The role of somatostatin receptor scintigraphy in patients with

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					The British Journal of Radiology, 78 (2005), 110–115          E   2005 The British Institute of Radiology
DOI: 10.1259/bjr/51245688

The role of somatostatin receptor scintigraphy in patients
with pituitary adenoma or post-surgical recurrent tumours
1              ´
    Department of Nuclear Medicine, Virgen de las Nieves Hospital, Avda. de las Fuerzas Armadas 2, 18014 Granada and
                                                               ´      ´
    Department of Neurosurgery, University Hospital ‘‘Reina Sofıa’’, Cordoba, Spain

        Abstract. To assess the role of scintigraphy with 111In-DTPA-D-Phe-octreotide (111In-octreotide) in the
        diagnosis of pituitary adenomas and in the evaluation of post-surgical recurrent or residual tumours, we
        performed scintigraphy with 111In-DTPA-D-Phe-octreotide (SRS) in 35 patients: 14 patients with confirmed
        pituitary tumours and 15 with confirmed recurrent tumours. Clinical, biochemical and histological analyses,
        conventional images (CT/MRI), and follow-up assessments during a period of 1 year to 4 years were recorded in
        all patients. In the present study, scintigraphy with 111In-octreotide showed positive uptake in 10 out of 14
        patients with confirmed pituitary tumour and in 13 out of 15 patients with confirmed recurrent tumour, with an
        overall sensitivity of 79%. SRS showed better results in growth hormone (GH)- and prolactin (PRL)-secreting
        tumours (7/8 patients correctly identified) than in other adenomas (3/9). SRS detected recurrence of
        adenocorticotrophic hormone (ACTH)-secreting tumours (4/5 patients correctly identified) and non-secreting
        tumours (5/7 patients correctly identified). 111In-octreotide scintigraphy, in combination with other imaging
        modalities, is useful in the diagnosis and follow-up of pituitary tumours. It allows scar tissue to be differentiated
        from tumour recurrence after surgical treatment and ensures better selection of patients who will benefit from
        medical treatment with somatostatin analogues.

   The in vivo visualization of somatostatin receptors is                 chiasm. MRI signal characteristics do not necessarily
becoming more widely used to diagnose neuroendocrine                      assess the consistency of the tumour accurately but the
tumours and to assess the therapeutic effects of somato-                  superior and inferior extent of tumour is well demon-
statin analogues in these patients [1]. Somatostatin                      strated by MRI.
receptors have been demonstrated in vitro in most cases                      It is not easy to distinguish between recurrent/residual
of growth hormone (GH)-secreting adenomas and in some                     tumour and scar/necrotic tissue after surgery [7]. The
cases of thyroid stimulating hormone (TSH)-secreting                      scintigraphic visualization of hypophyseal tumours may be
adenomas and prolactinomas. Controversial results have                    of value for predicting the response to somatostatin
been reported in other types of pituitary adenomas, such                  analogue treatment and for the post-surgical detection of
as non-secreting adenomas [2–5]. GH-secreting tumours                     small or residual tumours that are undetectable on MRI.
express somatostatin receptor subtypes 2, 3 and 5, whereas                Although some authors have reported that somatostatin
non-secreting adenomas mainly express subtype 3 [6].                      receptor scintigraphy (SRS) did not permit visualization of
   In the diagnostic work-up of patients with pituitary                   post-surgical tumours that were not visible on MRI [8],
adenomas, CT and MRI play a principal role in defining                     other authors have described its utility to detect minimal
the localization and tumour size, as in all brain tumours,                post-surgical residual tumours [9].
but histological diagnosis can only be performed post-                       The present study aimed to assess the utility of SRS in
operatively. MRI is now the investigation of choice in                    the diagnosis of pituitary adenomas and in the evaluation
diagnosis of pituitary adenomas. Micro-adenomas are                       of post-surgical recurrent or residual tumours.
defined as being smaller than 10 mm in size and usually
present because of endocrine dysfunction (the most
common is prolactinoma). 80–85% of micro-adenomas                         Patients and methods
are visible on unenhanced T1 weighted MR images and
33–50% are seen as areas of hyperintensity on T2 weighted                 Patients
images, and enhancement with dynamic scanning is only
                                                                             We performed a prospective study of 35 patients
necessary in a minority of cases. Macro-adenomas are
                                                                          referred to our Department of Nuclear Medicine for
more likely to be non-functioning and present because of
                                                                          suspicion of pituitary tumour or suspicion of pituitary
mass effect on adjacent structures such as the optic
                                                                          tumour recurrence over 5 years (1997–2001). 35 patients
Received 6 April 2004 and in revised form 23 August 2004, accepted 27     (23 females, 12 males) aged between 9 years and 77 years
September 2004.                                                           (mean age 43 years) were referred by the Departments of
Address correspondence to Dr Maria Angustias Muros, Servicio de
                                                                          Neurosurgery, Endocrinology and Radiotherapy. All
Medicina Nuclear, Hospital Virgen de las Nieves, Avda. Fuerzas            patients gave their informed consent to undergo the
Armadas, 2, 18014 Granada, Spain.                                         scintigraphy. The Ministry of Health approved the

