Breaking down breast cancer
Breast cancer sufferers are avoiding unnecessary chemotherapy through transcriptional profiling that examines the genetic make-up of their cancer.
Not too long ago, chemotherapy was almost always part of the standard treatment for breast cancer. Yet with advances in gene mapping, this is no longer the case. The fact is that numerous cases of breast cancer do not necessitate or benefit from chemotherapy. Through mapping the genes of breast cancer cells, doctors can determine whether or not this gruelling course of treatment is actually needed.
What is transcriptional profiling?
‘Transcriptional profiling is a measure of activity of several or thousands of genes at once,’ says Dr Richard Khanyile, a medical oncologist at Mediclinic Muelmed. This allows doctors to determine whether a patient with early hormone receptor positive breast cancer will benefit from chemotherapy or not, after lumpectomy or mastectomy,’ he explains.
HER2 (human epidermal growth factor receptor 2) is found on the surface of the breast and is a protein that promotes the growth of cancer cells. If the cancer is HER2-negative or estrogen- and progesterone-receptor positive, hormone therapy, which limits growth of these hormones or blocks the cancer cell’s exposure to them – may be more effective.
At the moment, this profiling is used only for breast cancer. ‘Most of the gene expression profiling tests are used in other cancers but only at experimental level,’ Dr Khanyile explains.
Why avoid chemotherapy?
Although chemotherapy is generally physically and emotionally challenging, it’s also often a necessary and highly effective form of cancer treatment. However, when it’s not actually needed, it’s definitely best avoided so that patients can skip the difficult side effects. ‘Transcriptional profiling helps oncologists decide if chemotherapy would be the right form of cancer treatment for the type of cancer a patient has,’ says Dr Khanyile.
‘There are several types of gene expression profiling combinations that are used in breast cancer. MammaPrint and Oncotype DX are most commonly used,’ Dr Khanyile says. ‘These were initially used as a form of prognosis but now are also used to predict whether or not to use chemotherapy in early breast cancer.’
With MammaPrint, a sample of the tumour is sent to a lab in the Netherlands, which analyses its DNA to see how active its genes are. ‘Instead of looking at external features of the cancer, we’re looking at the DNA of the cancer itself to predict its behaviour better early on,’ explains Dr Etienne Myburgh, an oncology surgeon at Mediclinic Panorama. Results either reveal a high-risk cancer that has a long-run risk of spreading and would probably benefit most from chemotherapy, or it could be a low-risk cancer that has a substantially lower risk of spreading.
This genomic test analyses the activity of 21 genes that can influence how likely a cancer is to grow and respond to treatment. This not only predicts whether or not chemotherapy and radiation will be beneficial, but also how likely the breast cancer is to return.
The results of a recent clinical study sponsored by the National Cancer Institute and conducted amongst 10 000 women who had been diagnosed with hormone-receptor positive, HER2-negative breast cancer that had not spread to the lymph nodes, reinforce the value of the Oncotype DX genomic test. ‘16% of women had a test result indicating a very low risk for recurrence,’ reports the National Institutes of Health. ‘These women did not receive chemotherapy, but did receive standard hormone therapy. Researchers followed up five years later and found that the risk for any breast cancer recurrence for these women was less than 2%, and the risk for a recurrence at a distant site was less than 1%. The overall survival rate was 98%.’