Intraoperative Hand Held Gamma Probe Detection

Robert M Van Haren
1
, Timothy L Fitzgerald
2,3
1
College of Human Medicine, Michigan State University. Lansing, MI, USA.
2
Department of
Surgical Oncology, Richard J Lack Cancer Center at Saint Mary’s Mercy Medical Center.
Grand Rapids, MI, USA.
3
Division of Surgical Oncology, East Carolina University Brody
School of Medicine. Greenville, NC, USA
ABSTRACT
Context The advantage of intraoperative
gamma probe detection with
111
In-DPTA-
octreotide radiotracer has previously been
demonstrated in functional neuroendocrine
tumors. We report the only known case of a
recurrent
nonfunctional
pancreatic
neuroendocrine
neoplasm
localized
intraoperatively using this radiotracer and a
hand held gamma probe.
Case report A 51-year-old woman was found
to have a recurrence 23 months after
laparoscopic
distal
pancreatectomy,
splenectomy and wedge resection of a liver
metastasis
for
a
non-functional
neuroendocirne neoplasm of the pancreas. CT
scan and
111
In-DPTA-octreotide scan
displayed two lesions in the right lobe of the
liver and a third area of increased isotope
uptake adjacent to kidney and pancreas. A
single liver lesion was seen on CT. There
were concerns regarding the ability to localize
the lesion in the upper abdomen. In order to
facilitate identification the patient was
injected
with
111
In-DPTA-octreotide
preoperatively and intraoperatively a gamma
probe was used to identify two lymph node
posterior to the pancreas, only one of which
could be palpated.
Conclusion In this case the technique of
preoperative injection with octreotide
radiotracer and intraoperative hand held
gamma probe successfully localized a
nonfunctional neuroendocrine tumor that CT
scan and intraoperative exploration failed to
identify.
INTRODUCTION
Neuroendocrine tumors can be difficult to
localize with conventional imaging such as
CT scan, ultrasound (US), or MRI. Single
photon emission computed tomography
(SPECT) imaging with
111
In-DPTA-octreotide
radiotracer can be helpful in localization of
primary and secondary neuroendocrine
tumors. A natural extension of this technique
is intraoperative localization with a hand held
gamma probe similar to sentinel lymph node
biopsy, minimally invasive parathyroid, and
radioimmune guided surgery. This approach
has been successfully applied to functional
pancreatic neuroendocrine tumors. We report
the only known case of a nonfunctional
pancreatic neuroendocrine tumor localized
intraoperatively using
111
In-DPTA-octreotide
radiotracer and a hand held gamma probe.
CASE REPORT
A 51-year-old woman presented with dull,
deep left abdominal pain, and mild fevers. CT
scan identified a cystic neoplasm in the tail of
the pancreas, measuring 38 mm in diameter.
A hepatic lesion most consistent with a

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JOP. J Pancreas (Online) 2008; 9(6):704-707.
JOP. Journal of the Pancreas - http://www.joplink.net - Vol. 9, No. 6 - November 2008. [ISSN 1590-8577]
705
cavernous hemangioma was also visualized
on CT scan. Subsequent, endoscopic
ultrasound (EUS) demonstrated a solid, round
lesion suspicious for a neuroendocrine tumor.
The patient underwent a laparoscopic distal
pancreatectomy with splenectomy, and
intraoperatively she was noted to have one
left lateral segment liver lesion that was
treated with wedge resection. The surgical
pathology revealed a 4.5 cm pancreatic
nonfunctional neuroendocrine neoplasm with
moderate atypia, 2/9 metastatic lymph nodes,
and an isolated hepatic metastasis. The patient
tolerated the procedure well and was followed
with routine pancreatic polypeptide and
chromogranin A.
Twenty three months after initial surgery,
multiple metastases were noted. CT scan
displayed a vascular lesion with increased
size (from 16x10 mm to 21x17 mm) in the
right lobe of the liver that was suspicious for
metastasis (Figure 1).
111
In-DPTA-octreotide
scan demonstrated two lesions in the anterior
and inferior right lobes of the liver, only one
of which was seen on CT, and a third area of
increased isotope uptake adjacent to the
superior pole of the kidney and posterior to
the pancreas. Chromogranin A and pancreatic
polypeptide, 26 ng/mL (reference range: 2-18
ng/mL) and 334 pg/mL (reference range: 0-
290 pg/mL), respectively, both increased to
abnormal range supporting the diagnosis of
recurrence.
Right hepatic resection was planned, however
there were concerns regarding the ability to
localize the lesion in the upper abdomen. In
order to facilitate identification the patient
was injected with 3.6 millicuries of
111
In-
DPTA-octreotide 24 hours preoperatively.
Intraoperatively a Navigator probe
TM
(MIPS
Technologies, Mountian View, CA, USA)
was used to identify regions of increase tracer
uptake. Identification was hindered by high
background counts, particularly in the kidney.
However, an area of clear increased uptake
was noted posterior to the pancreas
corresponding to SPECT scan images. An
additional lymph node was identified
medially with increased activity when
compared to the background. After excision
an ex vivo ten second count was performed
and compared to the abdominal background
counts and both lymph nodes had
significantly increased signals. The first
lymph node was palpable and enlarged but the
second had normal dimensions. Because the
patient was high risk for additional celiac
lymph node disease a complete celiac artery
lymphadenectomy was performed; 19
additional lymph nodes were obtained, none
of which had metastatic disease. Of note ex
vivo counts of this tissue demonstrated no
tracer uptake. The final surgical pathology
demonstrated 2 right hepatic lesions, and 3/22
lymph nodes involved metastases.
Post-operatively patient was followed with
periodic CT,
111
In-DPTA-octreotide scan, and
laboratory studies (chromogranin A and
pancreatic polypeptide). Fifteen months after
the second surgery,
111
In-DPTA-octreotide
with SPECT imaging revealed an abnormal
focus of radiotracer uptake within in the
central portion of the residual liver that was
not visualized on CT scan. MR imaging
correlated to the
111
In-DPTA-octreotide scan
with a small area (10 mm) of enhancement
just lateral to the bifurcation of the portal vein
and patient underwent complex wedge
resection of this segment 4a/b lesion.
DISCUSSION
Neuroendocrine tumors typically arise from
the pancreatic islets of Langherans, and are
also known as islet cell tumors. They are rare
Figure 1. CT scan and 111In-DPTA single photon
emission computed tomography (SPECT) scan. Liver
and extrahepatic metastasis are denoted by arrows.

