|
Diagnostic Testing Before TDT
Historically, physicians have relied on the results of histopathology
in evaluating lymph nodes to detect the spread of colon cancer,
or CEA (carcinoembryonic antigen) blood tests to determine colon
cancer recurrence. Both testing methods can be inaccurate, reflecting
errors in sampling and sensitivity. Studies have suggested that
30% of cancer-bearing lymph nodes are under-staged as cancer-free
by histopathology. Similarly, current CEA-based blood tests detect <60%
of recurrent cancers.
TDT's Breakthrough Discovery
TDT has discovered a unique cell surface receptor that is found
on colorectal cancer cells and not on any normal cell outside
the
intestine. This receptor is called guanylyl
cyclase C (GC-C). It provides a superior mechanism for
detecting the presence of colorectal cancer cells because it
relies on ultrasensitive
messenger RNA-based amplification technology rather than other
less sensitive and variable detection systems, such as the human
eye.
Assessing Tumor Stage and Treatment Options
There are various methods of staging used to describe how far the
colon cancer has spread in a patient. Generally, these staging systems
are based on the depth of penetration of the cancer cells into the
wall of the colon, and whether or not it has spread to nearby lymph
nodes.
If the cancer is early stage (shallow penetration into the
intestinal wall and no evidence of spread to surrounding lymph nodes),
surgery alone may be sufficient. If the cancer cells have spread
to the lymph nodes, then the risk of recurrence is substantial and
the physician may recommend the use of chemotherapy (frequently,
5-flurouracil and leucovorin).
In order to provide the patient with the best survival outcome,
it is critical that the information available to the physician on
the spread (stage) of the disease be accurate. The technology
developed by TDT gives the physician a higher degree of sensitivity
and specificity than evaluation of tissues by histopathology. Indeed,
the TDT technology can detect 1 cancer cell in 10,000,000 cells
and approaches 100% specificity, where histopathology can fail
to detect microscopic cancer cells when there are less than 1 in
200 normal cells.
Monitoring for Cancer Recurrence
Another critical component of colon cancer care is post surgical
monitoring for cancer recurrence. After surgery and treatment, physicians
typically monitor patients for evidence of recurrence for up to
5 years.
Traditionally physicians have relied on a blood test, scheduled
in regular intervals, to measure levels of a protein called carcinoembryonic
antigen (“CEA”). However, CEA is limited as
a marker for colon cancer, detecting less than 60% of recurrent
tumors.
It also has a high false positive rate and is influenced by some
nonmalignant conditions such as cirrhosis, ulcerative
colitis and
even smoking. In addition, elevated CEA is associated with a number
of tumors other than colorectal such as breast, pancreas and bladder.
TDT has developed a blood test using GC-C as a marker,
which represents a significant improvement over CEA determinations
for detecting
circulating metastatic colorectal cancer cells. The test can detect
1 cancer cell in 10,000,000 normal blood cells (1 cancer cell
in
1-10 mL of blood).
|
