Genetic
Test Helps Predict Risk of Recurrence in Node-Negative Breast
Cancer
According to results recently presented at the 2003 San Antonio
Breast Cancer Symposium, a novel test involving the expression
of 21 genes could help predict the risk of a cancer recurrence,
and ultimately aid in treatment decisions for patients with
node-negative, estrogen-receptor positive breast cancer. This
is the first diagnostic test of its kind that would be commercially
available for patients with cancer.
Breast cancer that has not spread to lymph nodes under the
arm (axillary) is referred to as node-negative. Patients with
node-negative breast cancer may be offered chemotherapy following
the surgical removal of their cancer in order to reduce the
risk of a cancer recurrence. However, a large portion of these
patients are not at a considerable risk for a cancer recurrence
and do not benefit from treatment with chemotherapy. Patients
not at risk for a recurrence who undergo chemotherapy are
subject to unnecessary side effects of chemotherapy, time
involved with chemotherapy treatments, and accrued medical
costs. At present, physicians try to categorize patients with
node-negative breast cancer at a higher or lower risk for
a recurrence, using a list of patient and disease characteristics
to help guide in treatment decisions. Age of a patient, nodal
status, hormone-receptor status, HER2 status, size of the
cancer, the aggressiveness of the cancer, and the extent to
which the cancer has invaded tissues are some of the factors
considered when categorizing a patient to a higher or lower
risk category. However, researchers have been evaluating ways
to improve upon the present classification system, as some
patients considered to be low risk will develop a cancer recurrence
following chemotherapy, and some patients considered to be
high risk will remain cancer free after no chemotherapy.
The integration of genetics into the clinical setting has
been an area of much focus. One of these areas has been the
evaluation of several genes and the association of combinations
of several genes as indicators of patient outcomes. It is
believed that one main reason behind the differences in response
rates and survival rates among patients with the same type
and extent of cancer who are treated with the same therapeutic
regimen is the differences in gene expression of individual
cancers. Therefore, identifying and understanding which genes
are associated with particular outcomes, or sensitivity to
specific therapies, will help individual treatment options,
sparing patients from treatment that does not provide benefit,
and optimizing overall treatment choices.
Researchers associated with the National Surgical Adjuvant
Breast and Bowel Project (NSABP) conducted a clinical study
evaluating several genes and the associations of the expression
of these genes and patient outcomes in breast cancer. A database
of over 200 selected genes was initially used, and tested
in a validation study involving over 660 patients. The validation
study included patients with node-negative, estrogen-receptor
(ER)- positive breast cancer who had been treated with the
anti-estrogen agent tamoxifen (Nolvadex ®). A genetic component
of the cancer, called RNA, was tested from biopsy specimens
that had been stored. Patients had been followed for over
10 years. The results of this study led to the identification
of 16 genes that are strongly associated with recurrence potential
of cancer. The patient's biopsy specimens were tested and
compared to the diagnostic gene test, which includes the 16
genes associated with recurrence and 5 genes used as ?reference?
genes to aid in laboratory processes. Depending upon specific
combinations of genes expressed by the cancer, patients fell
into categories of low, intermediate and high-risk for the
development of a cancer recurrence. Patients at low risk had
approximately a 7% rate of a recurrence at 10 years, patients
at intermediate risk had approximately a 14% rate of a recurrence
at 10 years, and patients at high risk had approximately a
31% rate of a recurrence at 10 years. Overall, in this study,
over half (51%) of patients were low risk, 22% were intermediate
risk, and 27% were high risk. The gene assay test was more
accurate in predicting recurrence rates than either age of
the patient or size of cancer.
The researchers concluded that this 21-gene diagnostic test
appears to provide great accuracy in predicting the risk of
a recurrence in patients with node-negative, ER-positive breast
cancer who have been treated with tamoxifen. Results from
this test will most likely become an important tool in determining
optimal treatment regimens for this group of patients, ultimately
sparing patients from unnecessary therapy and guiding patients
at high risk to more aggressive therapy. This test will is
scheduled to become commercially available in the beginning
of 2004. Studies evaluating gene profiles in various cancers
are underway, and are expected to become part of routine diagnostic
measures. Patients with node-negative, ER-positive breast
cancer may wish to speak with their physician about the future
availability of this test.
Reference: Paik S, Shak S, Tang G, et al. Multi-gene RT-PCR
assay for predicting recurrence in node negative breast cancer
patients - NSABP studies B-20 and B-14. Presented at: 26th
Annual San Antonio Breast Cancer Symposium. December 3-6,
2003; San Antonio, TX. Abstract #16.
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