Conventional pituitary irradiation is effective in normalising plasma IGF-I in patients with acromegaly

HIGH-PRECISION CONFORMAL FRACTIONATED RADIOTHERAPY IS EFFECTIVE IN ACHIEVING REMISSION IN PATIENTS WITH ACROMEGALY AFTER FAILED TRANSSPHENOIDAL SURGERY

OBJECTIVE

Variable efficacy of pituitary radiotherapy in acromegaly is reported. Here we sought to assess the efficacy of high-precision conformal fractionated radiotherapy (CRT) in patients with acromegaly after failed TSS.

METHODS

A retrospective analysis was conducted a in tertiary care referral center between 1999 to 2013 on 36 acromegaly patients (M: 16, F: 20; median age: 36.0 years) with macroadenoma and mean growth hormone (GH) and insulin-like growth factor-1 (IGF1) upper limits of normal (ULN) of 15.9 ± 14.3 ng/mL and 1.74 ± 0.43, respectively. The cohort was divided into 2 groups: 30 patients (M: 13, F: 17) who were medical treatment naïve, and 6 patients (M: 3, F: 3) who received medical treatment after CRT.

RESULTS

Normalization of GH (fasting GH <1 ng/mL), normalization of IGF1 (ULN <1), and remission (normalization of GH and IGF1) were achieved in 20 (55%), 23 (63%) and 20 (55%) patients, respectively. The mean time required to achieve remission was 63 ± 33.4 months. Follow-up duration was the only predictor of achieving remission. GH level declined exponentially by 65% and 89% at 2 and 5 years, respectively. New onset hypopituitarism was noted in 33% of patients. Tumor control was achieved in 100% of patients. In groups 1 and 2, 18 (60%) and 2 (33.3%) achieved remission post-CRT, and the mean times required to achieve remission were 58.6 ± 30.7 months and 102 ± 42.4 months, respectively.

CONCLUSION

High-precision CRT is an effective modality to achieve remission in patients with acromegaly after failed TSS.

Results of gamma knife radiosurgery in acromegaly

Objective. Single-session radiosurgery with Gamma Knife (GK) may be a potential adjuvant treatment in acromegaly. We analyzed the safety and efficacy of GK in patients who had previously received maximal surgical debulking at our hospital. Methods. The study was a retrospective analysis of hormonal, radiological, and ophthalmologic data collected in a predefined protocol from 1994 to 2009. The mean age at treatment was 42.3 years (range 22-67 yy). 103 acromegalic patients participated in the study. The median follow-up was 71 months (IQ range 43-107). All patients were treated with GK for residual or recurrent GH-secreting adenoma. Results. Sixty-three patients (61.2%) reached the main outcome of the study. The rate of remission was 58.3% at 5 years (95% CI 47.6-69.0%). Other 15 patients (14.6%) were in remission after GK while on treatment with somatostatin analogues. No serious side effects occurred after GK. Eight patients (7.8%) experienced a new deficit of pituitary function. New cases of hypogonadism, hypothyroidism, and hypoadrenalism occurred in 4 of 77 patients (5.2%), 3 of 95 patients (3.2%), and 6 of 100 patients at risk (6.0%), respectively. Conclusion. In a highly selected group of acromegalic patients, GK treatment had good efficacy and safety.

Gammaknife radiosurgery in patients with acromegaly

We aimed to evaluate the efficacy and reliability of gamma-knife radiosurgery (GKR) in 22 patients with acromegaly at the Endocrinology-Metabolism Clinic of Cerrahpasa Medical School. We collected data retrospectively from hospital records on disease activity and other pituitary functions, pituitary MRI and visual fields, before GKR and 6, 12, 24, 36, 48 and 60 months after GKR. The median follow-up duration after GKR was 60 months (interquartile range [IQR]: 24-60 months). The remission rate was 54.5% after the 60 months of follow-up. The median growth hormone (GH) level at 60 months after GKR (0.99 ng/mL [IQR: 0.36-2.2]) was significantly lower than the median GH level before GKR (5.65 ng/mL [IQR: 3.85-7.2] (p=0.002). The median insulin-like growth factor-1 (IGF-1) level 60 months after GKR (221.5 ng/mL [IQR: 149-535]) was significantly lower than the median IGF-1 level before GKR (582.5 ng/mL [IQR: 515-655]) (p=0.008). Tumour growth was well controlled in 20 patients (95.2%). Six patients (28.6%) developed new-onset hypopituitarism. We concluded that GKR is an effective adjuvant treatment to control tumour growth, lower GH and IGF-1 levels, and to increase remission rates in patients with acromegaly who were refractory to surgical and medical treatment.

