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.
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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.