primary medical therapy for acromegaly

Acromegaly is a debilitating disease usually caused by a growth-hormone secreting pituitary adenoma. Therapeutic goals include improvement of symptoms, reduction in tumor mass, biochemical normalization, and preservation of pituitary function. Treatment options include transsphenoidal surgery, radiation, and pharmacotherapy. In view of the good cure rate, surgery remains the therapeutic modality of choice for most patients with microadenomas or well-circumscribed macroadenomas. In contrast, >40% of patients with invasive macroadenomas (who make up the majority of patients with acromegaly) will have residual disease following surgery, and require additional therapeutic intervention. Somatostatin analogs result in biochemical normalization in >60% of non-operated patients, and are well tolerated. Therefore, somatostatin analogs have emerged as a rational first-line treatment for the appropriately selected patient with acromegaly.

Modern treatment of acromegaly

Acromegaly is an endocrine disorder characterised by increased morbidity and mortality. It is usually caused by a growth hormone secreting pituitary adenoma and is manifested by a variety of clinical features. Surgery is usually the treatment of choice, however over the last few years, several new methods of treatment have been developed. A recent consensus on the targets for treatment has led to multiple studies being conducted to assess the efficacy of the currently available options. This review examines the evidence for and against these treatments.

Thyrotropin-secreting pituitary adenomas. Clinical and biological heterogeneity and current treatment

Thyrotropin (TSH)-secreting pituitary adenomas represent about 1-2% of all pituitary adenomas and cause secondary or central hyperthyroidism. TSH-secreting adenomas are part of the syndrome of 'inappropriate secretion of TSH' (SITSH). The hormonal profile is characterized by nonsuppressed TSH in the presence of high levels of free thyroid hormones (FT3 and FT4). Previous reports have described the surgical cure of TSH adenoma to be more difficult than other functional adenomas because of large and invasive features. However, with the current introduction of ultrasensitive immunometric assays, TSH-secreting adenomas are more often recognized. Early diagnosis of TSH-secreting adenomas leads to a high rate of remission of hyperthyroidism after surgery. However, some of those type of adenomas have clinical heterogeneity, and subsequently cannot be cured by surgery alone. We present our experiences and review reported cases of TSH-secreting adenomas to direct current management.

Long-term surgical outcome in 16 patients with thyrotropin pituitary adenoma

OBJECT

Thyrotropin-secreting pituitary adenomas are rare lesions of the endocrinological system. Although introduction of a hypersensitive radioimmunoassay for thyrotropin enables the recognition of inappropriate secretion of this hormone, the aforementioned lesions remain uncommon and unfamiliar to most neurosurgeons. It has been reported previously that surgical cure of thyrotropin-secreting adenomas is more difficult than in other functional adenomas because of the large size and invasive features of the former. However, the long-term outcome after surgery has not been well documented. The authors report on a surgical series of 16 patients with thyrotropin adenoma and the results of long-term follow up.

METHODS

Sixteen patients ages 23 to 62 years (12 women and four men) underwent transsphenoidal removal of thyrotropin adenomas between 1983 and 1999. These patients had the syndrome of inappropriate thyrotropin secretion (SITS) with pituitary mass lesions. Four of the patients had undergone previous subtotal thyroidectomy and/or radioiodine thyroid ablation, and 11 had been treated with antithyroid medication. Radiological investigations demonstrated macroadenomas in 14 patients, and 10 of those had cavernous sinus invasion. Surgical findings showed unusually fibrous and firm tumors in 13 (81.2%) of 16 patients. Preoperative octreotide administration was revealed to be effective for serum thyrotropin reduction as well as tumor shrinkage. Transsphenoidal surgery was performed with no morbidity resulting. Surgical remission was achieved in 10 (62.5%) of 16 patients, and total remission was achieved in 14 patients (87.5%) with a combination of additional radiation or medical therapy. In the other two patients, SITS persisted because of tumor rests in the cavernous sinus. Therefore, radiation and/or antithyroid therapy was administered. In the mean follow-up period of 7.5 years (range 11 months-15.8 years), no recurrence of tumor was observed on magnetic resonance images, whereas recurrence of SITS was found in two patients with no tumor regrowth. In addition, coexistent primary hyperthyroidism was found in two other patients despite remission of SITS after surgery.

