2 HRS SNM/VOICE CEU
 

 


IMAGING OF NEUROENDOCRINE TUMORS: 111In Octreotide


● PATIENT INDICATIONS

111In Octreotide is indicated for the scintigraphic localization of primary and metastatic neuroendocrine tumors bearing somatostatin receptors.


● TUMOR TYPES IMAGED

TUMOR TYPES IMAGED
Neuroblastomas
Pheochromocytomas
Paraganglioma
Carcinoid Tumors
Medullary Thyroid Ca
VIPoma
Insulinomas
Gastrinomas
Pituitary Adenoma
Glucagonoma
Islet Cell Carcinomas
Small Cell Lung Ca


● CHARACTERISTICS OF 111In

  • tphys= 2.805 d= 67.32 hr
  • 171.3 keV gamma: 90.2 % abundance
  • 245.4 keV gamma: 94.0 % abundance

● RADIOTRACER USED

3-6 mCi of high purity 111InCl3 in dilute HCl in a 10 ml vial

● RADIOCHEMICAL REACTION

In3+ + DTPA-Octreotide -------------> In DTPA-octreotide

final pH: 3.8-4.3

● BASIC LABELING THEORY

DTPA group is covalently bonded to Octreotide molecule 111In actually bonds to DTPA portion of molecule, not to octreotide
molecular structure

● MOLECULAR STRUCTURE OF OCTREOTIDE

● PATIENT PREPARATIONS

■ Patient must be very well hydrated before the dose and for up to 48 hr afterward to minimize radiation dose
■ Patient must take a mild laxative the evening before administration of the drug and continue for 2 days.

● ADMINISTERED DOSE

■ For Planar/pediatric imaging: 3 mCi = 111 MBq
■ For SPECT imaging: 6 mCi = 222 MBq
■ Must perform visual inspection to insure absence of particulates

● CONTRAINDICATIONS

Sensitivity to somatostatin and its analogues

● ADVERSE REACTIONS OCCURRING IN <1% OF ALL PATIENTS

  • dizziness
  • fever
  • flushing
  • headache
  • hypotension
  • increased liver enzymes
  • jointpain
  • nausea
  • sweating
  • weakness

OCCURRING IN <3% OF ALL PATIENTS

  • diarrhea and vomiting
  • abdominal
  • pain/discomfort
  • injection site pain

● CLINICAL PHARMACOLOGY

  • Pentetreotide is a long acting analog of the hormone somatostatin
  • The 111In complex binds avidly to somatostatin receptors throughout the body.
  • Initially concentrates in Plasma.
  • Within 1 hr, most of the 111In octreotide distributes to extravascular body tissues and in tumors containing a high density of somatostatin receptors.
  • After background clearance via the kidneys, visualization of somatostatin rich receptors is achieved.
  • t 1/2 of clearance from blood is 7-8 min
  • By 20 hr post injection, <1% of 111In activity remains in blood.
  • Whole body biological half-life of 111In Octreotide is 6 hr

● NORMAL DISTRIBUTION OF 111In-Octreoscan

■ Normal pituitary gland
■ thyroid gland
■ liver
■ spleen
■ kidneys
■ urinary bladder
■ bowel (occasionally)

● RADIATION DOSIMETRY

ORGAN
RADS / 6 mCi
KIDNEYS
10.8
LIVER
2.4
SPLEEN
14.8
BONE MARROW
0.7
BLADDER WALL
6.1
STOMACH WALL
1.1
UPPER GI
1.2
LOWER GI
1.6
ADRENALS
1.5
THYROID
1.5

 


● CLINICAL IMPACT OF OCTREOSCAN IMAGING

■ Yielded information about localizations not previously identified: 27.9% (57/104)
■ Demonstrated uptake in lesions known to exist, but not verified as neuroendocrine tumors 28.2% (55/195)
■ Localized neuroendocrine tumors in patients with clinical and hormonal evidence of tumor, but no prior localizations 37.5% (21/56)
■ Produced a change in patient management-31.1% (64/206)












 
 

 


 

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February 13, 2010