| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
BRIEF REPORT |
Section of Endocrinology (A.F., A.B., V.C., L.T., F.V., A.P., L.D.M.) and Laboratory of Vascular Biology and Genetics (F.A.), Department of Internal Medicine, Institute of Pathology (L.L., V.V.) and Institute of Neurosurgery (F.D., G.M.), Università Cattolica del Sacro Cuore, 00168 Rome, Italy; Section of Endocrinology (M.C.Z., M.R.A., E.C.d.U.), Department of Biochemical Sciences and Advanced Therapies, University of Ferrara, 44100 Ferrara, Italy; and Department of Internal Medicine (A.G.), University of Brescia, 25125 Brescia, Italy
Address all correspondence and requests for reprints to: Laura De Marinis, M.D., Section of Endocrinology, Department of Internal Medicine, Università Cattolica del Sacro Cuore, Via Cassia 901, 00168 Rome Italy. E-mail: laurademarinis{at}yahoo.it.
 |
Abstract |
|---|
 Top Abstract IntroductionPatients and MethodsResultsDiscussionReferences |
|---|
Objective: The aim of the study was to evaluate the Ki-67 index prognostic relevance in a group of acromegalic patients who underwent transsphenoidal surgery for a GH-secreting pituitary adenoma.
Material and Methods: We selected 68 consecutive acromegalic patients referred to our hospital during a 5-yr period. The Ki-67 index was determined by immunohistochemistry on tissue samples obtained from each adenoma after surgery. Those patients who were not completely cured after surgery began medical therapy with somatostatin analogs (SSAs). Periodical pituitary magnetic resonance imaging and hormonal evaluation were performed during the follow-up.
Results: Twenty-eight of 68 patients were cured after surgery (41%). Among the 40 patients treated with SSAs, 13 were considered uncontrolled. Pituitary magnetic resonance imaging showed residual/recurrent disease in 25 of 68 patients after 6 months. No correlation was found between Ki-67 index and age, tumor size, GH, or IGF-I plasma levels. Tumors described as having cavernous sinus invasion had a higher mean Ki-67 index as compared with noninvasive tumors (P < 0.01). The Ki-67 index was significantly lower in tumors in patients cured after surgery as compared with patients considered not cured (P < 0.01) and in tumors in patients controlled by SSA therapy as compared with patients considered as uncontrolled (P < 0.05).
Conclusion: The Ki-67 labeling index may predict clinical outcome in postsurgical management of acromegalic patients. We suggest routine Ki-67 evaluation in GH-secreting pituitary adenomas.
|
Introduction |
|---|
|
TopAbstractIntroductionPatients and MethodsResultsDiscussionReferences |
|---|
The nuclear antigen Ki-67 is related to growth potential in many human tumors. Some authors report a positive correlation between pituitary tumor Ki-67 expression and pituitary adenoma invasiveness and recurrence (8, 9, 10, 11). However, the significance of the Ki-67 index as a prognostic factor in acromegalic patients remains undefined.
In this study, we aimed to investigate the possible prognostic value of the Ki-67 labeling index in predicting the clinical outcome of acromegalic patients after surgery as well as their response to medical therapy.
|
Patients and Methods |
|---|
|
TopAbstractIntroductionPatients and MethodsResultsDiscussionReferences |
|---|
The study protocol was approved by the Ethical Committee of the Catholic University School of Medicine, and all patients signed an informed consent form. The study population consisted of 68 newly diagnosed acromegalic patients (mean age at diagnosis 42 ± 11 yr, range 21–68 yr), 24 men and 44 women, diagnosed from 2000 to 2005 at the Institute of Endocrinology and operated on at the Department of Neurosurgery of the Catholic University of Rome. Biochemical diagnosis of acromegaly was based on current criteria (12). Exclusion criteria consisted in a history of medical treatment with somatostatin analogs (SSAs), dopamine agonists or GH antagonist before surgery, and previous surgery or radiotherapy for pituitary adenoma.
Pituitary magnetic resonance imaging (MRI) showed the presence of a macroadenoma (maximal diameter > 10 mm) in 53 patients and a microadenoma (maximal diameter < 10 mm) in 15 patients. Pituitary tumors were classified into three groups according to tumor size: group 1 with maximum diameter 10 mm or less; group 2 with maximum diameter greater than 10 mm but 20 mm or less; group 3 with maximum diameter greater than 20 mm. Pituitary tumors were described as having an extrasellar extension in 15 cases, being parasellar in six, para- and suprasellar in four, and suprasellar in five cases. Invasion of the cavernous sinus was described at MRI in 16 cases.
