Definition & Overview

Radiopharmaceutical localisation of tumour or the distribution of radiopharmaceutical agents to locate a tumour is a diagnostic procedure used to detect cancerous growths in the body. It is categorised under nuclear medicine and uses molecular imaging methods and radiopharmaceutical drugs.

The use of radiopharmaceuticals is slowly gaining recognition in the field of medicine. It is now being used to diagnose and treat several serious medical conditions. Radiopharmaceuticals are substances that target certain organs in the body and are designed based on the target organ’s physiological function.

Who Should Undergo and Expected Results

The procedure is beneficial for patients who are suspected of having a tumour.

Tumours are abnormal growths of tissue that can form in any part of the body. They can be internal and can cause external swelling or inflammation. Some tumours are malignant or cancerous, while some are benign (non-cancerous). They are also referred to as mass or neoplasm.

Tumours can cause a wide range of symptoms, such as:

  • Pain
  • Unexplained nausea
  • Loss of sensation
  • Unexplained vomiting
  • Fever
  • Fatigue
  • Unexplained weight loss


The symptoms may also differ depending on the tumour's location. For example, a tumour on the brain may cause:

  • Headaches
  • Vision problems
  • Balance problems
  • Speech difficulties
  • Behavioural changes
  • Seizures
  • Hearing problems


These symptoms usually become noticeable when the tumour grows large enough to push on nearby organs, nerves, and blood vessels. If they grow slowly or are in places where they do not affect any organs, nerves, and blood vessels, the patient may not experience any symptoms at first. This usually leads to a delayed diagnosis.

Unfortunately, a delayed cancer diagnosis can make a crucial difference in the survival or prognosis of the patient. This is because cancer treatment works best when it begins at the early stages of the disease. Radiopharmaceutical localisation of a tumour can help doctors locate abnormal growths even in early stages.

How is the Procedure Performed?

Radiopharmaceutical localisation of tumour works in several ways, including:

  • Active transport – This involves moving radiopharmaceutical agents through normally operative metabolic pathways in the body. This is effective in detecting thyroid tumours.
  • Phagocytosis – This is performed through the physical entrapment of colloidal particles by Kupffer cells in the reticuloendothelial system. This is effective in detecting tumours that affect the liver and spleen.
  • Capillary blockade – This is performed through the intentional microembolisation of a capillary bed. The procedure is also known as pulmonary perfusion imaging.
  • Cell sequestration – This works by injecting damaged red blood cells to scan the liver and spleen.
  • Simple/exchange diffusion – This works by injecting a radiotracer across cell membranes for diffusion. The radiotracer then binds or attaches to a component of the cell.
  • Compartmental localisation – This works by injecting a radiotracer and performing an imaging on a specific fluid space.
  • Chemisorption – This works by allowing a radiopharmaceutical to bind to the surface of a solid absorption.
  • Antigen/antibody reaction – This is an uptake at the tumour site caused by the binding of the radiopharmaceutical agent to the tumour. This is effective in diagnosing ovarian and colorectal carcinoma.
  • Receptor-binding – This works by allowing a radiopharmaceutical to bind to high-affinity receptor sites.


The distribution of radiopharmaceutical agents, on the other hand, is performed through:

  • Intravenous injections
  • Ingestion
  • Inhalation


The use of radiopharmaceuticals and nuclear medicine imaging can produce four different types of images, namely:

  • Planar (static) – This is a static two-dimensional view that displays only one image at a time.
  • Dynamic – This refers to a series of images that captures movement and activity within the body, such as the flow of blood to any organ.
  • Single photon emission computed tomography – Also known as SPECT, this offers a three-dimensional view of the organ being examined.
  • Whole body view – This provides two-dimensional front and back views of the body.

Possible Risks and Complications

Localising tumours using radiopharmaceuticals is generally a safe procedure. Although there are risks involved with the use of radiopharmaceuticals, these are considered less significant compared to the risks of surgical tumour localisation through a biopsy.

The following are some of the risks associated with radiopharmaceutical use:

  • Lower white blood cell count
  • Lower platelet count
  • Radiation exposure


The amount of radiation exposure during a radiopharmaceutical localisation of a tumour, however, is not a significant cause for concern. This is because the amount of radiation is fairly small and does not differ from the amounts used during other radiation treatments.

References:

  • Franc BL, Cho SY, Rosenthal SA, Cui Y, Tsui B, Vandewalker KM, Holz AL, Poonamallee U, Pomper MG, James RB. “Detection and localization of carcinoma within the prostate using high resolution transrectal gamma imaging of monoclonal antibody directed at prostate specific membrane antigen (PSMA) – proof of concept and initial imaging results.” Eur J Radiol. 2013 Nov; 82(11): 1877-84. https://www.ncbi.nlm.nih.gov/pubmed/23993140

  • Ting G, Chang CH, Wang HE. “Cancer nanotargeted radiopharmaceuticals for tumor imaging and therapy.” Anticancer Res. 2009 Oct; 29(10): 4107-18. https://www.ncbi.nlm.nih.gov/pubmed/19846958

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