What's Hot at the 2011 San Antonio Breast Cancer Symposium

Nick Mulcahy

November 28, 2011

November 28, 2011 — Results from a number of high-profile clinical trials of bisphosphonates in breast cancer will be among the headlining news from the 34th Annual San Antonio Breast Cancer Symposium (SABCS), being held December 6 to 10 in Texas.

Vying for attention at the meeting will be the Institute of Medicine's report on environmental factors and breast cancer as well as new results from major clinical trials in advanced breast cancer.

Additionally, there will be a report on the first-ever genomic profiling study of ductal carcinoma in situ (DCIS), an analysis of the overdiagnosis of breast cancer from mammography screening, and the results from an international study of axillary lymph node dissection in patients with clinically node-negative breast cancer and micrometastases in the sentinel node.

Overall, the 2011 meeting looks especially exciting, said Peter Ravdin, MD, PhD, a co-director of the symposium. "We have a lot of outstanding presentations this year, even more so than usual," he told Medscape Medical News. Dr. Ravdin is director of the Comprehensive Breast Health Clinic at the Cancer Therapy & Research Center, University of Texas Health Science Center at San Antonio.

There will be presentations of new data from 4 separate clinical trials of bisphosphonates in patients with breast cancer.

The presentations include new, long-term data from the Austrian Breast and Colorectal Cancer Study Group (ABCSG) 12 trial, which examines the effect of zoledronic acid (Zometa, Novartis) on outcomes in premenopausal women with estrogen-responsive early breast cancer. "This trial caused a sensation 3 years ago," said Dr. Ravdin, referring to the fact that this was one of the first studies to show that zoledronic acid, a bisphosphonate used for osteoporosis and bone metastases, also had a benefit in breast cancer.

The results were impressive; zoledronic acid reduced the risk for breast cancer recurrence and breast cancer death by 33%, said Dr. Ravdin, but the results require interpretation. The patient population in the Austrian trial was very specific (premenopausal women treated with goserelin), and goserelin is not widely used in the United States, he commented in the past.

The new presentation this year will report on the continued follow-up in the ABCSG-12 trial.

The usefulness of bisphosphonates in the treatment of breast cancer may be further clarified by another presentation at SABCS this year — on the final results of the National Surgical Adjuvant Breast and Bowel Project (NSABP) Protocol B-34.

This trial compares adjuvant clodronate (Bonefos, Berlex) versus placebo in patients with early-stage breast cancer who are also treated with systemic chemotherapy and/or tamoxifen or no therapy. "This is the final analysis of the trial that asks the question: does the bisphosphonate clodronate have any impact on survival?" said C. Kent Osborne, MD, a co-director of the meeting, in an interview with Medscape Medical News. He is director of the Dan L. Duncan Cancer Center, Baylor College of Medicine, in Houston.

Clodronate is an oral bisphosphonate, which has the advantage of not causing osteonecrosis of the jaw (an adverse event associated with intravenous bisphosphonates), pointed out Dr. Ravdin.

In yet another bisphosphonate trial, new long-term results from the industry-sponsored ZO-FAST study will be presented. The presentation will cover survival outcomes among postmenopausal women with hormone receptor–positive early breast cancer who received adjuvant letrozole and zoledronic acid.

The studies presented to date suggest that the effect of zoledronic acid on breast cancer is complicated.

In 2010, one of the biggest stories at SABCS was the AZURE trial. The trial results showed no effect from zoledronic acid on the recurrence of breast cancer or overall survival. However, a subset analysis showed a significant effect on both recurrence and survival in postmenopausal women (more than 5 years after menopause), but no effect on premenopausal women.

Zoledronic acid does not appear to have a direct anticancer effect. The drug is administered by injection once every 6 months but is cleared from the system in about 24 hours. However, it persists in the bone and changes the bone marrow environment in such a way that the breast cancer cells are less likely to escape and cause a recurrence, an expert has previously told Medscape Medical News.

IOM, CLEOPATRA, and BOLERO-2

The new report from the Institute of Medicine is entitled "Breast Cancer and the Environment: A Life Course Approach" and assesses the breast cancer risk posed by various environmental factors. The report also identifies actions that might reduce women's risk for the disease and recommends targets for future research. The report is sponsored by Susan G. Komen for the Cure.

A new trial in patients with previously untreated HER2-positive metastatic or locally recurrent, unresectable breast cancer examines the potential benefit of treating patients with 2 targeted therapies instead of just 1. The results from the CLEOPATRA study are "long awaited," said Dr. Osborne.

The trial compares the safety and efficacy of the combination of pertuzumab (Roche) and trastuzumab (Herceptin, Roche) vs trastuzumab alone in these patients, all of whom also received docetaxel. Last year at SABCS, another study, known as NeoSphere, looked at this combination in the neoadjuvant setting and found that pertuzumab improved the activity of trastuzumab and docetaxel.

Another important trial in advanced breast cancer looks at the use of everolimus (Afinitor, Novartis). The drug is indicated for use in renal cell carcinoma and is also used to help prevent rejection in organ transplantation, said Dr. Ravdin. The results from this phase 3 trial, known as BOLERO-2, were presented at the recent European Multidisciplinary Cancer Congress. At that meeting, an expert said that "everolimus is the most important advance in breast cancer since trastuzumab." The results will be updated in San Antonio.

In BOLERO-2, investigators are comparing everolimus plus exemestane with exemestane alone in patients with estrogen-receptor-positive advanced breast cancer that is refractory to letrozole or anastrozole.

DCIS Study

In the treatment of DCIS, clinicians must advise patients about their possible need for radiation in addition to surgery; part of that conversation involves their risk for recurrence, said Dr. Ravdin. "Radiation strongly reduces the risk of local recurrence," he said, adding that the modality also had unwanted adverse effects. Thus, a tool that could help identify which patients have a low risk for recurrence and do not need radiation therapy could have a "huge and immediate impact," said Dr. Ravdin.

A new study to be presented this year at SABCS will provide some insight into one such potential tool, a multigene assay for DCIS from the makers of the Oncotype DX (Genomic Health), the multigene assay used to predict risk for recurrence in estrogen receptor–positive invasive disease.

The study is "really interesting" said Dr. Ravdin, and looks at patients with DCIS treated with surgery but not radiation. The study's primary objective is to determine whether there was a significant association between the risk for an ipsilateral breast event and the continuous DCIS score assessed by the gene assay.

34th Annual San Antonio Breast Cancer Symposium; December 6-10, 2011.

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