Download Somatostatine Receptor Scintigraphy (SRS)

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PEPTIDE RECEPTOR IMAGING
 Tumor cells , despite their seemingly uncontrolled
metabolism and growth are in fact modulated by various
endogenously peptides that interact with receptor on the
tumor surface
 Somatostatin
 Tumor necrosis factor
 Angiogenesis factor
 Vasoactive intestinal peptide
Somatostatin
 It is a peptide hormone produced in the
hypothalamus , pituitary gland , gastrointestinal tract
and pancreas
 It acts as a neurotransmitter that inhibits peptide
formation and secretion by neuroendocrine cells.
 Outside the central nervous system its hormone
activities include inhibition of the physiologic and
tumors release of growth hormone , insulin ,
glucagon, gastrin , serotonin and calcitonin
 It also has an antiproliferative effect on tumors.
Somatostatin
 Somatostatin receptors have been identified on
many different cells and tumors of neuroendocrine
origin
 Neuroendocrine cells are derived from the neural
crest and have in common their ability to
synthesize amines from precursors and produce
peptide that act as hormone and neurotransmitter
Tumor with somatostatin receptors fall into
three categories
1- Neuroendocrine Tumors (NETs) such as pituitary
adenoma, gastrinoma ̗ insolinoma
pheochromocytoma, medulary thyroid cancer and
carcinoid
2- CNS tumors : Astrocytomas, menangioma and
neuroblastoma
3- Other tumors, including lymphoma , breast lung
(SCLC) and renal cell cancer
Neuroendocrine Tumors (NETs)
 A unique feature of NETs is their overexpression of
somatostatin receptors on the tumor cells:
 imaging (
 peptide receptor radionuclide therapy (PRRT)
 In the European consensus guidelines of ENETS from
2012, Octreotide Scan is an important part of the
diagnostic work-up of patients with NETs.
 Localization of NETs primary tumors and unknown
metastases in approximately 90% of patients.
Somatostatine Receptor Scintigraphy (SRS)
in Other Tumors: Lymphoma
 can image many other human tumors expressing
somatostatin receptors, including malignant
lymphomas and thymomas.
 The sensitivity of SRS to image somatostatin receptor-
positive tumors is very high
 The sensitivity of somatostatin receptor scintigraphy
for Hodgkin’s lymphoma is 95%-100%, whereas for
non-Hodgkin’s lymphoma it is around 80%.
OCTREOTIDE
 The first available somatostatin analog was octreotide
 Altering small parts of the synthetic peptides readily
changes the binding profile to different receptors:
 Lanreotide
 Pasireotide
 Depreotide
Somatostatin Receptor Scintigraphy (SRS)
Octreotide Scan(OctreoScan)
Normal uptake occurs in the thyroid gland ,liver
gallbladder , spleen , kidneys and bladder
Advantages of Somatostatine
Receptor Imaging (SRI)
 SRI may detect resectable tumors that would
be unrecognized with conventional imaging
technique
 It may prevent surgery in patients with wide
spread metastases
 Clarifying equivocal findings on CT or MRI
 It may direct the choice of therapy in patients
with inoperable tumors
 It used to select patients for PRRT
Normal scintigraphic findings and artifacts
of Octreoscan
 Visualization of thyroid , spleen , liver, kidneys ,
bladder , bowel and in a portion of patients , the
pituitary gland
 False positive :Visualization of thyroid abnormalities ,
accessory spleen , recent CVA , activity at site of recent
surgical incision , diffuse breast uptake in female ,
sarcoidosis and chest uptake after irradiation
Figure 1 illustrates normal, physiological distribution of 99mTc-EDDA/HYNIC-TOC in a
human body. It can clearly be seen that the activity is accumulated mainly in the liver,
spleen, kidneys and urinary bladder and, to a lesser extent, in the thyroid. The low
background in the thoracic region is of particular importance for diagnostic evaluation of
uptake by pulmonary tumours (Figs. 2, 3).
Fig. 4A, B. SPECT studies of the head (sagittal slices).
A Normal uptake of 99mTc-EDDA/HYNIC-TOC in a pituitary gland.
