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Important Background Information (Detail)

Personalized Medicine & You

Important Background Information

We have provided a brief overview of the terms and science surrounding those terms for those people who want more depth.

Tumor markers:

Tumor markers (also called biomarkers) are substances found in the blood, urine, stool, or tissue that are produced by cancer cells. Tumor markers may indicate or suggest the presence of cancer. Different tumor markers may be present for different types of cancer.

The ideal marker would be a blood test for cancer in which a positive result would only occur only if there were a cancer present. This ideal marker would also indicate the stage of the cancer and possible response to treatment. In addition, it, would be easy to measure.


Tumor markers can be used for several purposes:
  • Screening a health population or a high-risk population for the presence of cancer
  • Making an early diagnosis of a specific type of cancer
  • Determining the probable outcome of a patient’s disease
  • Monitoring a patient during the course of surgery, radiation therapy, or chemotherapy
  • Monitoring a patient in remission
Image provided by CISN archives. All rights reserved.

No current test meets all these requirements. Most tests today have problems with false positive and false negative results. For more information about this click here:

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Cancer 101

Tumor markers can be classified into two groups:

  1. Cancer-specific markers are related to a particular type of cancer. The
    tumor itself produces the marker. Cancer-specific markers can be useful
    in the follow-up of treated patients to track progress of the disease or
    response to treatment. Examples include:

    a. CEA (which may be used to monitor patients treated for colorectal

    b. CA19-9 (initially developed used in colon cancer, but found to be
    very sensitive for pancreatic cancer)

    c. CA-125 (a marker that may be used to monitor women with the
    most common type of ovarian cancer during and after active

  2. Tissue-specific markers are related to specific tissue. Elevated levels may
    suggest abnormalities of specific tissue, such as the presence of cancer. An
    example is:

    a. PSA, which may be elevated in the blood when there is noncancerous
    prostate growth or with prostate cancer. In addition, PSA
    also tends to be elevated in older men and in cases where there is
    inflammation or infection of the prostate.

Tumor markers are not always reliable for the following reasons:

  • Normal cells as well as cancer cells can make most tumor markers.
  • Tumor markers may also be associated with noncancerous conditions.
  • Tumor markers are not always present in early-stage disease.
  • People with cancer may never have elevated tumor markers.
  • Even when tumor marker levels are high, cancer may not be present.
  • Tumor markers that may be helpful in monitoring some cancer patients during and after treatment most often are not reliable in detecting cancer.

Because abnormal tumor marker levels may only suggest the presence of cancer, other scientific tests are usually required before confirming a cancer diagnosis.


Genetics is the science of genes and the transmission and variation of inherited traits— in other words, the process by which parents may pass certain genetic traits to their children. Characteristics determined by genes range from eye color, hair color, and height to inheritance of or predisposition for specific diseases.

”Genome” refers to an organism’s complete set of DNA, including all of its genes. In humans, a copy of the entire genome - which is more than 3 billion DNA base pairs – is contained in every cell that has a nucleus.


Genomics is the study of a person’s complete DNA sequence - including genes and “noncoding” DNA segments in the chromosomes and how those genes interact with each other, as well as the internal and external environments they are exposed to.

This includes the study of gene mutations, both those that are passed from parents to children (inherited) and those that happen during your lifetime (somatic). It is these mutations that contribute to the development and spread of cancer.



Pharmacogenetics is a specialty field within the study of genomics. It is generally regarded as the study of genetic variation that can affect an individual’s responses to certain drugs. Pharmacogenetics uses information about a person's genetic makeup, or genome, to help determine the drugs that are likely to work best for that particular person and/or that may be likely to lead to certain adverse effects.

For certain drugs, pharmacogenetics may help to determine whether patients are rapid or slow metabolizers (referring to how long the drug stays in your body) as well as whether they are responders or non-responders (meaning whether the drug works for you).

Having the ability to predict a person’s individual response to a drug, both in terms of therapy benefit and the likelihood for adverse events, will play a crucial role in:

  • Preventing the use of a drug that is likely to cause serious effects for a particular patient without benefit
  • Guiding the selection of optimal therapies that are most likely to benefit a specific patient

Deaths from drug side effects are one of the top ten leading causes of death, so this field is very important.


For decades, scientists and doctors assumed that cancer was caused by irreversible damage to some critical stretch of DNA within one's genome. But in the last few years, a much more complex picture has emerged, one that shows that some cancers are caused by epigenetic changes-tiny chemical tags that accumulate over time and can turn genes on or off rather than mutate them.

The word "epigenetic" literally means "in addition to changes in genetic sequence." It is used to refer to any process that alters gene activity without changing mutating the DNA sequence. Experiments show that epigenetic changes, unlike mutations, can be reversed.


Proteomics is the study of the structure, functions, and interactions of proteins. While genes are the “recipe” of the cell, containing all the instructions for assembly, proteins are the products of these recipes, functioning as the cellular engines that drive both normal and disease physiology.


Proteomics is much more complicated than genomics. While an organism’s genome is more or less constant, the proteome - or set of proteins expressed by the genome - differs from cell to cell and from minute to minute, depending on the activity of specific genes.

This makes interpreting protein measurements very difficult.

Image Courtesy of U.S. Human Genome Project

A breakthrough in cancer treatment was the discovery that tumors “leak” proteins and other molecules into blood, urine, and other accessible body fluids. The greatest promise for the early detection and treatment of cancer is to collect such fluids from patients and test them for the presence of cancer-related molecules, called cancer biomarkers or tumor markers.

Although protein biomarkers hold great promise, there are significant challenges to consider:
  • The vast number of proteins that exist in the body can make it difficult to identify and describe them.
  • Proteins are continually moving and undergoing changes.
  • Proteins exist in a wide range of concentration in the body.
  • Lack of standardization – Laboratories across the county collect, store, and study proteins in different ways. This lack of standardization makes it difficult to accurately compare results from one laboratory to another.


Metabolomics is the systematic study of the unique chemical fingerprints that cells leave behind. More specifically, it is the study of how your body responds to drugs, environmental changes and diseases. Metabolomics is an extension of genomics (study of genes) and proteomics (study of proteins).

If metabolomic information could be translated into better diagnostic tests, it might have the potential to impact clinical practice, and it might lead to more targeted biomarkers that improves care.


If you move from the top of the image to the bottom you get more precise information on what is happening in your body. So metabolites are a closer marker to how cells are functioning than genes or proteins.

Therefore, measuring them may be more helpful in improving disease detection, treatment and monitoring than measuring either genes or proteins.

Image courtesy of Royston Goodacre School of Chemistry, The University of Manchester


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