Tests of ploidy and cell proliferation rate

Tests of ploidy and cell proliferation rate

The ploidy of cancer cells refers to the amount of DNA they contain. If there's a normal
amount of DNA in the cells, they are said to be diploid. If the amount is abnormal, then
the cells are described as aneuploid. Tests of ploidy may help determine prognosis, but
they rarely change treatment and are considered optional. They are not usually
recommended as part of a routine breast cancer work-up.
The S-phase fraction is the percentage of cells in a sample that are replicating (copying)
their DNA. DNA replication means that the cell is getting ready to divide into 2 new
cells. The rate of cancer cell division can also be estimated by a Ki-67 test. If the S-phase
fraction or Ki-67 labeling index is high, it means that the cancer cells are dividing more
rapidly, which indicates a more aggressive cancer.
Tests of gene patterns
Researchers have found that looking at the patterns of a number of different genes at the
same time (sometimes referred to as gene expression profiling) can help predict whether
or not an early stage breast cancer is likely to come back after initial treatment. Two such
tests, which look at different sets of genes, are now available: the Oncotype DX® and the
MammaPrint®
Oncotype DX®: The Oncotype DX test may be helpful when deciding whether additional
(adjuvant) treatment with chemotherapy (after surgery) might be useful in women with
certain early-stage breast cancers that usually have a low chance of coming back (stage I
or II estrogen receptor–positive breast cancers without lymph node involvement). Recent
data has shown it may also be helpful for patients with positive lymph nodes.
The test looks at a set of 21 genes in cells from tumor samples to determine a 'recurrence
score', which is a number between 0 and 100:
· Women with a recurrence score of 17 or below have a low risk of recurrence (cancer
coming back after treatment) if they are treated with hormone therapy. These women
would probably not benefit from chemotherapy.
· Women with a score of 18 to 30 are at intermediate risk and some might benefit from
chemotherapy.
· Women with a score of 31 or more are at high risk and are likely to benefit from
chemotherapy in addition to hormone therapy.

The test estimates risk, but it cannot tell for certain if any particular woman will have a
recurrence. It is a tool that can be used, along with other factors, to help guide women
and their doctors when deciding whether more treatment might be useful.
MammaPrint®: This test can be used to help determine how likely certain early-stage
(stage I or II) breast cancers are to recur in a distant part of the body after initial
treatment. It can be used for either ER-negative or ER-positive tumors.
The test looks at the activity of 70 different genes to determine if the cancer is low risk or
high risk.
Usefulness of these tests: While many doctors use these tests (along with other
information) to help make decisions about offering chemotherapy, others are waiting for
more research to prove they are helpful. These tests are now being looked at in large
clinical trials. In the meantime, women may want to discuss with their doctors whether or
not these tests might be useful for them.