● 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

• t_phys= 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)