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JOP. J Pancreas (Online) 2008; 9(6):704-707.
JOP. Journal of the Pancreas - http://www.joplink.net - Vol. 9, No. 6 - November 2008. [ISSN 1590-8577]
706
tumors, with an incidence of 1-2/100,000
cases per year. Pancreatic neuroendocrine
tumors are divided into two groups:
functional and nonfunctional. Functional
tumors are often discovered secondary to
symptoms of the active hormone such as:
insulin, glucagon, somatostatin, growth
hormone releasing factors, adrenocortico-
trophic hormone (ACTH), vasoactive
intestinal peptide (VIP), or gastrin.
Nonfunctional neoplasms are identified by
local tumor mass effects, vague abdominal
pain, or incidentally on imaging. Increasing
use and quality of abdominal imaging has
lead to increased identification of
asymptomatic neoplasms such as kidney,
liver, and pancreatic lesions [1, 2, 3]. There
are several reports of pancreatic
“incidentalomas” in the literature [4, 5, 6].
Many of these incidentalomas are
nonfunctional neuroendocrine neoplasms.
Surgery is the mainstay of treatment for
neuroendocrine tumors, and the only curative
therapy.
A variety of imaging studies can be used for
tumor staging and localization of
neuroendocrine tumors such as CT scan,
MRI, EUS, and myocardial
123
I-metaiodo-
benzylguanidine (MIBG) [7]Although, as
was evident in our case, imaging techniques
such as CT scan, EUS, and MRI can fail to
localize neuroendocrine tumors. This failure
has also been reported for functional
neuroendocrine tumors such as insulinomas
where 40% of cases are not visualized by
conventional imaging [8].
SPECT
111
In-DTPA-octreotide scans utilize
tumor receptor binding of radio labeled
isotopes to somatostatin receptors to localize
these neoplasms. Somatostatin is a natural
peptide hormone secreted by the digestive
system and many other sites of the body. Five
cell membrane receptors (somatostatin
receptors 1-5) are responsible for cellular
functions including inhibition of cell
proliferation (somatostatin receptors 1 and 2),
apoptosis (somatostatin receptor 3), and
antimitotic effects (somatostatin receptor 5).
Octreotide, a somatostatin analog, has been
effective in inhibiting hormone secretion by
targeting these somatostatin receptors and
thus controlling hormone related symptoms
[9].
SPECT
111
In-DTPA-octreotide scan is
superior to CT, MRI, angiography, and EUS
for identifying islet cell neoplasms, carcinoid
and their metastases; with a sensitivity of 82-
95% [10]. A natural extension of this
technique is intraoperative localization with
hand held gamma probe. This is currently
employed in clinical practice with sentinel
lymph node biopsy and minimally invasive
parathyroid surgery. Radioimmune guided
surgery has been described for localizing
primary or metastatic colorectal cancer,
medullary thyroid carcinoma, and
insulinomas [11, 12]. The superiority of
intraoperative gamma probe detection was
reported in a study of gastro-entero-pancreatic
neuroendocrine (carcinoid) neoplasms.
Seventy somatostatin receptor positive lesions
were localized by intraoperative gamma
probe. Only 74% of these lesions were
visualized on preoperative receptor imaging,
44% were localized by surgical palpation, and
43% by other radiological techniques.
Additionally, intraoperative gamma probe
localized smaller lesions (6 mm) as compared
to surgical palpation (10 mm) [12].
In the presented case the modified
radioimmune guided surgery technique
allowed identification of pathologic lymph
nodes that were radiologically but not
clinically obvious. One lymph node was
palpable and could possibly have been
identified with some difficulty by manual
exploration; the second would not have been
detected in this manner. Identification was
somewhat difficult secondary to high
background counts, but there was a clear
distinction confirmed with ex vivo counts.
In conclusion, the use of
111
In-DPTA-
octreotide radiotracer and intraoperative hand
held gamma probe can be used to localize
nonfunctional neuroendocrine metastases that
are not seen on imaging or that would be
difficult to localize with traditional surgical
exploration. This tumor localization technique
was shown to be superior to CT scan and
SPECT imaging in our patient’s case.

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JOP. J Pancreas (Online) 2008; 9(6):704-707.
JOP. Journal of the Pancreas - http://www.joplink.net - Vol. 9, No. 6 - November 2008. [ISSN 1590-8577]
707
Received June 10
th
, 2000 - Accepted August
17
th
, 2008
Keywords Octreotide; Pancreas; Surgery;
Tomography, Emission-Computed, Single-
Photon
Abbreviation
SPECT: single photon
emission computed tomography
Conflict of interest The authors have no
potential conflicts of interest
Correspondence
Timothy L Fitzgerald
Division of Surgical Oncology
Brody School of Medicine
600 Moye Blvd
Greeenville, NC
USA 27834
 
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