CONCLUSIONS

Transsphenoidal surgery can achieve a good long-term outcome in patients with thyrotropin-secreting pituitary adenomas if surgery is performed before these become larger, invasive tumors. In the authors' experience, thyrotropin-secreting adenomas are fibrous and firm, which makes it difficult to achieve surgical remission. In addition, even satisfactory resection of the tumor sometimes results in recurrence of SITS or hyperthyroid symptoms due to coexistent primary hyperthyroidism. It is emphasized that a careful follow-up review is necessary after surgery, especially in patients with a long preoperative history of hyperthyroidism.

Pharmacotherapy or surgery as primary treatment for acromegaly?

In recent years important progress has been made in the management of acromegaly due to the availability of effective and well tolerated drugs and to improved surgical techniques, resulting in a broader choice of therapeutic interventions. Although surgery in the hands of an experienced surgeon still represents the primary option for the majority of patients, the new formulations of somatostatin analogues and dopamine agonists have partially modified the primary therapeutic approach to this severe and disabling chronic disease. Therapy with somatostatin analogues has been shown to reduce morbidity and the mortality rate in patients with acromegaly, and currently in some patients this medical approach may be preferable to surgery. Although in selected patients individualised pharmacotherapy might represent the primary therapy, trans-sphenoidal surgery of microadenomas and noninvasive macroadenomas remains the primary option, since the remission rate is very high and the costs are relatively low in comparison with lifelong therapy with somatostatin analogues. However, the treatment schedule in acromegaly should consider criteria additional to tumour size and invasiveness, such as the age and the general clinical condition of the patient. Presurgical treatment with somatostatin analogues has been reported to reduce surgical complications and time of hospitalisation after the operation. Moreover, a multidisciplinary team of well trained specialists is needed in order to guarantee the most optimal quality of life and life expectancy for patients with acromegaly.

Short-term pre-surgical treatment with somatostatin analogues, octreotide and lanreotide, in acromegaly

Eighteen patients with symptoms of active acromegaly were treated with somatostatin analogues for 4 weeks before surgery. Both before and after the treatment, levels of growth hormone (GH), prolactin (PRL), insulin growth factor -I (IGF-I), luteotropin (LH), folliculostimulin (FSH) and subunit alpha of glycoprotein hormones were estimated. Glucose tolerance test, magnetic resonance imaging (MRI) examination, sight acuity and field of vision tests were also performed. The same tests were performed on ten control patients with clinically and biochemically active acromegaly, subjected to surgery but not treated with somatostatin analogues. In six patients treated with somatostatin analogues GH levels decreased significantly to less than 5 ng/ml and in two patients remained elevated while in 10 patients GH level decreased and ranged from 6.1 to 42.9 ng/ml. In 13 patients we observed a decrease in IGF-I to normal levels (<400 ng/dl) and in 3 patients we noted a decrease to levels slightly higher than normal. There was also a slight decrease in alpha subunit concentration. In the glucose inhibition test 4 patients demonstrated normalized GH levels. In patients with elevated PRL and TSH levels, treatment with somatostatin analogues induced their decrease. No changes were observed in levels of LH and FSH. After therapy MRI examination disclosed a decrease in tumor volume in two patients (by 20 and 25%, respectively) and no changes in tumor size in 16 patients. The two patients with a decreased tumor volume also showed normalized glucose tolerance tests. All patients manifested an improved clinical condition. Neurosurgeons disclosed a decreased tumor consistency which greatly facilitated surgical procedure. Our studies documented favourable effects of somatostatin analogues on the assayed hormone levels, and on the general condition of the patients as well as on the course of the surgical procedure itself.

