What's New at World's Biggest Breast Cancer Meeting

Nick Mulcahy

November 30, 2016

The largest meeting of its kind, the 2016 San Antonio Breast Cancer Symposium (SABCS) will feature a wide array of studies in the treatment and management of one of the world's most common malignancies.

This year's hot — and varied — topics and studies include:

  • Duration of treatment length of endocrine therapy;

  • Optimal candidates for human epidermal growth factor receptor 2 (HER2)–targeted therapy;

  • First-ever randomized controlled trial of a scalp-cooling device to prevent hair loss in patients receiving chemotherapy;

  • Comparison of cancer patients' evaluation by machine (IBM's Watson technology) vs clinicians on a cancer center tumor board; and

  • Concurrent use of endocrine therapy with chemotherapy in HER2-positive and estrogen receptor (ER)–positive disease.

The duration of endocrine therapy for hormone-receptor–positive disease is a an area of ongoing research in oncology, said C. Kent Osborne, MD, director of the Dan L. Duncan Comprehensive Cancer Center at the Baylor College of Medicine in Houston, Texas, and an SABCS director.

"How long should we continue these drugs?" is a major question for clinicians, Dr Osborne said in an interview with Medscape Medical News.

Past research has indicated that 10 years of tamoxifen has benefits over 5 years. This past summer, a major study (MA-17R) presented at the American Society of Clinical Oncology annual meeting indicated that extending treatment with the aromatase inhibitor (AI) letrozole to 10 years after an initial 5 years of therapy with an endocrine therapy improves disease-free survival (but not overall survival).

At this year's SABCS, investigators of the similarly designed phase 3, NRG Oncology/NSABP B-42 trial will report results on using letrozole after completion of 5 years hormonal therapy (consisting of an AI or tamoxifen) in this same setting — postmenopausal women with hormone receptor–positive breast cancer.

 
It's really a trial we have been waiting for. Dr C. Kent Osborne
 

"It's really a trial we have been waiting for," said Dr Osborne.

"If this has positive results, it will really put the nail in the coffin, so to speak, that, for many patients, not only is prolonged tamoxifen better but so is a prolonged aromatase inhibitor," he added.

The meeting will also feature a presentation on the phase 3 DATA study comparing 3 vs 6 years of anastrozole after 2 to 3 years of tamoxifen in this same setting.

About these endocrine trials, Dr Osborne said, "This is a group of abstracts that may potentially be practice changing or may solidify what some doctors are already doing."

Clinicians may receive some important clinical insights about which patients are optimal recipients of HER2-targeted therapy from the PAMELA clinical trial, said Dr Osborne.

The new study looks at the PAM50 intrinsic subtype as a predictor of pathologic complete response (pCR) following neoadjuvant dual HER2 blockade without chemotherapy in HER2-positive breast cancer.

Dr Osborne explained how many centers currently assess patient suitability for HER2-targeted drugs.

"Right now, to use Herceptin and other HER2-targeted therapies, we require a fluorescence in situ hybridization (FISH) ratio of greater than 2…and that has been used in a somewhat arbitrary way to predict response," he said.

Dr Osborne forecasts that "more and more data" are going to show that "a higher level of amplification" is needed to justify use of HER2-targeted therapies.

The PAMELA study alone will not change practice, but other data are also "cooking" and if they, in sum, show that lower levels of HER2 amplification are not associated with clinical benefit, then practice will change, he predicted.

Women treated with chemotherapy for breast cancer typically have hair loss, which is often cited as traumatic by patients. At this year's meeting, investigators of the Scalp Cooling Alopecia Prevention (SCALP) trial will present initial efficacy data on preventing hair loss in patients with early-stage disease. Dr Osborne said he was a study investigator, cited his conflict of interest, and commented only that this is the first-ever randomized trial of a scalp-cooling device to prevent hair loss in the United States.

The story behind the creation of the Paxman Scalp Cooling System was covered by Medscape Medical News at last year's SABCS.

There will also be another first-of-its kind study this year — of the IBM artificial intelligence platform known as Watson, which has been used in US clinics in a limited manner for a few years. At this year's meeting, researchers will present a double-blinded validation study of the first 638 breast cancer cases analyzed by Watson; its performance is compared against that of a multidisciplinary tumor board at the Manipal Hospital, a cancer center in Bangalore, India.

Question Over Adding Endocrine Therapy to Chemo

In medical oncology, there has been a prohibition against using endocrine therapy concurrently with chemotherapy in patients with breast cancer, according to Dr Osborne.

The prohibition was evidence-based, but only in part. "For the longest time, based on studies that I did in the 1980s, adding tamoxifen to certain chemotherapy drugs was antagonistic," he said, meaning it diminished the latter's effectiveness.

"We have never given endocrine therapy with chemotherapy since that time," he said.

But the prohibition went beyond what Dr Osborne's research indicated.

"We routinely assumed that this would apply not only to tamoxifen, but to other endocrine therapies — that is, you shouldn't give them at exactly the same time [along with chemo] in the adjuvant setting."

"I don't think that is right," he said, but added that data are needed to prove it.

The data may have arrived this year from the above-mentioned NRG Oncology/NSABP B-42 trial.

This phase 3 trial evaluates pCR in patients with hormone receptor–positive, HER2-positive breast cancer treated with neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab with or without estrogen deprivation.

Dr Osborne said that clinicians need to know whether there is antagonism when starting patients on an AI in combination with chemotherapy and HER2-targeted therapies.

Combination targeted HER2 therapy is now standard, especially for metastatic disease; chemotherapy is also added in most higher-risk patients. But with women with hormone receptor–positive disease, there had been a nagging concern about administering endocrine therapy at the same time, he said.

 
There is all this worry. Dr C. Kent Osborne
 

"There is all this worry that adding the endocrine therapy to the HER2-targeted therapy would antagonize the effect of the chemotherapy drugs [such as docetaxel]," Dr Osborne commented.

He predicted that the trial will "probably not show an advantage" with the addition of endocrine therapy because results are already "so good" in this setting. "But it's probably not going to show a disadvantage," he added.

"Since the estrogen receptor is there and provides an immediate escape to HER2 blockade, the idea is you've got to block both," said Dr Osborne about the mechanics of adding the endocrine therapy (in this case, letrozole).

Dr Osborne has disclosed no relevant financial relationships.

Follow Medscape senior journalist Nick Mulcahy on Twitter: @MulcahyNick

Follow Medscape Oncology on Twitter: @MedscapeOnc

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