The San Antonio Breast Cancer Symposium provides an excellent opportunity to learn about the latest findings in breast cancer research–directly from the researchers. I had attended last year for the first time, and was excited to be able to go to the event again this year.
There were some very intriguing presentations this year about possible new therapeutic approaches that are either now in clinical trials or will be entering them soon. In that vein, I’ll describe two areas of longer-term research that received a significant amount of coverage. Also very noteworthy were two sets of findings that could lead to less toxic treatments for some patients, and one study that could eventually lead to a new prevention strategy for women who are at high risk for breast cancer.
These are my top five takeaways from SABCS 2013.
1) A new targeted therapy for BRCA-mutated and triple negative breast cancers is being studied in clinical trials now.
A new category of drugs, known as PARP inhibitors, is being tested in clinical trials. PARP is a protein that is involved in repairing damaged DNA. It can enable tumor cells to survive and grow, and it seems to play a greater role in cancers that have BRCA mutations. It is believed that PARP inhibitors could be effective as stand-alone treatment or could make standard chemotherapy drugs more effective.
Testing of one PARP inhibitor, with the name BMN 673, has recently begun in a Phase III clinical trial. Dennis Slamon, Ph.D., M.D., who is well-known for his role in the development of trastuzumab (Herceptin), was also involved in the work on BMN 673. Dr. Slamon spoke to a meeting of advocates in San Antonio and explained that PARP inhibitors may play a role in all breast cancer subgroups, including triple negative. He also said that breast cancer cell lines have been found to be highly sensitive to BMN 673.
We also heard about another PARP inhibitor in a report about the ongoing I-SPY2 clinical trial, an innovative clinical trial that is testing a number of different drugs. In the I-SPY2 trial, a PARP inhibitor called veliparib was tested in combination with the chemotherapy drug, carboplatin and standard chemotherapy, compared to the standard chemotherapy alone. In this trial, drugs are given prior to surgery and their effectiveness is evaluated in the breast and lymph node tissue subsequently removed in surgery. The veliparib/carboplatin combination was found to be particularly effective in triple negative breast cancer. The treatment will now move on to further testing with a larger group of patients in a Phase III clinical trial. Also, since this particular study looked at veliparib and carboplatin together, the extent to which each of the drugs contributed to the improved response is not clear, and further study will be needed to gain greater understanding of the benefits of each in breast cancer treatment.
2) Helping the body’s own immune system to attack cancer cells is an evolving area of research in breast cancer.
Boosting the immune system to help fight cancer is perhaps one of the hottest areas of cancer research right now. Especially noteworthy at this Symposium were findings from a study relevant to HER2-positive breast cancer. This study showed that levels of a particular type of immune system cell, “tumor infiltrating lymphocytes” or “TILs”, within a patient’s tumor are a good indicator of the likelihood that therapy with Herceptin will be effective for that patient. Levels of TILs were also found to be a good biomarker for the success of chemotherapy.
Research is ongoing to find ways to bolster the work of these important immune system components. One approach is by using a type of drug therapy that aids their functioning. An example is the drug ipilumumab (Yervoy), which is now is use for melanoma. It was mentioned that similar drugs are being studied in breast cancer treatment. Another approach being studied is a type of gene therapy in which other cells are genetically engineered to behave like TILs and are used to supplement the activity of naturally occurring TILs.
3) Less toxic chemotherapy, together with Herceptin, may work just as well as a more toxic chemo combination in HER2-positive breast cancer.
The APT clinical trial, described as a rare “practice-changing” smaller trial by one of the doctors in the daily session for advocates, reported out results that showed patients receiving Herceptin and paclitaxel (Taxol) did just as well as would have been expected if they had received Herceptin and a more toxic chemotherapy regimen containing an anthracycline.
The APT trial involved lower-risk HER2-positive patients with tumors less than 1 centimeter in size. But interestingly, findings that were reported from another trial, the Phase III BETH trial, showed similarly equivalent benefits for a less toxic chemotherapy regimen in higher risk HER2-positive patients. The BETH trial also showed there was no benefit from the addition of the angiogenis inhibitor, bevacizumab (Avastin), to the treatment regimen for these patients.
4) Radiation may not be necessary for some breast cancer patients that are over 65.
Early results of another interesting study, the PRIME II trial, showed that some women over 65 who receive anti-hormone therapy and breast-conserving surgery may do just as well without the addition of radiation therapy as with it. These findings could be pretty significant since about half of all breast cancer patients are women over 65. That said, the study has only had a few years to follow patients so far, and we will need to watch to see if longer term follow up confirms this finding. The findings were for women with hormone receptor-positive, node-negative breast cancer.
5) The anti-estrogen therapy, Arimidex, could become a new option as a prevention strategy for postmenopausal women at high risk for breast cancer.
Another clinical trial reporting its initial results showed that the anti-estrogen therapy, anastrazole (Arimidex) could become a viable prevention strategy for women at high risk for the disease. These results were also simultaneously published in the journal The Lancet. The incidence of invasive breast cancer declined by 53% in about 1,900 women receiving Arimidex, compared with another 1,900 women who received a placebo. The women have been followed for 5 years. Again, longer term follow up will be essential to see if these results hold up. There are some side effects with this therapy, but they seem to be less than for tamoxifen and raloxifene, two other anti-estrogen therapies that are sometimes used to prevent breast cancer.
For More Information
If you’re interested in reading more about findings from the Symposium, check out these resources:
- A series of articles by Dr. Susan Love on the Dr. Susan Love Research Foundation website;
- blog posts by Dr. Robert Miller and Dr. Julie Gralow on the #BCSM website; and
- the press releases issued by SABCS, which announce major research findings presented at the Symposium.
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