However, the studies necessary to develop evidence of the value of these tests may be
costly and lengthy, especially for tests used for cancer screening. This deters diagnostic
companies from conducting such studies.
A few examples of diagnostic tests now in use:
- A whole-genome screen to identify those genes active in cutaneous T-cell
lymphoma,
CTCL cells that govern whether the cancer cells respond to the drug
SAHA (Vorinostat or Zolinza)
or not.
- Oncotype DX, a diagnostic test on a chip engineered to detect patterns of genetic
abnormalities within tumors. These patterns are prognostic and can help guide
treatment decisions. This test is available for both breast and colon cancer.
For more information on diagnostic tests go to:
http://cisncancer.org/research/new_treatments/molecular_diagnostics/index.html
4. Pharmacogenomic Testing:
Dihydropyrimidine dehydrogenase test. The medication 5-fluorouracil (5-FU) is
one of the most commonly used chemotherapy medications. Some people have a
genetic variation that results in a decrease in the dihydropyrimidine dehydrogenase
enzyme, which is responsible for breaking down 5-FU.
| |
|
|
 |
|
As a result of this
deficiency, some people
may develop severe or
even fatal reactions to 5-
FU. |
Image Courtesy: Erasmus MC at University Medical Center Rotterdam |
|
|
Knowing ahead of time who has this deficiency can help doctors tailor the
medication dosage to prevent these kinds of dangerous adverse reactions.
5. Using Biomarkers
A major challenge in development of cancer biomarkers will be the integration of
proteomics with genomics and metabolomics data, as well as their interpretation with
clinical data and epidemiology. It is also necessary to distinguish between the various
types of biomarkers:
| |
|
 |
Disease-related biomarkers give an indication of whether
there is a threat of disease (risk indicator or predictive
biomarkers), if a disease already exists (diagnostic biomarker),
or how such a disease may develop in an individual case
(prognostic biomarker).
The early stages of cancer development carry the maximum
potential for successful treatment interventions. However, these
stages are often asymptomatic, leading to delayed diagnosis.
Biomarkers have the potential to lead the way in early
diagnosis. Drug-related biomarkers indicate whether a drug will be
effective in a specific patient and how the patient's body will
process it. |
| Image provided by CISN archives. All rights reserved. |
|
A few examples
- Prostate specific antigen (PSA): Elevated levels may suggest the presence of
prostate cancer (see problems below).
- Cancer antigen 125 (CA-125): Elevated levels suggest recurrent ovarian cancer.
Unfortunately, both tests may result in:
False negatives - failure to detect cancer in those who have it (poor sensitivity), or
False positives - a positive test result for the presence of cancer in people who are
actually cancer-free (poor specificity).
- Measuring for the erbB2 and EGFR proteins for selecting breast, lung and colorectal
cancer patients for specific targeted therapies.
For a table with 30 protein tumor
markers and where they are used, go to:
http://cisncancer.org/research/new_treatments/tumor_markers/promise_003.html
| |
| |
|
Image provided by CISN archives. All rights reserved.
|
| |
Human DNA may be 99.9% similar across the population but just like Zebras, that
remaining .1% allows us to each display our individual "stripe".
