The Co-Directors of the 2013 CTRC-AACR San Antonio Breast Cancer Symposium, which will be held December 10–14, 2013, have highlighted what they consider to be the most important abstracts to be presented at the Symposium. In a telebriefing in advance of the December meeting, C. Kent Osborne, MD, called these the “abstracts to keep an eye on.”

The meeting, now in its 36th year, is the largest of its kind devoted exclusively to breast cancer research and draws more than 8,000 people, including basic scientists, clinicians, advocates, and news media. It is an annual collaboration of the Cancer Therapy & Research Center (CTRC) at The University of Texas Health Science Center at San Antonio, the American Association for Cancer Research (AACR), and Baylor College of Medicine.

Screening and Locoregional Therapy

The value of mammographic screening has been controversial. A meta-analysis (Abstract S1-10) of four pivotal mammographic screening studies, by an international consortium, is a re-analysis of the data that aims for consistency. “I think this paper will come up with some interesting data on the value of mammography, and will address an issue that has become important—over-diagnosis—and whether it’s a problem with regard to these studies,” said Dr. Osborne, Director of the Dan L. Duncan Cancer Center and Director of the Lester and Sue Smith Breast Center at Baylor College of Medicine, Houston.

Other highlighted studies in the area of locoregional therapy will address the need for radiotherapy after breast-conserving therapy in women aged 65 and older (S2-01) and the value of resecting the primary tumor in metastatic patients, according to two prospective studies (S2-02, S2-03).

Endocrine Therapy

Endocrine therapy will be of particular interest at the meeting, with a number of clinically meaningful presentations, Dr. Osborne said. Investigators will examine the benefit and toxicity of anastrozole in preventing breast cancer in the IBIS-2 trial (S3-01), the association between baseline symptoms and discontinuation of adjuvant endocrine therapy (S3-02), the effect of exercise on ameliorating arthralgia (S3-03), the effect of mutations in the estrogen receptor on emergence of treatment resistance (S3-06), and the efficacy of dasatinib (Sprycel) when combined with letrozole (S3-07).

Novel Topics, New Agents to Be Explored

Peter Ravdin, MD, PhD, breast cancer researcher and biostatistician in San Antonio, Texas, highlighted abstracts that will advance the understanding of the role of the immune system in fighting breast cancer. Three such studies pertain to tumor infiltrating lymphocytes (S1-05, S1-06, S1-07), which could prove to be prognostic. “These papers are an exciting and interesting lead,” he said.

New agents on the radar at the symposium include palbociclib, the CDK 4/6 inhibitor that has received Breakthrough Therapy designation from the U.S. Food and Drug Administration (FDA). Palbociclib was impressive in a phase II trial reported at this meeting last year, according to Dr. Ravdin, and this year attendees will hear the results of a biomarker analysis (P2-16-20). Several ongoing studies of the drug will also be described (OT3-2-10, OT2-6-11, OT2-6-01).

The question of whether bisphosphonates may help reduce recurrences will be informed by a meta-analysis of nearly 15,000 patients, a late-breaking abstract. And questions regarding the value of using circulating tumor cells in assessing outcomes may be answered by SWOG S0500 (S5-07). “This study could definitively make clear if circulating tumor cells could be used to better tailor therapy, and this could change the standard of care,” Dr. Ravdin said.

Neoadjuvant Setting

Carlos L. Arteaga, MD, indicated that a number of neoadjuvant trials will be informative and relevant, in light of the FDA’s position that drugs for HER2-positive and triple-negative breast cancer might be considered for approval, based on findings in the preoperative setting.

Dr. Arteaga is President-Elect of the American Association for Cancer Research and Associate Director for Translational/Clinical Research and Director of the Breast Cancer Program at Vanderbilt-Ingram Comprehensive Cancer Center in Nashville.

An analysis from NeoALTTO trial will report the correlation between pathologic complete response and long-term event-free survival (S1-01). NeoALTTO is evaluating neoadjuvant lapatinib (Tykerb), trastuzumab (Herceptin), or their combination in HER2-positive patients. “A positive correlation should generate excitement,” Dr. Arteaga predicted.

The same anti-HER2 agents will be paired with docetaxel plus carboplatin in another study called TRIO, deemed important especially for its data on toxicity (S1-02), he said.

The first efficacy results for the PARP inhibitor, veliparib, given with carboplatin and standard neoadjuvant therapy to high-risk patients, will come from the much-heralded, adaptive-design I-SPY2 trial (S5-02). Another paper will look at the prognostic value of residual cancer burden after neoadjuvant treatment (S6-02) and perhaps help clarify which patients are at a particularly high risk of recurrence and, as such, need novel therapies to prevent these recurrences.

Important Adjuvant Studies

Dennis Slamon, MD, PhD, Professor, Chief, and Executive Vice Chair for Research, Department of Medicine, Hematology/Oncology, at UCLA’s Jonsson Comprehensive Cancer Center, will be a much-anticipated speaker as he presents the primary results of the phase III BETH study of adjuvant chemotherapy and trastuzumab with or without bevacizumab (Avastin) in patients with HER2-positive, node-positive, or high-risk node-negative breast cancer (S1-03). Following Dr. Slamon, Sara M. Tolaney, MD, MPH, of Dana-Farber Cancer Institute, Boston, will report follow-up of a large single-arm study in patients with small HER2 tumors treated with trastuzumab and chemotherapy (S1-04).

PIK3CA Mutations

Mutations in the PI3 kinase pathway are the most frequent mutations in breast cancer, therefore, interest in these mutations is very high, Dr. Arteaga indicated. Investigators from the GeparSixto and GeparQuinto trials will report whether the PIK3CA mutation predicts resistance to anti-HER2/chemotherapy in HER2-positive, hormone receptor–positive tumors, and triple-negative tumors. Other researchers will report on novel approaches to discover ways of overcoming resistance to PI3K inhibitors, which are in development (S4-04, S4-05, S4-06).

Finally, a relatively new topic, which may be important for triple-negative tumors, will be JAK2 amplification, its association with worse outcomes after neoadjuvant treatment, and associated clinical implications as JAK2 inhibitors are currently in development (S6-01). ■

Disclosure: Drs. Arteaga, Osborne, and Ravdin reported no potential conflicts of interest.