Fractionated stereotactic radiotherapy in patients with acromegaly: an interim single-centre audit

AIM

To evaluate the effect of fractionated stereotactic radiotherapy (FSRT) in acromegaly in a retrospective analysis.

PATIENTS AND METHODS

Thirty-four patients (17 females, median 43 years (range 30-74)) with acromegaly were treated with FSRT (conformal dynamic arcing, dose 54 Gy, 27-30 fractions) between January 1998 and April 2007. Of the 34 patients, 32 had undergone transsphenoidal adenotomy, and 28 were on medical therapy before FSRT. Patients on medical therapy continued this during and after the irradiation. The treatment was gradually decreased/withdrawn after careful assessment.

RESULTS

Magnetic resonance scanning of the pituitary gland 34 months (median, range 11-95) after irradiation showed stable or reduced volume of the remaining tumour tissue in 31 of 34 patients (91%). Seventeen patients (50%) were biochemically controlled (normalised nadir GH during oral glucose tolerance test and IGF1 <+2 S.D.) 30 months after FSRT (median, range 6-60), and ten of them had true biochemical remission (off medical therapy) 30 months after FSRT (median, range 12-69). Of 28 patients with one or more functioning pituitary axes before irradiation, 8 (29%) developed further deficit of one or two pituitary axes 48 months (median, range 6-102) after FSRT. Of 34 patients, 20 still required medical treatment for acromegaly at the end of this study, mainly those with a short follow-up period after irradiation.

CONCLUSION

The FSRT seems promising in terms of treatment of acromegaly. Longer follow-up is, however, needed to assess the overall efficacy and safety of FSRT for acromegaly.

The role of stereotactic radiotherapy in patients with growth hormone-secreting pituitary adenoma

CONTEXT

Single-session stereotactic radiotherapy (SR) may be a potential adjuvant treatment in acromegaly.

OBJECTIVE

We analyzed the safety and efficacy of SR in patients who had previously received maximal surgical debulking at our center.

DESIGN

The study was a retrospective analysis of hormonal, radiological, and ophthalmologic data collected in a predefined protocol from 1994 through 2006.

SETTING

The study was performed at a university hospital.

PATIENTS

Eighty-three acromegalic patients, 52 women and 31 men, with a mean age of 42.6 +/- 1.2 yr, participated in the study. The median follow-up was 69 months (interquartile range 44-107 months).

INTERVENTION

The patients were treated with SR for residual or recurrent GH-secreting adenoma.

MAIN OUTCOME MEASURE

Normalization of age- and sex-adjusted IGF-I levels together with a basal GH level below 2.5 microg/liter without concomitant GH-suppressive drugs was the goal of therapy.

RESULTS

Fifty patients (60.2%) reached the main outcome of the study. The rate of remission was 52.6% at 5 yr [95% confidence interval (CI) 40.6-64.6%]. Another 13 patients (15.7%), who were resistant to somatostatin analogs, were in remission after SR. Multivariate analysis showed that low basal GH and IGF-I levels were associated with a favorable outcome. No serious side effects occurred after SR. The 5-yr cumulative risk of new onset hypogonadism, hypothyroidism, or hypoadrenalism was 3.6% (95% CI 0-8.6%), 3.3% (95% CI 0-7.7%), and 4.9% (95% CI 0-10.4%), respectively.

CONCLUSION

In a highly selected group of acromegalic patients, SR treatment had good efficacy and safety. This may lead to reconsider the role of SR in the therapeutic algorithm of acromegaly.

