ASCO 2015: Studies on Hormone-Positive Breast Cancer

Breast Cancer News
June 2, 2015
By: 
Erin Rowley, Writer and Content Coordinator

On Monday, at the American Society of Clinical Oncology (ASCO) meeting, in Chicago, oralinfo-icon presentations of breast cancer studies took place. Here are some of the findings related to breast cancer that is hormone receptorinfo-icon-positive, meaning it grows in the presence of the hormones estrogeninfo-icon, progesteroneinfo-icon or both:

Palbociclib

Possibly practice-changing breast cancer news was released about palbociclib (Ibrance). This medicineinfo-icon was approved by the FDAinfo-icon in February for postmenopausalinfo-icon women with estrogen receptor-positiveinfo-icon, HER2-negative metastaticinfo-icon breast cancer, in combination with letrozoleinfo-icon (Femarainfo-icon), a kind of hormonal therapyinfo-icon called an aromatase inhibitorinfo-icon. 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 tumorinfo-icon cells grow and divide.

Medicines usually aren’t approved by the FDA until after a phase III trialinfo-icon, but palbociclib was granted accelerated approval because of exciting phase II trialinfo-icon results that suggested it could double progression-free survivalinfo-icon, 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 fulvestrantinfo-icon, 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 placeboinfo-icon
  • 9.2 months in the group that received fulvestrant and palbociclib

In general, participants who took the palbociclib regimeninfo-icon had manageable side effects, but most did experience low white blood cellinfo-icon counts that could make infectioninfo-icon more likely.

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 hormoneinfo-icon-positive metastatic breast cancer that grew despite other hormonal therapies, talk with your doctor about clinicalinfo-icon trials that might look at this or other treatments.

Tamoxifeninfo-icon or Aromatase Inhibitor for DCISinfo-icon?

Ductal carcinoma in situinfo-icon, or DCIS, is a noninvasiveinfo-icon breast cancer in which abnormalinfo-icon cells are found in the lining of the breast ducts. Surgeryinfo-icon, radiation therapyinfo-icon 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 cancerinfo-icon.

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 lumpectomyinfo-icon to 5 years of either tamoxifen or the aromatase inhibitor anastrozoleinfo-icon (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.

Bone Health

Two studies presented during Monday’s oral presentations dealt with medicines that can preserve bone health and decrease chance of breast cancer recurrenceinfo-icon or death.

The first study, SWOG S0307, involved bisphosphonates, medicines that prevent natural cellinfo-icon breakdown of bones. The study gave one of three bisphosphonates: zoledronic acidinfo-icon (Zometainfo-icon) by infusioninfo-icon, clodronateinfo-icon (Bonefos) by mouth or ibandronateinfo-icon (Boniva) by mouth, to women with early-stage breast cancerinfo-icon. 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 jawinfo-icon, 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 veininfo-icon 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 denosumabinfo-icon (Xgevainfo-icon). The second study gave this medicine to postmenopausal women with early-stageinfo-icon, 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.

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Additional Related Topics 
DCIS
Targeted Therapy
Bone Health