A transsphenoidal approach was pursued in 67 patients, whereas a pterional approach was used in a patient with a macroadenoma displaying suprasellar extension.
Postsurgical evaluation
Biochemical reevaluation was performed after 6–12 wk by oral glucose tolerance test (OGTT) and serum IGF-I levels evaluation in all subjects. Pituitary MRI was performed after 6 months and then once a year. Patients were considered cured according to the Cortina criteria (13). Patients who were considered as not surgically cured started medical therapy with long-acting SSA octreotide 20 mg every 4 wk, and the dose was increased up to 30 mg every 3 wk in uncontrolled patients.
Patients were considered as uncontrolled on the basis of the clinical picture, nadir GH after OGTT higher than 1 ng/ml, and plasma IGF-I levels higher than age- and sex-matched normal subjects. Patients with a persistent disease were reevaluated every 6 months by means of serum IGF-I levels and OGTT. Postsurgical follow-up ranged from 12 to 48 months.
Hormonal assessment
Plasma GH levels were measured by an immunoradiometric assay kit (Radim, Pomezia, Italy). The inter- and intraassay coefficients of variation were 5.8–8.5 and 2.5–3.9%, respectively. Plasma IGF-I levels were measured by an immunoradiometric assay kit (Medgenix Diagnostix SA, Fleurus, Belgium). The inter- and intraassay coefficients of variation were 9.6 and 4.1%, respectively.
Immunohistochemistry
All tissue specimens were examined for anterior pituitary hormones [GH, prolactin (PRL), FSH, LH, TSH, ACTH] via immunohistochemistry, following standard procedures.
Formalin-fixed, paraffin-embedded sections 5 µm thick of all pituitary tumors and 10 normal anterior pituitary glands were deparaffinized, rehydrated, and heated in a microwave oven in pH 6 citric acid buffer at 100 C for 15 min. The immunoreaction was revealed by using a Perox-DAB kit (HSL60-DAB; Sky-Tek, Logan, UT). The tumor sections were incubated with a primary antibody for 18 h in a humid chamber at 4 C. Diaminobenzidine was used as a chromogen, followed by a weak nuclear counterstain.
The monoclonal antibody MIB-1 directed against the Ki-67 antigen was purchased from Dako (Glostrup, Denmark) and diluted according to the manufacturer’s instructions. Preimmune mouse IgG (Sigma-Aldrich Corp., St. Louis, MO) was used as a negative control. Ki-67/MIB-1 was evaluated, in each case, in at least five representative tissue areas, with at least 1000 cells each. Immunohistochemical protein expression was scored blindly by one operator (L.L.) at the Catholic University of Rome. Images were digitally acquired with a Nikon Coolpix 5000 digital camera (Tokyo, Japan) mounted on a Zeiss Axioskop 2 microscope (Jena, Germany). Both immunolabeled and unlabeled nuclei were evaluated and the percentage of positive cells was calculated.
Statistical analysis
Data are expressed as mean ± SD. Statistical analysis was performed using Minitab software for Windows (Minitab Inc., State College, PA). Results were analyzed for statistically significant differences using the Mann-Whitney test or the 
2 test where appropriate. P < 0.05 was considered significant.
|
Results |
|---|
|
TopAbstractIntroductionPatients and MethodsResultsDiscussionReferences |
|---|
Mean presurgical GH nadir after OGTT was 20 ± 22 ng/ml and significantly decreased after surgery (3 ± 5 ng/ml; P < 0.01). Mean presurgical IGF-I levels were 721 ± 266 ng/ml, and significantly decreased after surgery (309 ± 191 ng/ml; P < 0.01). Surgery was considered as successful in 28 of 68 patients (41%) (group A) (Table 1
). Among the 40 patients treated with SSAs, 27 were considered as controlled (group B) and 13 as uncontrolled (group C) (Table 1). Residual/recurrent disease was detected at pituitary MRI after 6 months in 25 of 68 patients (37%).
|
Immunohistochemistry showed PRL immunostaining in 25 patients, among which 17 presented with high serum PRL levels before surgery. TSH, FSH, and LH immunoreactivity was detected in seven, three, and two tumors, respectively, not corresponding to an increased hormone serum level before surgery.
