ASCO 2015: Studies on Hormone-Positive Breast Cancer
On Monday, at the American Society of Clinical Oncology (ASCO) meeting, in Chicago, oral presentations of breast cancer studies took place. Here are some of the findings related to breast cancer that is hormone receptor-positive, meaning it grows in the presence of the hormones estrogen, progesterone or both:
Possibly practice-changing breast cancer news was released about palbociclib (Ibrance). This medicine was approved by the FDA in February for postmenopausal women with estrogen receptor-positive, HER2-negative metastatic breast cancer, in combination with letrozole (Femara), a kind of hormonal therapy called an aromatase inhibitor. It was the first cyclin-dependent kinase (CDK) 4/6 inhibitor to be approved by the FDA. This type of medicine targets two specific kinases, or enzymes, that help tumor cells grow and divide.
Medicines usually aren’t approved by the FDA until after a phase III trial, but palbociclib was granted accelerated approval because of exciting phase II trial results that suggested it could double progression-free survival, the time between starting treatment and the disease growing.
Lead researcher Nicholas C. Turner, MD, of the Institute of Cancer Research in London, presented the results of the phase III PALOMA3 trial, which were also published online in the New England Journal of Medicine. He reported that palbociclib when given with fulvestrant, a hormonal therapy used in metastatic disease, more than double PFS for women with hormone receptor-positive, HER2-negative metastatic breast cancer that had progressed on prior hormonal therapy. Unlike the phase II study, both pre- and postmenopausal women were included in this analysis. The PFS was:
- 3.8 months in the group that received fulvestrant and a placebo
- 9.2 months in the group that received fulvestrant and palbociclib
Information about overall survival (OS), the time from breast cancer treatment until death from any cause, is not yet available.
The fulvestrant-palbociclib treatment combination is not yet FDA approved, but this study shows promise. If you have hormone-positive metastatic breast cancer that grew despite other hormonal therapies, talk with your doctor about clinical trials that might look at this or other treatments.
Ductal carcinoma in situ, or DCIS, is a noninvasive breast cancer in which abnormal cells are found in the lining of the breast ducts. Surgery, radiation therapy and the hormonal therapy tamoxifen is a standard treatment regimen for DCIS, which has a goal of keeping the DCIS from returning and becoming invasive breast cancer.
But researchers with the NSABP B-35 trial wanted to know if an aromatase inhibitor would be better than tamoxifen at keeping women with DCIS breast cancer-free. They randomly assigned postmenopausal women with hormone receptor-positive DCIS who had had a lumpectomy to 5 years of either tamoxifen or the aromatase inhibitor anastrozole (Arimidex).
Lead researcher Richard G. Margolese, MD, of Jewish General Hospital, in Montreal, Canada, reported that after a mean follow-up time of 8.6 years, women under 60 years of age who took anastrozole were significantly more likely to be free of invasive disease than women in that age group who took tamoxifen. In older women, the two treatments worked just as well. This finding could be of interest to doctors who treat those with DCIS.
Two studies presented during Monday’s oral presentations dealt with medicines that can preserve bone health and decrease chance of breast cancer recurrence or death.
The first study, SWOG S0307, involved bisphosphonates, medicines that prevent natural cell breakdown of bones. The study gave one of three bisphosphonates: zoledronic acid (Zometa) by infusion, clodronate (Bonefos) by mouth or ibandronate (Boniva) by mouth, to women with early-stage breast cancer. Ibandronate, a pill, is not FDA approved for use in the United States.
The researchers wanted to learn which medicine would lead to longer disease-free survival (DFS), the length of time after breast cancer treatment that a person survives with no sign of the disease. They were also interested in learning if one medicine would lead to longer overall survival.
No significant differences in DFS or OS were found between the three bisphosphonates. Five-year DFS was about 88 percent and OS was 93 percent. The researchers found that fewer participants on zoledronic acid stopped taking their medicine because of side effects. Osteonecrosis of the jaw, painful exposed bone in the jaw, was seen more often with zoledronic acid than with the other bisphosphonates, but was still seen in fewer than 2 percent of participants who took zoledronic acid.
About three-quarters of participants told the researchers that if bisphosphonates given by vein and those taken by mouth worked equally well, they would prefer to use the bisphosphonates that they could take by mouth. But currently no bisphosphonates taken by mouth are FDA approved for use in breast cancer.
Given participant preference, efforts should be made to make oral bisphosphonates available to people with breast cancer, said lead researcher Julie Gralow, MD, of the Seattle Cancer Care Alliance and the University of Washington School of Medicine.
Another medicine that can prevent or treat bone problems in people with breast cancer is denosumab (Xgeva). The second study gave this medicine to postmenopausal women with early-stage, hormone receptor-positive breast cancer receiving treatment with aromatase inhibitors.
Lead researcher Michael Gnant, MD, of the Medical University of Vienna, in Vienna, Austria, reported that women who took denosumab had fewer bone fractures than women on a placebo, and if they did experience a fracture, the time between treatment and that fracture was about twice as long as it was for women on a placebo. These results were similar whether the woman started the trial with normal or low bone strength. People who took denosumab had few side effects; rates were similar between the denosumab and placebo groups.
During the discussion, the doctors noted that these medicines are not normally given to women with normal bone strength. Some said the findings suggest women who have had breast cancer treatment are at greater risk for fracture, even if their bones look healthy based on scans. They recommended further study.
Check back for information about presentations specific to HER2-positive and triple-negative disease and don’t forget to join us for our annual ASCO webinar on Thursday, June 4.