Chromosome Number, Her2 Status, and Oncogenes

Do the cancer cells have a normal number of chromosomes?

Doctors also use ploidy, a measurement of the number of chromosomes present in cancer cells, to determine how fast a tumor may be growing:

• Diploid cancer cells have a normal number of chromosomes.
• Aneuploid cells have more chromosomes than normal, because they are growing faster than normal cells and need extra genetic material to pass on to the new cells they make.
• Diploid cancers have more favorable outcomes than aneuploid cancers. But ploidy is just one factor in the grand scheme of cancer personality. This feature on its own does not have a major impact on your outcome.

Is the cancer the result of oncogene overexpression?

Your doctors will also try to measure proteins "secreted" (or produced) by the breast cancer cells. They are looking for something called oncogene overexpression or amplification. Oncogenes are bits of genetic information inside the body's cells that usually work to protect us from cancer, by keeping cell growth in check.

Oncogene overexpression happens when an oncogene (such as the one called HER2/neu) malfunctions and "overexpresses" itself (like screaming instead of talking) by making excess normal or abnormal proteins and receptors. This can lead to cancer. Cancers that result from overexpressed oncogenes such as HER2/neu tend to be more nasty or belligerent and are more likely to recur than other cancers. They also may respond to different types of treatment than other breast cancers.

We know about several oncogene abnormalities that are involved in breast cancer, including HER2/neu, EGFR, and p53 (which can be inherited).

Knowing that a cancer is derived from oncogene overexpression may help your doctor choose a more effective form of treatment for you. For example, overexpression of the HER2/neu protein or receptor may:

• predict a good response to Herceptin (chemical name: trastuzumab), a specialized medicine used to combat the HER2/neu protein
• predict a poor response to CMF chemotherapy and tamoxifen
• indicate a need for a higher dose of CAF chemotherapy to get the best response.

If you're not tested for oncogene overexpression, don't be surprised. These tests still aren't routine, although much early research suggests that the information they provide will be increasingly valuable in the future. However, the test for HER2/neu is an important part of your big picture and you should ask for it.

More about:

• Chemotherapy regimens
• Tamoxifen