Sustained clinical inactivity and stabilization of GH/IGF-1 levels in an acromegalic patient after discontinuation of somatostatin analogue treatment

BACKGROUND

A 38-year-old woman first presented complaining of foot enlargement, finger numbness, arthralgia, fatigue, galactorrhoea and oligomenorrhea. Her symptoms in conjunction with her coarsened facial features and prognathism led to the suspicion of acromegaly.

BASIC PROCEDURES

Oral glucose tolerance tests (OGTT) were performed at initial presentation and almost yearly thereafter for a period of 14 years. Pituitary computerized tomographies (CT) were performed annually for the first six years and magnetic resonance imaging every two years thereafter.

MAIN FINDINGS

The diagnosis of acromegaly was confirmed by OGTT at presentation. A pituitary CT revealed a large invasive pituitary macroadenoma. She remained acromegalic after adenomectomy (evidently partial tumor resection), but was controlled with subsequent long-term somatostatin analogue (SRL) administration. After eight years of SRL administration, she had acceptable stabilization of acromegaly and at that point SRL administration was discontinued. The patient maintained the same control for the following six years up to the present time without further SRL administration.

PRINCIPAL CONCLUSION

This is the first case with stabilization of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) to nearly normal levels and clinical inactivity of acromegaly after withdrawal of long-term treatment with SRLs.

Proton stereotactic radiosurgery in management of persistent acromegaly

OBJECTIVE

To evaluate the efficacy and safety of proton stereotactic radiosurgery (PSRS) for acromegaly that is refractory to surgical treatment and medication.

METHODS

From 1992 to 2003, 22 patients were treated at our institution for persistent acromegaly with use of PSRS. All patients had undergone at least one transsphenoidal surgical procedure without biochemical cure. The median treatment dose delivered during PSRS was 20 (range, 15 to 24) cobalt gray equivalents.

RESULTS

Follow-up was available for all patients at a median of 6.3 (range, 2.5 to 14.2) years after PSRS. A response to PSRS was observed in 21 of 22 patients (95%). A complete response (CR), defined as sustained (> or =3 months) normalization of insulinlike growth factor-I without medical suppression, was attained in 13 patients (59%). Among patients with CR, the median time to CR was 42 (range, 6 to 62) months. No visual complications, seizures, clinical evidence of brain injury, or secondary tumors were noted on regular magnetic resonance imaging scans. One patient had complete pituitary dysfunction before PSRS and was therefore excluded from evaluation for failure. Of the other 21 patients, 8 (38%) had new pituitary deficits.

CONCLUSION

These results demonstrate that PSRS is effective for persistent acromegaly, with 59% of patients attaining normal insulinlike growth factor-I levels without use of any medication after a median of 6.3 years. Our findings indicate that radiosurgery results in an expeditious biochemical response with low morbidity.

Measurement of basal growth hormone (GH) is a useful test of disease activity in treated acromegalic patients

BACKGROUND

Nadir GH during oral glucose tolerance test (OGTT) is the gold-standard test of GH secretion in treated acromegaly. However, it was recently reported that variability in GH is reduced postradiotherapy, making basal GH a potential surrogate marker for nadir GH in such patients.

OBJECTIVE

We aimed to investigate how predictive basal GH is of nadir GH and IGF-I, and whether radiotherapy influenced these relationships.

DESIGN

A total of 226 pairs of basal and nadir GH values from 76 treated acromegalic patients were analysed. Basal GH was defined as the fasting serum GH immediately prior to OGTT.

RESULTS

A highly positive linear correlation (Pearson correlation = 0.955, P < 0.01) between basal and nadir GH was found. Negative predictive value for basal GH < 1 microg/l with respect to nadir GH > 1 microg/l was 100% (53/53 in radiotherapy group, 15/15 in nonradiotherapy group). Positive predictive values for basal GH > 2 microg/l with respect to nadir GH > 1 microg/l for patients treated and not treated with radiotherapy were 96.7% (88/91) and 95.2% (20/21), respectively. No significant difference between concordance of basal and nadir GH with IGF-I in assessment of disease activity was found. Discordance between IGF-I and nadir or basal GH < 1 microg/l was lower in the radiotherapy group than nonradiotherapy group, but this was nonsignificant.

