Although tumour markers are extremely useful in determining whether a tumor is responding to treatment or assessing whether it has recurred, no tumor marker identified to date is sufficiently sensitive or specific to be used on its own to screen for cancer. A tumour marker is a substance that is produced by the body in response to cancer, or is produced by the cancer cell itself. itself. Sometimes, these markers are specific to one type of cancer only, while others may not and can be seen in different types of cancer. The substances are usually found to be very high levels in the blood or urine or body tissue for individuals with confirmed cancer. Learn more about this from Dr Verna Lee Kar Mun, Family Medicine Specialist and Head of IMU Healthcare Medical Clinic at Cancer Marker Tests – Are They Accurate? (InfoMed, Oct-Dec 2017).