110                                                                                    The British Journal of Radiology, February 2005
Somatostatin receptor scintigraphy in pituitary adenomas

compassionate use of the radiopharmaceutical in all cases.     N    Grade II: moderate tracer uptake with good visualiza-
18 of the patients were referred for suspected tumour               tion of tumour; uptake slightly greater than that in
recurrence due to the persistence or post-surgical onset of         skull;
clinical symptoms (n59) or elevated levels of hormone          N    Grade III: intense tracer uptake; uptake clearly greater
markers (n59). Tumour types in these patients included:             than that in skull.
adenocorticotrophic hormone (ACTH)-secreting (n55),
GH-secreting (n53), prolactin (PRL)-secreting (n52),
follicle stimulating hormone (FSH)-secreting adenomas          MRI
(n51) and non-secreting adenomas (n57). The remaining
17 patients were referred for suspicion of pituitary              MRI was performed using a 0.5-T scanner (GE Max
adenomas, presenting with PRL-secreting (n54), GH-             Medical System, Milwaukee, WI). T1 weighted gradient
secreting (n54), ACTH-secreting (n53) adenomas, non-           echo imaging (without contrast) was performed with a
secreting adenomas (n53), and thyroid stimulating              repetition time (TR) of 380 ms and echo time (TE) of
hormone (TSH)- (n51), FSH- (n51), and leutinizing              12 ms. T2 weighted and proton density variable echo (VE)
hormone (LH)- (n51) secreting adenomas. None of 18             imaging was performed with a TR of 2600 ms, TE of 40–
patients referred for suspected tumour recurrence were         120 ms, and T1 weighted spin-echo (SE) with a TR of
included in the primary tumours group.                         600 ms, and TE of 25 ms. Studies were also performed
   Clinical data and biochemical determinations were           with paramagnetic contrast: T1 weighted SE imaging,
recorded for all patients prior to the scintigraphic           using sections of 3 mm thickness with 4 mm section
examination. The analytical findings included levels of         interval. Images were obtained in the coronal and axial
GH, somatomedin C, insulin-like growth factor-1 (IGF1)         planes.
growth factor, prolactin, TSH, ACTH, FSH, and LH, and
the results of stimulation and inhibition tests of these
hormones. CT or MRI and ophthalmological (visual field)         CT
studies were carried out in all cases. The mean follow-up         CT scan was carried out before and after intravenous
period was 2.5 years (range 1–4 years).                        infusion of contrast medium using a third generation
   A tailored therapeutic approach was developed for           Siemens Somatom CR scanner. Section thickness was 4 mm.
each patient, using somatostatin analogues, radio-
surgery, medical treatment or surgery as appropriate.
Five patients (three with pituitary adenomas and two with      Analytical studies: hormone determinations
tumour recurrence) underwent surgery and the path-
ological report confirmed the presence of pituitary                The following hypophyseal hormones were determined
adenoma or tumour recurrence. The diagnosis was                in all patients: GH, ACTH, PRL, TSH, FSH, and LH.
confirmed in the remainder by imaging tests (CT or              IGF1 growth factor was also measured. The determina-
MRI) in conjunction with analytical results and clinical       tions were made by radioimmunoanalytical techniques for
findings.                                                       FSH, LH and PRL (Diagnostic System Laboratories, Inc.,
                                                               TX), GH (IRMA, Immunotech, France), TSH (IRMA,
                                                               Immunodiagnostic Systems Ltd., UK), and ACTH
                                                               (Nichols Institute, CA, USA). Hormone inhibition and
[111In-DTPA-D-Phe]-octreotide scintigraphy                     stimulation tests were carried out: inhibition test with
   The scintigraphy was performed with 185–220 MBq             dexamethasone for ACTH-secreting tumours and oral
(5–6 mCi) of 111In-chloride-DTPA-D-Phe-octreotide              glucose overload test for GH-secreting tumours.
(Octreoscan) obtained from a simple Mallinckrodt kit
(Mallinckrodt Iberica S.A. Spain), which was intrave-
nously administered to all patients. No post-administra-       Follow-up
tion adverse reactions or side effects were detected in any       All patients were followed up every 6 months, provided
patient. Image acquisition was with single-head (Siemens       no clinical situations occurred requiring more urgent
Orbiter; Gammasonics, IL) and double-head (AXIS2;              assessment or admission. The follow-up consisted of:
Picker International, Nuclear Medicine Division,               MRI examinations, which were always compared with
Cleveland, OH) gamma cameras with medium energy                previous images, hormonal analytical determinations, and
collimator. Planar images were obtained 4 h, 24 h and          clinical examinations.
48 h post-injection in all patients, with at least 500 000        Complete remission was defined as normalization of all
counts/acquired per image or 10 min image21.                   clinical sings with normal tumour markers (including basal
Tomographic images (SPECT) were obtained 4 h and               and dynamic responses of hypophyseal hormones) at 1
24 h post-injection, if using the double-head camera,          year after therapy with no evidence of residual tumour on
through a 360 ˚ orbit, acquiring 60 steps at 40 s step21,      CT or MRI. The patient was considered to have tumour
using a 64664 matrix. The image analysis was performed         recurrence if clinical, biochemical and/or neuroradiological
by two nuclear medicine specialists according to a             signs of tumour activity were detected after therapy.
qualitative evaluation system visually comparing the
tracer uptake in the suspected tumour with that in the
skull [10–12]. The grades were defined as follows:              Results
N   Grade 0: absence of tracer uptake, no visualization of       Among the 17 patients referred for suspicion of pituitary
    tumour activity, considered negative;                      tumour, SRS was positive in 10 patients (Table 1,
N   Grade I: slight tracer uptake, similar to that in skull;   Figure 1). The MRI was positive in all 10 patients. Two