Medical therapy for acromegaly

Both somatostatin analogues, which bind to the somatostatin receptor subtypes 2 and 5, and dopamine agonists, which are specific for the D2 receptor, have been used to treat acromegaly. Each of these classes of drugs contains several compounds that vary in duration of action, efficacy, and side effect profile. Although somatostatin analogues reduce GH levels and alleviate symptoms in most patients and restore IGF-1 levels to normal in 60% to 65% of patients, tumor shrinkage is limited to 40% of patients. evidence in the literature supports the use of these medications as secondary therapy in patients with acromegaly who have had surgery and who continue to have elevated GH levels (above 2 ng/mL during an oral glucose tolerance test) with or without IGF-1 concentrations that are above the upper limit of normal for age. In addition, medical therapy indicated in patients who refuse surgery and in patients who are poor surgical candidates. The controversial question is whether medical therapy should be an option for primary treatment of the acromegalic patient. Currently, ther are no data from prospective randomized trials comparing the effects of surgery versus somatostatin analogues as first-line therapy for for newly diagnosed acromegalic patients. Limited data from nonrandomized studies demonstrate that somatostatin analogues are effective long-term in suppressing GH and reducing IGF-1 into the normal range in approximately two-thirds of patients who have never undergone previous treatment. It is still the consensus that patients with GH-secreting microadenomas should undergo surgical resection, because the likelihood of complete cure by an experience neurosurgeon is high, at least 70% or greater. Successful surgical treatment has the advantage of completely removing the tumor in contrast to medical therapy, which rarely produces shrinkage greater than 50% despite the fact that IGF-1 and GH levels may be normal. In patients with macroadenomas of a size and location that suggest that the chance of complete resection is 40% or less, primary treatment with a somatostatin analogue should be considered as one option in the initial management of the patient. Another option in such an individual would be surgical debulking followed by medical therapy, because it is theoretically possible that biochemical cure with medical therapy after surgical debulking might be achieved with lower doses. The cost-effectiveness of these approaches has not yet been determined. Once the decision has been made to begin medical therapy, a choice must be made between dopamine agonists and somatostatin analogues. Most evidence suggests that somatostatin analogues are more effective than dopamine agonists and therefore would be the therapy of choice. In select patients, dopamine agonists, particularly the long-acting agonist cabergoline, may be preferred initially if the patient is unwilling to take injections or if the GH elevations are relatively modest (< 10 ng/mL). Biochemical cure should be assessed by measurement of GH (which can be performed 2 hours after an octreotide injection) and IGF-1 concentrations. The goal of treatment include reduction of of GH below 2 ng/mL and reduction of IGF-1 into the normal range. In patients who do not reach these goals, the dose or frequency of injection of the somatostatin analogue or both should be increased. If such measures are unsuccessful, a dopamine agonist may be added to the medical regimen because some studies suggest that combination therapy may be more effective in select cases than octreotide therapy alone. If such measures are still unsuccessful, other options should be considered, including surgery, pituitary radiation, and medical treatment with investigational drugs.

Recent primary transnasal surgical outcomes associated with intraoperative growth hormone measurement in acromegaly