CONCLUSIONS

Basal GH < 1 microg/l and > 2 microg/l are highly predictive of nadir GH < 1 microg/l and > 1 microg/l, respectively, regardless of previous radiotherapy. Basal GH is as good as nadir GH in concordance with IGF-I. We therefore suggest basal GH is a useful test of disease activity in treated acromegaly, and can reliably replace OGTT unless basal GH is between 1 microg/l and 2 microg/l.

Resolution of diabetes mellitus but not acromegaly in a cat with a pituitary macroadenoma treated with hypofractionated radiation

The use of insulin-like growth factor 1 assays in the diagnosis and subsequent monitoring after radiotherapy of an acromegalic cat with a secretory pituitary adenoma and secondary insulin-resistant diabetes mellitus is described. Diabetes resolved, and exogenous insulin was no longer required for the maintenance of normoglycaemia 10 months after completion of a course of hypofractionated radiotherapy. However, insulin-like growth factor 1 remained elevated, and the cat's size and appetite continued to increase. It is suggested that radiotherapy may decrease growth hormone concentration to a level such that diabetogenic effects are no longer evident but not to a level required to decrease insulin-like growth factor 1 secretion.

Gamma knife radiosurgery for acromegaly--long-term experience

OBJECTIVE

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Role of radiotherapy in the management of acromegaly

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

Feline Acromegaly: A Review of the Syndrome

Acromegaly is characterized by chronic excessive growth hormone (GH) secretion by the pituitary gland. Feline acromegaly is most commonly caused by a functional pituitary tumor. Definitive diagnosis can be difficult because of the gradual disease onset, subtle clinical signs, unavailability of relevant laboratory tests, and client financial investment. The most significant clinical finding of acromegaly is the presence of insulin-resistant diabetes mellitus. Diagnosis is currently based upon brain imaging and measurement of serum GH and/or insulin-like growth factor-1 concentrations. Definitive treatment in cats is not well described, but radiation therapy appears promising.

Long-term results of gamma knife surgery for growth hormone-producing pituitary adenoma: is the disease difficult to cure?

OBJECT

The authors conducted a study to determine the long-term results of gamma knife surgery for residual or recurrent growth hormine (GH)-producing pituitary adenomas and to compare the results with those after treatment of other pituitary adenomas.

METHODS

The series consisted of 67 patients. The mean tumor diameter was 19.2 mm and volume was 5.4 cm3. The mean maximum dose was 35.3 Gy and the mean margin dose was 18.9 Gy. The mean follow-up duration was 63.3 months (range 13-142 months). The tumor resolution rate was 2%, the response rate 68.3%, and the control rate 100%. Growth hormone normalization (GH < 1.0 ng/ml) was found in 4.8%, nearly normal (< 2.0 ng/ml) in 11.9%, significantly decreased (< 5.0 ng/ml) in 23.8%, decreased in 21.4%, unchanged in 21.4%, and increased in 16.7%. Serum insulin-like growth factor (IGF)-1 was significantly decreased (IGF-1 < 400 ng/ml) in 40.7%, decreased in 29.6%, unchanged in 18.5%, and increased in 11.1%, which was almost parallel to the GH changes.

CONCLUSIONS

Gamma knife surgery was effective and safe for the control of tumors; however, normalization of GH and IGF-1 secretion was difficult to achieve in cases with large tumors and low-dose radiation. Gamma knife radiosurgery is thus indicated for small tumors after surgery or medication therapy when a relatively high-dose radiation is required.

