Women with aggressive breast cancer who receive combination targeted therapy with chemotherapy prior to surgery have a slightly improved chance of staying cancer-free, researchers say.
However, the improvement was not statistically significant and the jury is still out on combination treatment, said lead researcher Dr. Martine Piccart-Gebhart, chair of the Breast International Group, in Brussels.
"I don't think that tomorrow we should switch to a new standard of care," she said.
Piccart-Gebhart presented her findings Wednesday at the 2013 San Antonio Breast Cancer Symposium, alongside other research that investigated ways to improve treatment for women with HER2-positive breast cancer. This aggressive form of cancer is linked to a genetic irregularity.
Other researchers reported the following:
The targeted drug trastuzumab (Herceptin) worked better in HER2-positive breast cancer tumors containing high levels of immune cells.A combination of the chemotherapy drugs docetaxel and carboplatin with Herceptin appeared to be the best postsurgery treatment option.
Overall, the studies were good news for women with HER2-positive breast cancer, which used to be one of the most fatal forms of the disease. Researchers reported long-term survival rates higher than 90 percent for women treated using the targeted therapy drugs.
"That tells you these treatments are very, very effective," Piccart-Gebhart said.
Piccart-Gebhart's combo targeted therapy trial is evaluating whether the HER2-targeted drugs Herceptin and lapatinib (Tykerb) work better when combined on top of standard chemotherapy.
The trial involved 455 patients with HER2-positive breast cancer with tumors larger than 2 centimeters.
The women were given chemotherapy prior to surgery along with either Herceptin, Tykerb, or a combination of the two targeted drugs. They also were treated after surgery with whichever targeted therapy they had been receiving.
Piccart-Gebhart reported that 84 percent of the patients who received the combination targeted therapy between 2008 and 2010 have remained cancer-free, compared with 76 percent who only received Herceptin.
"It's too early today to say this dual treatment saves more lives. We can't say that on the basis of this trial," she noted.
The drawbacks of this combination therapy are cost and side effects, Piccart-Gebhart said. Targeted therapies cost tens of thousands of dollars, and combining the two drugs increases toxic side effects such as diarrhea and rash.
"There is a price to pay in terms of side effects," she said. "There will be a price to pay in terms of drug costs."
This study was supported by funds from GlaxoSmithKline. Piccart-Gebhart has received honoraria from Roche, and her institution has received research funding from GlaxoSmithKline.
The second study involved 156 patients who received chemotherapy and Herceptin before surgery. However, this study focused on the levels of immune cells called lymphocytes that had infiltrated the breast tumors.
For every 10 percent increase in the levels of tumor-infiltrating lymphocytes, there was a 16 percent increase in the number of patients whose breast tumors were eradicated, said lead researcher Dr. Sherene Loi.
Loi is a medical oncologist and head of the translational breast cancer genomics lab at the Peter MacCallum Cancer Center in Melbourne, Australia.
She said Herceptin might serve to activate the immune cells. However, her team found that not all women have high levels of these immune cells in their tumors.
"Previously, breast cancer has not thought to be suitable for immunotherapy approaches," Loi said. "Our results provide evidence that this could be a new strategy for treatment in breast cancer."
The third study compared the effectiveness of a combination chemotherapy using the drugs docetaxel and carboplatin against traditional chemotherapy with medications called anthracyclines.
Anthracyclines are effective in treating HER2-positive breast cancer, but have very toxic side effects that can lead to congestive heart failure and leukemia.
Doctors found that 92 percent of 3,231 women treated with the new combination chemo survived more than three years with no recurrence of their cancer.
These results make the new combination a viable alternative to anthracycline-based chemotherapy, said lead researcher Dr. Dennis Slamon, director of clinical/translational research at the Jonsson Comprehensive Cancer Center at the University of California, Los Angeles.
"It is going to be difficult to develop treatment regimens that have even better response rates than that," said Slamon, who is also chief of hematology/oncology with UCLA's department of medicine
This study was supported by funds from Roche/Genentech. Slamon has served as an adviser to both companies, including during the time period when the study was conducted.
Because the studies were presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
