12. HOW IS MELANOMA MONITORED?

Patients who have been diagnosed with a primary melanoma are advised to be carefully monitored for at least 5 years.  Patients are examined for evidence of local spread (a lump in the vicinity of the tumour) and any enlargement of the lymph gland. It is almost impossible to detect evidence of haematogeneous spread unless the patient develops symptoms. 

For some cancers tumour markers or biomarkers are found in the blood and help indicate the presence or extent of a particular cancer.  Tumour markers work by measuring the level of a chemical, usually a protein, produced by cancer cells. Unfortunately for melanoma no such blood markers exist and therefore the extent of the disease must be measured using a combination of physical examinations and various radiology techniques.  The major types of physical examinations and radiology techniques undertaken are explained below:

Physical examination

As melanoma quite often reappears in the lymph glands a physical examination of these glands to determine whether enlargement has taken place is an essential part of melanoma monitoring.  The major sites of lymph glands are; under the arms, in the groin and on the neck.  These sites are illustrated in the picture below:

Computerised Tomography (CT or CAT scan)

A computerised Tomography is a large donut shaped machine that produces two-dimensional pictures of various parts of a patient's body.  It uses radiation to detect internal tumours and provides a more detailed image than a one-dimensional X-ray.

Magnetic Resonance imaging (MRI)

An MRI uses radio waves and a magnetic field to create an image of internal body parts.  An MRI doesn't use radiation in creating these images and as a result is generally considered to have a lower risk of adverse side effects.  

Positron Emission Tomography (PET scan)

A PET scan is a nuclear scanning technique, used to detect deposits of cancer cells.  It has the advantage of being able to identify tumours that are too small to show up on either an MRI or CT scan.  A PET scan requires the intravenous injection of a radioactive tracer which seeks out and highlights cancer cells due to their different metabolic processes.  A PET scan has two distinct stages. The first stage involves an intravenous injection of the radioactive tracer, followed by a period of stillness and rest while the substance moves through the body.  The second stage is the actual scanning during which the patient is moved through a large cylinder shaped mechanism.

Bone-Scan

A bone scan is another nuclear medicine test that is used to detect the presence of cancer cells in the bones.  It is administered in much the same way as a PET scan and involves the injection of a radioactive tracer, followed by a scan that helps indicate the presence of cancer in the bones of the patient.