Ki-67 immunostaining was detected in all 68 samples, with a mean value of 1.5 ± 1.3%. On the contrary, normal pituitaries completely lacked in Ki-67 immunoreactivity.
Relationship between Ki-67 and clinical characteristics
No correlation was found between Ki-67 index and age, pre- or postsurgical GH nadir after OGTT, or IGF-I plasma levels. However, tumors from patients cured after surgery showed a significantly (P < 0.01) lower mean Ki-67 value (1.1 ± 0.8%) (group A), compared with patients considered as not cured (1.8 ± 1.5%) (Fig. 1). Tumors from patients controlled by SSA therapy showed a significantly (P < 0.05) lower mean Ki-67 value (1.5 ± 1.2%) (group B), compared with patients considered as uncontrolled (2.4 ± 1.9%) (group C) (Table 1
). On the other hand, mean Ki-67 index was not significantly different according to tumor size (1.2 ± 1.1% for group 1; 1.2 ± 0.6% for group 2; 2.2 ± 2.1% for group 3) and extension (1.8 ± 1.8% for extrasellar tumors and 1.5 ± 1.1% for intrasellar tumors, respectively). However, tumors described as having cavernous sinus invasion had a higher mean Ki-67 index (2.5 ± 2.1%), compared with noninvasive tumors (1.1 ± 0.7%) (P < 0.01).
|
|
Discussion |
|---|
|
TopAbstractIntroductionPatients and MethodsResultsDiscussionReferences |
|---|
In keeping with previous evidence, we found that the Ki-67 index was not significantly different according to tumor size or extension (14, 15). Losa et al. (16) found opposing results. This discrepancy might be due to a different balance between adenoma growth fraction and loss of tumor cells by apoptosis in determining pituitary tumor size. Moreover, tumor size can be influenced by the growth rate of the adenoma.
Previous studies evaluated the relationship between Ki-67 index and invasive potential of GH-secreting pituitary adenomas.
Iuchi et al. (15) observed that tumors with a high grade of invasiveness of cavernous sinus had elevated levels of the Ki-67 antigen. This result was confirmed in the study by Losa et al. (16). Our data on a larger series of acromegalic patients are in agreement with both studies. However, other authors failed to find such a correlation in a series of 11 GH-secreting pituitary adenomas (17). This discrepancy might be due to the different sample size and the higher percentage of macroadenomas in our series.
We provide the first evidence that a lower Ki-67 labeling index is associated with a better clinical outcome in a large series of patients with GH-secreting pituitary adenomas. The better clinical outcome of acromegalic patients with adenomas with a lower Ki-67 index might be explained by the lower invasive potential as well as by the lower growth fraction of the adenoma.
Both age and hormonal levels are well-known predictive factors for postsurgical cure in acromegaly. In our homogeneous series of acromegalic patients, we did not find a correlation between age or hormonal levels and the Ki-67 index, in accordance with other studies (15, 16, 17). The Ki-67 index gives further information about the infiltrative behavior of a GH-secreting pituitary adenoma, which depends only to a small extent on the patients’ age or hormonal secretion. Therefore, Ki-67 may represent an adjunctive predictive factor of cure in acromegaly.
In acromegalic patients, the variable response to SSAs is mainly related to somatostatin receptor subtypes expressed by the adenoma (18). Moreover patients’ age, tumor size, presurgical hormonal levels, and morphological characteristics of the adenoma might predict response to SSA therapy (19, 20). We provide the first evidence that response to SSA therapy in GH-secreting pituitary tumors not cured by surgery is more likely in cases with a lower Ki-67 index. This finding may depend on different somatostatin receptor subtypes distributions in the tumors with different proliferation index and should be further investigated.
In conclusion, this study suggests that: 1) in acromegalic patients, the Ki-67 labeling index represents a useful prognostic marker of cure after adenomectomy; 2) the Ki-67 index can identify acromegalic patients who are more likely to respond to medical therapy with SSAs; and 3) the Ki-67 index can provide further information about patients’ follow-up and initiation of medical therapy.
|
Footnotes |
|---|
First Published Online May 6, 2008
Abbreviations: MRI, Magnetic resonance imaging; OGTT, oral glucose tolerance test; PRL, prolactin; SSA, somatostatin analog.
Received January 18, 2008.
Accepted April 25, 2008.
|
References |
|---|
|
TopAbstractIntroductionPatients and MethodsResultsDiscussionReferences |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
