PARP Inhibitors: Possible Good News
At last month's San Antonio Breast Cancer meetings, one piece of potentially very good news was a small reported study on the use of a PARP inhibitor, BSI-201 ( don't you love these catchy research names?), in treatment for women with advanced breast cancer. The caution is that this was a very small study, only 123 women, but they had all been previously treated with a range of chemotherapies and had progressing breast cancer. Additionally, there were all women with triple negative breast cancers, so we don't yet have information about the response in other varieties of the disease. All were given Gemzar and carboplatin, and half were also given BSI-201. Of the women who received the extra drug, 48% had some kind of response vs. only 16% of the group who received only the two more standard medications.
PARP inhibitors are still being tested in clinical trials and are not yet, as they say, ready for prime time. Sadly, it is worth the reminder that other things have looked promising in early data and then turned out to be less widely valuable. However, the excitement about this possible treatment is great, and, if you have Stage IV breast cancer, it might be worth talking with your doctor about a clinical trial involving this drug.
Here is a report from breastcancer.org:
SABCS: PARP Inhibitor Data Called 'Spectacular'
The very small study reviewed here found that BSI-201, an experimental targeted therapy medicine, makes chemotherapy work better against aggressive forms of breast cancer. These results confirm findings from earlier studies. These results were reported at the 2009 San Antonio Breast Cancer Symposium.
DNA carries genetic information in both healthy and cancer cells. Chemotherapy medicines work against cancer by damaging the DNA or blocking DNA reproduction. But all cells can fix DNA damage caused by chemotherapy medicines. So sometimes cancer cells may not respond or stop responding to a chemotherapy medicine. When cancer stops responding to a treatment, it's called "treatment resistance."
BSI-201 is a PARP inhibitor. The PARP (poly ADP-ribose polymerase) enzyme fixes DNA damage in cells, including DNA damage caused by chemotherapy medicines. Scientists developed PARP inhibitors based on the idea that a medicine that interferes with or inhibits the PARP enzyme might make it harder for cancer cells to fix damaged DNA, which would make it harder for cancer to become resistant to chemotherapy.
In the study reviewed here, 123 women diagnosed with advanced-stage, triple-negative (HER2-negative, estrogen-receptor-negative, progesterone-receptor-negative) breast cancer were treated with a combination of two standard chemotherapy medicines: gemcitabine (brand name: Gemzar) and carboplatin (brand name: Paraplatin). Half of the women also received BSI-201. All of the women had received a variety of other cancer treatments before this study.
The women who got the two chemotherapy medicines plus BSI-201: were more likely to respond to treatment; 48% of the women who got BSI-201 had some response
to treatment, compared to only 16% of women who didn't get BSI-201 lived longer without the cancer getting worse; women who got BSI-201 lived for almost 7 months
without the cancer getting worse, compared to about 3 months for women who didn't get BSI-201 lived longer overall; women who got BSI-201 lived for about 12 months compared to about 8 months for women who didn't get BSI-201
Women who got BSI-201 plus chemotherapy had the same types and severity of side effects as the women who got only chemotherapy.
While this study is promising, BSI-201 is considered an experimental treatment. More research is needed before doctors completely understand how and when to use PARP inhibitors to treat breast cancer.
If you're being treated for advanced-stage breast cancer, you and your doctor may be considering a number of treatment options, especially if the cancer has stopped responding to standard treatments. If you're willing to participate in a clinical trial, you may have even more options available, possibly including a PARP inhibitor. Talk to your doctor about clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.