The British Journal of Radiology, February 2005                                                                         111
                                                                            M J Acosta-Gomez, M A Muros, J M Llamas-Elvira et al

Table 1. Data of patients with suspected pituitary adenoma

N˚    Sex/age   Tumour type      SRS            MRI             Size (cm)    Treatment                  Follow up
 1    F/55      PRL-secreting    Positive-III   Positive        3.3          Somatostatin analogues     Size reduction, clinical
                                                                                                          improvement (TP)
 2    M/52      PRL-secreting    Positive-III   Positive        6            Somatostatin analogues     Complete remission (TP)
 3    F/14      PRL-secreting    Positive-II    Positive        2.5          Radiosurgery               Size reduction (TP)
 4    M/64      PRL-secreting    Negative       Positive        1.6          Radiosurgery               Size reduction (FN)
 5    F/67      GH-secreting     Positive-I     Positive        0.8          Somatostatin analogues     Size reduction (TP)
 6    F/42      GH-secreting     Positive-II    Positive        1.2          Somatostatin analogues     Size reduction, clinical
                                                                                                          improvement (TP)
 7    M/40      GH-secreting     Positive-I     Positive        0.3          Radiosurgery               Complete remission (TP)
 8    F/44      GH-secreting     Positive-III   Positive        2.5          Surgery                    Complete remission (TP)
 9    M/57      Non-secreting    Positive-II    Positive        2.5          Surgery                    Complete remission (TP)
10    F/67      Non-secreting    Negative       Positive        2.7          Medical                    Clinical improvement (FN)
11    F/66      Non-secreting    Negative       Positive        2            None                       Stable (FN)
12    F/65      ACTH-secreting   Negative       Positive        0.9          Surgery                    Complete remission (FN)
13    F/76      ACTH-secreting   Negative       Negative        no mass      None                       Without symptom, MRI (-) (TN)
14    F/42      ACTH-secreting   Negative       Negative        no mass      None                       Without symptom, MRI (-) (TN)
15    F/14      FSH-secreting    Negative       Positive (FP)   1            None                       Without symptom, MRI (-) (TN)
16    F/9       LH-secreting     Positive-II    Positive        0.2          Medical                    Clinical improvement (TP)
17    M/68      TSH-secreting    Positive-III   Positive        2.5          Somatostatin analogues     Clinical improvement (TP)