OBJECTIVE

Since 1983, we have measured GH intraoperatively to improve the surgical outcome for acromegalic patients with GH secreting pituitary adenomas. Here, we present the recent results of primary surgery in patients with acromegaly to examine the effect of improved surgical techniques and experience. PATIENTS AND MEASUREMENT: Intraoperative GH concentrations were measured in 78 consecutive acromegalic patients who had not previously undergone surgery between May 1992 and April 1994 (45 females and 33 males, age range, 21-70 years, mean, 47.1 +/- 1.3). All patients were followed for at least 3 years. Direct transnasal tumour extirpation was performed. Intraoperative GH measurements were assayed 0, 20 and 60 min after tumour removal. A plasma GH level < or = 4.5 micrograms/l at 60 min after initial tumour removal was used as a criterion of radical tumour removal. In cases with intraoperative plasma GH concentrations > or = 40 micrograms/l prior to tumour resection, the half-life of the GH concentration at 20 min was used to assess completeness of tumour removal. In these cases, it was defined as having achieved a 50% reduction in plasma GH at 20 min compared to 0 min after tumour resection. To obtain intraoperative GH measurements, mild anaesthesia was continued for an average of 82 +/- 23 min.

RESULTS

Radical tumour removal was determined intraoperatively in 51 patients and subsequently confirmed in 50 patients (98.0%). In 18 of 27 patients with incomplete tumour removal, immediate reoperation was performed under continous anaesthesia. In 11 of these 18 patients, endocrinological remission was achieved (14.1%; 11/78). None of the remaining nine patients who did not undergo secondary surgery achieved remission. Secondary surgery improved the remission rate from 85.7% (12/14) to 92.9% (13/14) in microadenomas and from 70.1% (38/54) to 88.9% (48/54) in non-invasive macroadenomas. Remission was not observed in patients with imageproven extrasellar extension.

CONCLUSIONS

Secondary surgery based on intraoperative GH measurement improves the outcome of tumour resection in patients with non-invasive GH secreting macroadenomas.

Visual improvement during octreotide therapy in a case of episellar meningioma

Meningiomas of the tuberculum sellae can induce compression of the optic tract. We report the case of a 54-year-old female patient affected by a suspected pituitary macroadenoma with severe visual field defects, who experienced a significant clinical and visual improvement during short-term octreotide therapy, contrasting with the lack of neuroradiological evidence for tumor shrinkage. The patient subsequently underwent transcranial surgery with a final diagnosis of meningioma. The putative mechanisms of visual improvement during octreotide therapy are discussed.

Absence of apoptosis in somatotropinomas treated with octreotide

Octreotide is a potent agonist of somatostatin that lowers the serum level of growth hormone (GH), and reduces the size of somatotropinomas. However, the detailed mechanism of shrinkage of this tumour is not known. We, therefore, evaluated 11 patients with somatotropinomas who were treated with octreotide 300 micrograms/day for 2-5 weeks to observe the morphological changes in the tumour using electron microscopy and the immunocytochemical study of apoptosis using polyclonal anti-single stranded DNA. Findings were compared with those obtained with bromocriptine treatment (10 mg/day, 2 weeks) of 5 patients with somatotropinomas, and 11 patients who received no preoperative treatment (control group). The octreotide group showed neither increase in stromal tissue nor cell death. The size of tumour cells appeared to be slightly reduced. No typical apoptotic bodies were seen on the electron micrographs. The apoptotic index in the octreotide group (0.40 +/- 0.60%; mean +/- SD) resembled that in the control group (0.81 +/- 0.79%). In contrast, the bromocriptine group showed some cell death and an increase in stromal tissue. The bromocriptine group also showed the apoptotic index which (20.1 +/- 14.8%) was significantly higher than that of the control group (0.81 +/- 0.79%). Thus, octreotide did not induce apoptosis in somatotropinomas despite the presence of tumour shrinkage. Because of the lack of fibrosis observed in the octreotide-treated tumours, the preoperative administration of octreotide may help to improve the outcome of the transsphenoidal operation.