B Substantially enhanced uptake of the radiopharmaceutical in a
growth hormone-secreting pituitary adenoma
Accuracy
 For more neuroendocrine tumors such as
Gastrinoma , Pheochromocytoma Neuroblastoma
and Carcinoid the sensitivity is very high (90%)
 Two exception are Insolinoma and Medullary
thyroid carcinoma (only 50% sensitivity)
 The sensitivity for Lymphoma, Lung and Breast
cancer is about 70%
Hurthle cell
carcinoma remnant
Bilateral carotid bod
paragangliomas
Normal
Sarcoidosis
Skeletal metastases of a
pheochromocytoma
a neck lymphoma
Gastroenteropancreatic tumor
On scintigraphy 24 hours
after injection of 7.4 GBq [177Lu-DOTA0,Tyr3]octreotate liver
metastases were clearly visualized (arrows).
Gastrinoma
Carsinoid tumor
False negative somatostatine scintigraphy
 1- In small primary tumor (<1cm)
 2- Tumors with low somatostatin receptors
False positive
 In areas of inflammation
 Occasionally in nonendocrine tumors.
Somatostatine Receptor Scintigraphy (SRS)
in Lymphoma
 The sensitivity of SRS to image somatostatin receptor-
positive tumors is very high
 The sensitivity of somatostatin receptor scintigraphy
for Hodgkin’s lymphoma is 95%-100%, whereas for
non-Hodgkin’s lymphoma it is around 80%.
Thorax of Patient 5. (A) 4-hr scintigram shows pericardial infiltration (arrows), bulky
mediastinal disease (bold ar row) and a right supraclavicular lymph node (arrow-head).
(B) Corresponding x-ray with mediastinal mass.
Nuclear Medicine in Lymphoma
Gallium Scan
was a cornerstone in functional imaging of lymphoma
However :
- Gallium may not be available
- physicians usually refuse to perform Gallium scan
due to logistic problems
- Several days for imaging
Nuclear Medicine in Lymphoma
FDG-PET
is a promising functional imaging of lymphoma
However :
- may not be available
- Its expensive
Nuclear Medicine in Lymphoma
Somatostatin Receptor Imaging
(Octreotide Scan)
is also a useful functional imaging of lymphoma
-
Available
Reasonable cost (cost effective)
Easy imaging in one day (less than 4 hours)
Labeling with Tc99m: available and cheap
Nuclear Medicine in Lymphoma
Somatostatin Receptor Imaging
(Octreotide Scan+SPECT) : is useful and can be
recommended :
 First: baseline before beginning the treatment
 In follow-up
 For assessment of response to therapy
 For assessment of relapse
Solitary Pulmonary Nodule (SPN)
 SPN radilogically defined as a single lesion that is
<3cm in diameter , surround by lung parenchyma and
without associated adenopathy or atelectasis
 Most SPNs are incidental findings at CXR or CT
 The incidence of malignancy in SPNs range from 10 to
70%
Lung: SPN
 The probability of malignancy is higher in heavy
smokers with hemoptysis , higher age , larger nodule
size or previous malignancy
 The differential diagnosis of an SPN include neoplastic
,inflammatory , vascular traumatic and congenital
lesions and less frequently granulomas and sarcoidosis
SPN continue
 The main concern in a patient with SPN is to reach an
accurate diagnosis of malignancy since an early detection
enables a better prognosis
Tc99m-depreotide (Neotect)
 It is a somatostatin analog that has been approved
specifically for detection of lung cancer in patients with
pulmonary nodule (Approved by FDA for imaging of
lung masses seen on CXR or CT)
 Many lung tumors express SS receptors to a greater
extent than normal tissue
 To confirm pulmonary malignancy of a lung mass and
for clinical staging.
 Because of the relatively high background activity and
short half life of the tracer ,it is less suited for the
detection of abdominal neuroendocrine tumor
Tc99m-Depreotide
 The accuracy of Depreotide in evaluation of
indeterminate pulmonary nodules appears to be
comparable to FDG PET (sensitivity 95% and
specificity 85%)
There has really been only one large published study with this
radiopharmaceutical that looked at 114 indeterminate lung nodules the smallest
ranged down to 0.8 centimeter, and that was a benign lesion. Imaging was done
both with planar scintigraphy, as well as SPECT. All the lesions were confirmed by a
biopsy. The sensitivity was 97% with false negative results in two primary
adenocarcinomas, and one metastatic adenocarcinoma, while all of these lesions
were under 2 centimeters. I think the smallest was 1.1 centimeter. Specificity has
not been quite as good, however, with a specificity of only 73%. And the false
positives were largely related to granulomas, which has been the bane of most of
the nuclear medicine approaches, and one hamartoma. The explanation for that is
not at all clear. Just a couple of quick examples from the published multicenter
study. Here is a fairly good sized adenocarcinoma, which is easily seen on the
SPECT image.
V.R.Dabbagh; DSNMC;
www.DSNMC.ir