SRS, somatostatin receptor scintigraphy; PRL, prolactin; GH, growth hormone; ACTH, adenocorticotrophic hormone; FSH, follicle
  stimulating hormone; LH, leutinizing hormone; TSH, thyroid stimulating hormone; TP, true positive; TN, true negative; FN, false
  negative; FN, false positive.

of these 10 patients underwent surgery and the patholo-                II or III and two patients with Grade I. Each patient with
gical report confirmed the presence of pituitary adenoma;               Grade I had GH-secreting adenoma less than 1 cm in size.
six patients were treated with somatostatin analogues, and                SRS was negative in seven patients. In three of these, the
the remaining two patients (with smaller tumour size)                  absence of the disease was confirmed by conventional
received radiosurgery or medical treatment. In follow-up               imaging studies, biochemical findings, and clinical follow-
studies, all 10 patients showed clinical, biochemical and/or           up. The initial MRI examination was positive in one case
radiographic improvements after therapy. According to                  (N˚ 15), but subsequent biochemical and clinical follow-up
their tracer uptake, eight patients were scored with Grades            ruled out the presence of adenoma in this patient.

                                 (a)                                                              (b)

Figure 1. (a) Anterior and (b) lateral images of 111In-chloride-DTPA-D-Phe-octreotide accumulation in the tumour site in a patient
(N˚ 17) with thyroid stimulating hormone (TSH)-secreting adenoma. The images were taken in a Siemens single-head gamma camera
24 h after tracer administration.

112                                                                                  The British Journal of Radiology, February 2005
Somatostatin receptor scintigraphy in pituitary adenomas

Table 2. Data of patients with suspected recurrent pituitary adenoma

N˚ Sex/age Tumour type        SRS            MRI        Size (cm)      Treatment                 Follow up
18 M/32      ACTH-secreting Positive-III Positive       small nodule  Somatostatin               Complete remission (TP)
19 F/51      ACTH-secreting Positive-II      Negative   2.5           Radiosurgery and           Complete remission (TP)
20   F/66    ACTH-secreting   Positive-I     Positive   2.5           Radiosurgery               Size reduction (TP)
21   F/37    ACTH-secreting   Positive-II    Positive   small nodule Medical                     Size reduction (TP)
22   F/34    ACTH-secreting   Negative       Positive   small nodule Medical                     Without symptom, MRI (-) (TN)
23   M/56    Non-secreting    Positive-II    Positive   scant remains Somatostatin analogues     Clinical improvement (TP)
24   M/54    Non-secreting    Positive-II    Positive   3.8           Somatostatin analogues     Clinical improvement (TP)
25   M/36    Non-secreting    Positive-I     Negative   no mass       Medical                    Clinical improvement, MRI (+) (TP)
26   M/66    Non-secreting    Negative       Negative   no mass       None                       Without symptom, MRI (-) (TN)
27   M/56    Non-secreting    Positive-I     Positive   2.9           None                       Stable (TP)
28   F/40    Non-secreting    Positive-I     Positive   2             Somatostatin               Clinical improvement (TP)
29   F/46    Non-secreting    Negative       Positive   1.6           Radiosurgery               Clinical improvement (FN)
30   F/50    GH-secreting     Positive-II    Positive   2             Somatostatin analogue      Complete remission (TP)
31   F/45    GH-secreting     Negative       Negative   no mass       None                       Without symptom, MRI (-) (TN)
32   F/33    GH-secreting     Negative       Positive   1             Radiotherapy               Clinical improvement (FN)
33   F/77    PRL-secreting    Positive-II    Positive   5             Surgery                    Clinical improvement (TP)
34   M/47    PRL-secreting    Positive-I     Positive   2             Medical                    Complete remission (TP)
35   F/32    FSH-secreting    Positive-III   Positive   4.6           Somatostatin analogues     Size reduction (TP)

ACTH, adenocorticotrophic hormone; GH, growth hormone; PRL, prolactin; FSH, follicle stimulating hormone; SRS, somatostatin
 receptor scintigraphy; TP, true positive; TN, true negative; FN, false negative; FN, false positive.

