A very small, very early study found that the experimental targeted therapy dovitinib didn't benefit women diagnosed with metastatic, HER2-negative breast cancer.
Metastatic breast cancer is cancer that has spread to a part of the body away from the breast, such as the bones or the liver. The research was published in the Journal of Clinical Oncology and presented at the 2011 annual meeting of the American Society of Clinical Oncology (ASCO).
About one out of every four breast cancers is HER2-positive, so three out of four are HER2-negative. HER2-positive breast cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. HER2-positive cancers tend to be more aggressive and harder to treat than breast cancers that are HER2-negative. Still, targeted therapies such as Herceptin (chemical name: trastuzumab) and Tykerb (chemical name: lapatinib), which can help treat HER2-positive breast cancers, don't work on HER2-negative breast cancers. Researchers are looking for targeted therapies for HER2-negative breast cancer, especially for metastatic HER2-negative breast cancer.
Like the HER2 protein, FGFR1 (fibroblast growth factor receptor 1) is a protein that sits on the surface of cells. On breast and other cancer cells, the FGFR1 protein receives signals that can encourage the cancer cells to grow and spread. Some breast cancers make too much of the FGFR1 protein and are called FGFR1-positive. It's also said that these cancer cells overexpress FGFR1 or have FGFR1 amplification. Right now, doctors don't routinely test to see if a breast cancer is FGFR1-positive or FGFR1-negative. Still, researchers have found that about 8% to 10% of breast cancers are FGFR1-positive. Breast cancers that are FGFR1-positive tend to be more resistant to treatments, including hormonal therapy if the cancer also is hormone-receptor-positive.
The experimental targeted therapy dovitinib was created to attach to the FGFR1 protein and block it from receiving growth signals. Researchers also are doing very early studies on using dovitinib to treat skin cancer (melanoma), kidney cancer, as well as breast cancer, whether or not the cancer is FGFR1-positive. Dovitinib is a pill taken by mouth.
In this study:
- 61% of 68 women were diagnosed with HER2-negative, metastatic breast cancer that had spread to three or more parts of the body away from the breast.
- 78% of the women had cancer that had spread to the liver.
- All the women already had received one or more metastatic breast cancer treatments.
- 21 women had cancers that were FGFR1-positive and hormone-receptor-positive.
All the women were treated with dovitinib. Response to treatment was recorded 4 to 6 weeks after the women started taking dovitinib and again 20 or more weeks later. Treatment response was measured in terms of clinical benefit: either the cancer showed signs of being weakened by the treatment (partial response) or the cancer didn't grow while the women took the treatment (stable disease).
Dovitinib seemed to offer the most benefits to the 21 women diagnosed with FGFR1-positive AND hormone-receptor-positive breast cancer:
- 55% of the women had stable disease and 15% (3 women) had partial response 4 to 6 weeks after treatment started.
None of the other women had a partial response to treatment after 4 to 6 weeks, though many had stable disease.
Only a few women showed any clinical benefit from dovitinib 24 or more weeks after they started taking dovitinib. Women with FGFR1-positive and hormone-receptor-positive cancer showed the greatest clinical benefit; still, it was only 15% of those women.
Despite the less-than-promising results, the researchers think that dovitinib may still be a good treatment for some women diagnosed with advanced-stage breast cancer. It's possible that women diagnosed with metastatic breast cancer might get more benefits from dovitinib if it's used earlier in the treatment plan or if the cancer hasn't spread as much. Much more research is needed before doctors can understand which group of women may benefit from dovitinib and when and how it might be best used to treat metastatic breast cancer.
If you're being treated for metastatic breast cancer, you and your doctor may be considering a number of options, especially if the cancer is HER2-negative and/or has stopped responding to standard treatments. Despite the weak results seen in this study, treatment with an experimental regimen that includes a targeted therapy like dovitinib may be an option if you're willing to participate in a clinical trial. Ask your doctor if there are any clinical trials that might be a good fit for you and your unique situation. Visit the Breastcancer.org Clinical Trials pages for more information.