Sorting Through the different types of Breast Cancer

Sorting Through the Different Types of Breast Cancer

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June 8, 2009 by drktruddy

Years ago doctors grouped women with breast cancer into four “stages” depending on three measures: the size of the tumor (T), the number of lymph nodes involved (N) and whether there was any evidence of metastatic disease (M). This was referred to as the TNM Staging System – and it was used to predict prognosis and tailor treatment for the individual patient. It was crude, at best; but it was all there was for many years.
Also during the last century, three other “markers” were discovered that became useful for determining treatment and gauging prognosis. They were: estrogen receptor (ER), progesterone receptor (PR) and Her2-neu. Tamoxifen, and then aromatase inhibitors (e.g., Arimidex), were used to “target” those patients whose tumors expressed ER and/or PR, and then Herceptin was created to treat those women whose tumors expressed Her2-neu.
Although TNM staging remains entrenched for grouping women with breast cancer, much-needed modifications are underway. Breast cancers have now been reclassified into four types, based on the receptors they do, or do not, express:
Luminal A – ER or PR positive, low grade (best prognosis)
Luminal B – ER or PR positive, higher grade (not great prognosis, but not terrible either)
Her 2 - expresses this receptor, associated with more aggressive disease and worse prognosis
Basal - does not express any of the receptors: poor prognosis (although responds well to chemotherapy)
The New Millennium has arrived and with it an entirely new way of understanding the “language” of cancer: this is done by gene array analysis. In short, this is the newest and best way to understand how cancers behave AT THE LEVEL OF THE GENES THEY EXPRESS. Wonderful, except it is very expensive and time-consuming. Good news: researchers have identified an “old-fashioned” laboratory way to distinguish Luminal A from Luminal B tumors (this can be tricky) based on a test called, Ki67. This additional test is a marker for proliferative potential of the tumor, a way of gauging how aggressively it may grow.
Dr. Chang has published a paper in the Journal of the National Cancer Institute that shows that Ki67 levels are a good way to tell a typical Luminal A from a typical Luminal B breast cancer – in addition to the parameters given above: 14% is the cutoff.
If the Ki67 is below 14%, the tumor can be considered Luminal A; if the Ki67 is over 14% then it can be considered a Luminal B.
It is not certain what difference this will make for treatment at the moment. But women, and the physicians who care for them, will have another piece of cost-effective and readily available information that, in the near future, might help design an even better fit between the patient and her treatment.

Chang, JNCI 2009. 101: 736-750