Treatment of Acromegaly

Mortality is increased in individuals with acromegaly unless serum growth hormone (GH) levels are below 2 microg/l and serum insulin-like growth factor (IGF)-I levels are normal following treatment. These combined criteria have been used to define remission of the disorder in this review. Transsphenoidal surgery achieves remission targets in an average of 55% of patients. For those not in remission following surgery, options include repeat surgery or use of adjuvant therapy. Fractionated external beam pituitary radiotherapy achieves 10-year remission rates of 47% but leaves patients exposed to excess GH until remission occurs. Stereotactic radiotherapy and gamma knife radiosurgery achieve remission rates of 40% over 3 years, and dopamine agonists produce remission in about 20% of patients. Somatostatin analogues induce remission in 59% of patients within the first year of treatment. The GH receptor antagonist pegvisomant leads to remission in 90% of patients, using IGF-I levels for assessment. Optimal treatment for a patient with acromegaly thus depends on the likely efficacy of treatment, cost, surgical skill, severity of side effects, tolerability, control of tumour growth, and improvement in complications related to tumour mass. A primary surgical approach, followed by medical therapy for those not in remission, remains the preferred option in most centres.

Quantification of in vivo Photofrin uptake by human pituitary adenoma tissue

OBJECT

Photofrin is widely distributed in the body after intravenous injection. This study was designed to quantify the preferential uptake of Photofrin by pituitary adenoma tissue for intraoperative photodynamic therapy.

METHODS

Eight patients (seven men) with recurrent pituitary adenomas who had undergone previous surgery and radiation therapy were recruited for a Phase I/II feasibility study of the application of photodynamic therapy to pituitary tumors. Photofrin was administered intravenously at a dose of 2 mg/kg body weight 48 hours before repeated transsphenoidal hypophysectomy was performed. At the time of the operation, pituitary adenoma tissue, muscle, fat, skin, and plasma were obtained for measurement of Photofrin content by fluorometric assay. The mean Photofrin level in pituitary adenoma tissue was 6.87 ng/mg (95% confidence interval [CI] 3.99-9.75), which was significantly higher than the uptake by skeletal muscle (2.24 ng/mg, 95% CI 1.28-3.2; p = 0.008), or fat (2.54 ng/mg, 95% CI 0.66-4.42; p = 0.007). Nevertheless, the mean drug concentration in pituitary adenoma tissue was not significantly different from the level in plasma (7.65 microg/ml, 95% CI 5.38-9.90; p = 0.558). Skin specimens were available in four patients, and these showed a mean uptake of 2.19 ng/mg.

CONCLUSIONS

Photofrin is preferentially retained by pituitary adenoma tissue to levels both adequate for intraoperative photodynamic therapy and approximately 50% higher than those reported for gliomas.

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.

Current status and future opportunities for controlling acromegaly

Growth-hormone (GH) secreting adenomas, including acromegaly, account for approximately one-sixth of all pituitary adenomas and are associated with mortality rates at least twice that of the general population. The ultimate goal of therapy for acromegaly is normalization of morbidity and mortality rates achieved through removal or reduction of the tumor mass and normalization of insulin-like growth factor I (IGF-I) levels. Previously published efficacy results of current treatment modalities (surgery, conventional radiation, and medical therapy with dopamine agonists and somatostatin analogs) are often difficult to compare because of the different criteria used to define cure (some of which are now considered inadequate). For each of these modalities, pooled data from a series of acromegaly studies were reviewed for rates of IGF-I normalization, a currently accepted definition of cure. The results showed overall cure rates of approximately 10% for bromocriptine, 34% for cabergoline, 36% for conventional radiation, 50-90% for surgery for microadenomas and less than 50% for macroadenomas, and 54-66% for octreotide. These cure rates based on IGF-I normalization are generally less than those reported for cure based solely on GH levels. Novel new therapies for acromegaly include the somatostatin analog, lanreotide, Gamma Knife radiosurgery, and pegvisomant, the first in its class of new GH receptor antagonists. Although it does not appear that Gamma Knife radiosurgery results in significantly higher cure rates or fewer complications, it does provide a notable improvement in delivery compared with conventional radiation. Early studies have reported IGF-I normalization in 48% of lanreotide-treated patients and up to 97% of pegvisomant-treated.