  Scintigraphy failed to detect the presence of tumour in                 Among the 18 patients examined for recurrent/residual
four patients: two with non-secreting adenomas, one with               pituitary tumour, SRS was positive in 13 patients
an ACTH-secreting adenoma of less than 1 cm, and one                   (Table 2). Of these, one (with largest tumour size)
with a prolactinoma.                                                   underwent repeat surgery, five (with highest uptake
  SRS showed better results in GH- and PRL-secreting                   grades, II and III) were treated with somatostatin
tumours (7/8 patients correctly identified) than in other               analogues, two with radiosurgery, three underwent
adenomas (3/9).                                                        medical treatment and one patient was treated with

                                (a)                                                              (b)

Figure 2. (a) MRI in the patient N˚ 21. Represent a study in a coronal view showing a small recurrent tumour in contact with right
optic nerve. (b) Lateral images of 111In-chloride-DTPA-D-Phe-octreotide accumulation in the recurrent tumour site in a patient (N˚
21) with recurrent adenocorticotrophic hormone (ACTH)-secreting adenoma. The images were taken in a Siemens single-head gamma
camera 24 h after tracer administration.

The British Journal of Radiology, February 2005                                                                                113
                                                                   M J Acosta-Gomez, M A Muros, J M Llamas-Elvira et al

radiotherapy and somatostatin analogues. The remaining           suspicion of FSH- and LH-secreting tumours were
patient (N˚ 27) refused treatment. In all 13 patients, the       correctly diagnosed using SRS. The utility of SRS was
recurrence was confirmed by clinical and biochemical data         less for non-secreting adenomas in our study, with uptake
and MRI results. In two of the patients (N˚ 19 and 25)           in one out of the three patients who showed grade II
with positive SRS, the MRI gave a negative result                uptake and underwent surgical treatment. Oppizzi et al
(Figure 2), and the recurrence was demonstrated by               [18] found uptake in 14 out of 22 patients and Schmidt et al
clinical and biochemical results in follow-up. SRS was           [12] detected uptake in six out of 14 such patients. On the
negative in five patients: the absence of recurrence was          other hand, Duet et al [5] found uptake in five out of five
demonstrated by imaging tests and follow-up in three             patients with non-secreting adenoma. We studied one
cases, whereas in the remaining two patients, recurrence         patient diagnosed with ACTH-secreting adenoma and
was confirmed by imaging (MRI and CT) and the                     detected no uptake, in keeping with several other studies.
evaluation of post-treatment improvements. MRI was               De Herder and coworkers detected no uptake in eight
negative for recurrence in four patients. The absence of         patients with ACTH-secreting adenoma and Stalla et al
recurrence was confirmed in two of them (N˚ 26 and 31).           suggested that the elevated cortisol levels in patients with
   SRS correctly diagnosed 16 of the 18 patients with sus-       ACTH-secreting adenoma may inhibit the expression of
pected recurrence, whereas MRI correctly diagnosed 14 of         somatostatin receptors [20–22].
the 17 patients who had MRI (one patient refused MRI).              Among the patients with confirmed tumour recurrence,
   According to our results, SRS showed the best results in                                                      ¨
                                                                 SRS correctly detected 13 out of 15 patients. Plokinger et al
cases of recurrence of ACTH-secreting tumours (4/5               [8] studied 10 patients after surgery for GH-secreting
patients correctly identified) and non-secreting tumours          pituitary adenoma. Seven of them with tumours associated
(5/7 patients correctly identified).                              with persistent elevation of GH levels were not detected by
   In the present study, scintigraphy with 111In-octreotide      scintigraphy. They concluded that SRS is not useful in
showed uptake in 10 out of 14 patients with confirmed             detecting tumour recurrence in cases with a negative MRI
pituitary tumour and in 13 out of 15 patients with               result. In our study, tumour recurrence was diagnosed by
confirmed recurrence, with an overall sensitivity of 79%.         SRS in 13 patients and two of them had a negative MRI.
                                                                 The diagnosis of recurrence was subsequently confirmed in
                                                                 all cases. Lauriero et al [9] showed uptake in eight of 10
Discussion                                                       patients (4 GH-secreting and 6 PRL-secreting adenomas)
   The presence of high-affinity somatostatin receptors in        diagnosed with tumour recurrence. Both patients in our
most neuroendocrine tumour cells allows the in vivo              study with suspected recurrence of PRL-secreting tumour
scintigraphic visualization of neuroendocrine tumours            showed positive uptake. Out of seven patients in our study
after the intravenous administration of a radiolabelled          with recurrence of non-secreting adenoma, five had
somatostatin analogue. The diagnosis of suspected cases of       positive uptake of octretide, with no false positive cases.
pituitary tumour or pituitary tumour recurrence can be              In the present study, scintigraphy showed good results
based on CT and MRI but the definitive diagnosis depends          in patients with suspected recurrence of ACTH-secreting
on histopathological study following surgery. When               pituitary adenoma, with detection in four out of the five
tumour recurrence is suspected, it can be difficult to            patients. Various authors have studied the presence of
distinguish between residual tumour and scarring asso-           somatostatin receptors in pituitary adenomas and the
ciated with post-surgical changes using CT or MRI [7].           inhibitory effects of somatostatin, including on ACTH-
Scintigraphy with 111In-octreotide allows the visualization      secreting adenomas, with very variable results [23]. Spada
of pituitary tumours on the basis of fundamental                 et al [24] studied the inhibitory effects of somatostatin
characteristics of membrane receptors. Initially, these          in vivo in six patients with ACTH-secreting pituitary
studies used 123I-Tyr3-octreotide to radiolabel somato-          adenoma who underwent transesphenoidal surgery, and all
statin analogues [1, 13–15]. Subsequently, the use of 111In-     showed positive results, implying that these tumours must
DTPA-D-Phe-Octreotide became widespread and iodine               have somatostatin receptors. In contrast, no uptake was
labelling was abandoned. In the present study, scintigra-        shown by receptor scintigraphy in any of the 19 patients
phy with 111In-octreotide showed positive uptake in 10           with Cushing’s disease or eight patients with ACTH-
out of 14 patients with confirmed pituitary tumour and 13         secreting pituitary adenoma in a prospective in vivo study
out of 15 patients with confirmed recurrence, with an             by De Herder et al, although uptake was present in eight
overall sensitivity of 79%. Reports on the sensitivity of this   out of 10 patients with ectopic secretion of ACTH [20].
technique have been variable, ranging from 37% found by          This discrepancy may be due to the long-term exposure of
Schmidt et al [12], who studied 24 patients and obtained         patients with ACTH-secreting adenoma to excessive levels
positive uptake in only nine (9/24), to 88.5% described by       of circulating cortisol. This exposure could negatively
Colao et al [16] in a study of 38 patients with pituitary        influence the expression of somatostatin receptors [20],
adenomas. In our study, the best results were for GH- and        whose presence in these tumours has been confirmed by in
PRL-secreting tumours (7/8), similar to the findings of           vitro studies [6, 22, 24]. The present study demonstrates
Legovini et al [17] and Oppizzi et al [18]. Among our five        there may be a use for SRS in patients with suspected
patients with pituitary tumour that did not secrete GH or        recurrence of ACTH-secreting pituitary adenoma,
PRL, three showed tracer uptake (1 TSH-secreting                 although the sample size was small.
adenoma, 1 LH-secreting adenoma and 1 non-secreting
adenoma). Van Royen et al [19] showed uptake in five out
of six patients with non-GH-secreting pituitary adenoma
(2 non-functioning, 2 TSH-secreting, 1 prolactinoma and 1          SRS, in combination with other imaging modalities, is a
Nelson’s syndrome). In our study, two patients with              useful tool in the diagnosis and follow-up of pituitary