Presurgical Octreotide: treatment in acromegaly

One hundred seventy-two acromegalics who were operated on using the trans-sphenoidal approach underwent long-term follow-up evaluation. Sixty-four received 100 micrograms octreotide subcutaneously three times daily: for 3 to 6 weeks before surgery in 14 patients (group 1); and for 3 to 9 months in 41 and for 13 to 39 months in nine (n = 50, group 2). In 18 group 2 patients, the dose was increased stepwise to 500 micrograms three times daily because of incomplete suppression of growth hormone (GH)/insulin-like growth factor-1 (IGF-1). Tumor shrinkage was seen in 60% within 3 weeks, being nearly maximal by 3 to 4 months. More group 2 patients had greater than 25% tumor shrinkage (14 of 48 v 1 of 14 in group 1). Clinical response was excellent or good in 89%. Decrease in soft-tissue swelling and weight loss, and improved vitality, performance, carbohydrate metabolism, and cardiovascular function, facilitated anesthetic and surgical management; tumor removal was easy in virtually all cases. In all 64 patients, GH levels decreased by > or = 50%, and to < 2 micrograms/L in three of 14 patients initially and 25 of 50 patients after more prolonged treatment. IGF-1 levels decreased to normal in seven of 14 group 1 and 31 of 50 group 2 patients. Light and electron microscopy showed that adenomatous tissue exposed to octreotide had lysosomal accumulation, amyloid deposition, mild to moderate perivascular fibrosis, and moderate size reduction in both cytoplasmic and nuclear areas, with virtually no cellular complications. Remission with enclosed adenomas was greater (p < .05) than for the 108 patients not treated with octreotide; there was no difference for invasive adenomas. Octreotide use for 3 to 4 months before surgery can be recommended.

Clinical features and differential diagnosis of pituitary tumours with emphasis on acromegaly

Pituitary adenomas are frequently encountered, benign intracranial tumours. Clinically classified according to their capacity to produce and secrete hormones, pituitary tumours are diagnosed from the clinical manifestations and biochemical findings of specific pituitary hormone overproduction or of impaired pituitary function due to pressure on normal pituitary cells, the pituitary stalk or the hypothalamus. Additionally, the tumour may result in neurological manifestations due to its effect as an intracranial space-occupying lesion. Pituitary adenomas may present acutely with pituitary apoplexy after intrapituitary haemorrhage or infarction. The subsequent hypofunction of the pituitary with concomitant neurological sequelae of an expanding intracranial mass are often associated with excruciating headache, diplopia and visual field defects. Gradually developing neurological deficits or secondary endocrine failure over several years may precede the recognition of non-secretory tumours (30-40% of pituitary adenomas) as well as some of the hormone-producing adenomas, especially when they expand beyond the confines of the sella turcica. Asymptomatic masses occur in the pituitary in 5-27% of unselected autopsy series. About 10-20% of pituitaries imaged as part of a brain study contain lesions 'consistent with a pituitary adenoma', with about half being pituitary adenomas ('incidentalomas'). Many advocate screening such cases for a wide spectrum of pituitary function abnormalities. Clinical judgement should be utilized to determine the extent of the work-up and the frequency of follow-up. Acromegaly, a clinical syndrome caused by excess growth hormone secretion, accounts for one-sixth of resected pituitary tumours. This disorder leads to chronic progressive disability and a shortened life span, with approximately 50% of untreated acromegalic patients experiencing premature death. The prevalence of acromegaly has been estimated to range from 50 to 70 per million, with the age of diagnosis usually between the third and fifth decades. Conditions associated with acromegaly include glucose intolerance, diabetes mellitus, lipid abnormalities, cholelithiasis, goitre, and hyperthyroidism, respiratory complications, hypertension, cardiovascular disease, and calcium metabolism abnormalities. An association between acromegaly and cancer, especially of the colon, is now recognized. Epidemiological series have indicated that cancer of the colon, breast and other types of malignancy are a cause of death with increased frequency in acromegalics compared with expected rates. Hypopituitary symptoms secondary to the mass effect of macroadenomas in acromegalic patients are common. Among premenopausal women, menstrual irregularities and galactorrhoea have been reported in 40-70%, while more than half of the men complain of impotence and decreased libido.(ABSTRACT TRUNCATED AT 400 WORDS)