Procedures Tumor Infection Part 5

Somatostatin and Octreoscan Imaging

  • Somatostatin: Hormones released by endocrine and nerve cells found in various organs.

  • Indium 111 Pentetreotide: Known as Octreoscan, a somatostatin analog used to accumulate in neuroendocrine tumors.

Neuroendocrine Tumors

  • Common locations:

    • Pituitary gland

    • Thyroid

    • Pancreatic islet cells

Indications for Octreoscan

  • Purpose: Locate neuroendocrine tumors.

  • Procedure:

    • Inject 5 millicuries of Indium 111 Octreoscan.

    • No patient prep required.

Imaging Procedure

  • 4 hours post-injection: Take anterior and posterior planar images.

  • Patient returns the following day for:

    • Same anterior and posterior images.

    • SPECT imaging.

  • Abnormal result: Indicates abnormal accumulation in pituitary, pancreatic islet cells, or thyroid, identifying a positive Octreoscan.

Imaging Example

  • Positive Octreoscan shown by abnormal imaging indicating pancreatic islet cells.

Monoclonal Antibody Imaging (Moabs)

  • Monoclonal antibodies (Moabs): Labeled to radionuclide for targeting specific antigens in tumors.

  • CEA Scan (Carcinoembryonic Antigen):

    • Uses Indium 111 or Technetium 99m; labeled to artisumab.

    • Commonly used for colorectal cancer imaging.

  • Indium 111 Prostasent: Used for prostate cancer (based on capromab pendetide).

  • Indium 111 Oncocent: Used for ovarian and colon cancer (based on satumumab pentetide).

Indications for Monoclonal Antibody Imaging

  • Purpose: Localize tumor containing specific antigens.

  • Radiopharmaceutical dosage:

    • Indium 111: 5 millicuries.

    • Technetium 99m: 20 millicuries.

    • No patient prep required.

Imaging Procedure for Moabs

  • Injected via IV, images taken at 4 and 24 hours.

  • Depending on the radionuclide used, imaging may extend up to 48 hours.

  • SPECT imaging commonly performed at 24 hours for accuracy.

  • Abnormal image: Increased focal uptake indicating potential tumor presence.

Case Studies

  • Patient Case #1: CEA Scan for Colorectal Cancer

    • 5 millicuries of Indium 111 artisumab injected.

    • Anterior whole-body images taken at 4 and 24 hours.

    • Findings: Abnormal focal uptake in the pelvis, indicating colorectal cancer.

  • Patient Case #2: Prostascent Scan for Prostate Cancer METS

    • 5 millicuries of Prostascent injected.

    • Anterior images taken at 24 hours.

    • Findings: Hot spots in the liver and bone marrow identified as normal; however, noticeable abnormal uptake indicates prostate cancer METS.

Somatostatin and Octreoscan Imaging

Somatostatin

Somatostatin is a peptide hormone that is released by various endocrine and nerve cells and is found in multiple organs including the pancreas, hypothalamus, and gastrointestinal tract. It plays a crucial role in regulating the endocrine system and inhibiting the secretion of other hormones, thus helping to control various bodily functions such as glucose metabolism and digestive processes.

Indium 111 Pentetreotide (Octreoscan)

Indium 111 Pentetreotide, commonly referred to as Octreoscan, is a synthetic somatostatin analog that is primarily used for imaging neuroendocrine tumors. It has a high affinity for somatostatin receptors, which are abundant in certain tumors, allowing it to accumulate selectively in these malignancies, thus making it invaluable for diagnosis and treatment planning. The imaging modality leverages gamma radiation emitted from the Indium 111 isotope.

Neuroendocrine Tumors

Neuroendocrine tumors (NETs) can arise from neuroendocrine cells located throughout the body, with common locations including:

  • Pituitary Gland: Produces hormones that control various bodily functions.

  • Thyroid: Regulates metabolism and growth.

  • Pancreatic Islet Cells: Involved in the regulation of blood glucose levels.

  • Gastrointestinal Tract: Can lead to tumors that secrete hormones affecting digestion and metabolism.

Indications for Octreoscan

Purpose: The main purpose of the Octreoscan is to locate neuroendocrine tumors that may not be detected by conventional imaging techniques. It helps in determining the presence, location, and extent of such tumors.

Procedure:

  1. Injection: 5 millicuries of Indium 111 Octreoscan is injected intravenously without the need for prior patient preparation.

  2. Imaging Procedure:

    • Four hours post-injection, anterior and posterior planar images are taken.

    • The patient returns the following day for additional imaging, including the same anterior and posterior images, followed by SPECT (Single Photon Emission Computed Tomography) imaging, which provides more detailed information.

  3. Abnormal Result Interpretation: An abnormal result indicates abnormal accumulation of the tracer in areas such as the pituitary gland, pancreatic islet cells, or thyroid, identifying a positive Octreoscan that suggests the presence of tumors.

Imaging Example

A positive Octreoscan can be visualized by abnormal imaging results indicating the presence of neuroendocrine tumors, particularly in pancreatic islet cells.

Monoclonal Antibody Imaging (Moabs)

Monoclonal antibodies (Moabs) are engineered antibodies labeled with a radionuclide that can target specific antigens expressed by tumors. This form of imaging allows for precise localization of tumors based on the biological characteristics of the tumor cells.

CEA Scan (Carcinoembryonic Antigen)

The CEA scan uses Indium 111 or Technetium 99m labels combined with artisumab to image tumors that overexpress carcinoembryonic antigens, commonly associated with colorectal cancer and other malignancies.

Other Moabs:

  • Indium 111 Prostascent: Used specifically for imaging prostate cancer based on the specific antigen capromab pendetide.

  • Indium 111 Oncocent: Targeted for ovarian and colon cancers utilizing the antibody satumumab pentetide.

Indications for Monoclonal Antibody Imaging

Purpose: Localize tumors that contain specific antigens, aiding in both diagnosis and therapeutic planning.

Radiopharmaceutical Dosage:

  • Indium 111: 5 millicuries.

  • Technetium 99m: 20 millicuries.

Imaging Procedure for Moabs:

  1. Injection: Administered via IV, with imaging typically performed at intervals of 4 and 24 hours after injection.

  2. Extended Imaging: Depending on the radionuclide utilized, imaging may extend up to 48 hours post-injection, with SPECT imaging commonly performed at the 24-hour mark for added accuracy.

  3. Abnormal Image Interpretation: An abnormal image is characterized by increased focal uptake suggesting the potential presence of tumors.

Case Studies

Patient Case #1: CEA Scan for Colorectal Cancer

  • Procedure: 5 millicuries of Indium 111 artisumab were injected, followed by anterior whole-body images taken at both 4 and 24 hours.

  • Findings: The imaging demonstrated abnormal focal uptake in the pelvic region, correlating with the diagnosis of colorectal cancer.

Patient Case #2: Prostascent Scan for Prostate Cancer METS

  • Procedure: 5 millicuries of Prostascent were injected, with anterior images taken at 24 hours post-infusion.

  • Findings: Images revealed notable hot spots in the liver and bone marrow that were deemed normal, along with significant abnormal uptake suggesting the presence of metastatic prostate cancer.