114                                                                          The British Journal of Radiology, February 2005
Somatostatin receptor scintigraphy in pituitary adenomas

tumours. This method allows scar tissue to be differ-                12. Schmidt M, Scheidhauer K, Luyken C, Voth E, Hildebrant
entiated from tumour recurrence after the surgical                       G, Klung N, et al. Somatostatin receptor imaging in
treatment of pituitary adenomas and showed good results                  intracranial tumours. Eur J Nucl Med 1998;25:675–86.
in the detection of recurrence of ACTH-secreting ade-                13. Krenning EP, Bakker WH, Breeman WA, Koper JW, Kooij
                                                                         PP, Ausema L, et al. Localization of endocrine related tumors
noma, although a larger sample size is required to verify
                                                                         with radioionated analogue of somatostatin. Lancet
this finding. SRS identifies patients with presence of
positive receptors for somatostatin, who can then be                 14. Flaglia G, Bazzoni N, Spada A, Arosio M, Ambrosi B,
selected for medical treatment with analogues of soma-                   Spinelli F, et al. In vivo detection of somatostatin receptors in
tostatin.                                                                patients with functionless pituitary adenomas by means of a
                                                                         radioiodinated analog of somatostatin ([123I]SDZ 204-090).
                                                                         J Clin Endocrinol Metab 1991;73:850–6.
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The British Journal of Radiology, February 2005                                                                                       115

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