SABCS 2016: No Added Benefit With Aromatase Inhibitor as Part of Presurgical Therapy for Hormone Receptor–Positive, HER2-Positive Breast Cancer
Adding an aromatase inhibitor to presurgical treatment with docetaxel, carboplatin, trastuzumab (Herceptin), and pertuzumab (Perjeta) did not significantly increase or decrease the percentage of patients with hormone receptor–positive, HER2-positive breast cancer who had a pathologic complete response, according to data from a phase III clinical trial (NRG oncology/NSABP B-52) presented at the 2016 San Antonio Breast Cancer Symposium, held December 6–10 (Abstract S3-06).
“Many patients with [hormone receptor]–positive, HER2-positive breast cancer who have large, operable breast tumors or evidence that the cancer has spread to underarm lymph nodes receive docetaxel, carboplatin, trastuzumab, and pertuzumab before surgery,” said Mothaffar F. Rimawi, MD, Associate Professor and Medical Director at the Lester and Sue Smith Breast Center, part of the Dan L Duncan Comprehensive Cancer Center at Baylor College of Medicine. “However, many of them don’t respond optimally, especially if their tumors are also [hormone receptor]–positive. Preclinical and clinical data led us to test whether adding an aromatase inhibitor to this neoadjuvant treatment regimen in this patient group would increase the percentage of patients who have a [pathologic complete response].”
Trial Details
Dr. Rimawi and colleagues randomly assigned 315 patients with operable, locally advanced [hormone receptor]–positive, HER2-positive breast cancer 1:1 to neoadjuvant docetaxel, carboplatin, trastuzumab, and pertuzumab treatment with or without an aromatase inhibitor. Premenopausal women randomly assigned aromatase inhibitor therapy also received ovarian function suppression with goserelin (Zoladex) or an equivalent agent.
Among 308 patients who were randomly assigned docetaxel, carboplatin, trastuzumab, pertuzumab, plus an aromatase inhibitor, 71 (46.1%) had a pathologic complete response. Of 154 patients who were randomly assigned docetaxel, carboplatin, trastuzumab, pertuzumab, and no aromatase inhibitor, 63 (40.9%) had a pathologic complete response.
“We saw a modest numerical increase in the number of patients who had a [pathologic complete response] in the aromatase inhibitor arm of the study, but the increase was not statistically significant. There had been concern that chemotherapy and endocrine therapy may have antagonistic effects. We did not see that,” said Dr. Rimawi.
Study Implications
“At this point, we cannot recommend a change to the standard-of-care neoadjuvant treatment regimen for patients with [hormone receptor]–positive, HER2-positive breast cancer,” he continued, “but the [tested] combination was safe and well-tolerated. We are further analyzing tissue samples from the patients to investigate whether there are subgroups of patients who might benefit from the inclusion of an aromatase inhibitor in the neoadjuvant setting.”
Dr. Rimawi concluded, “Ultimately, we would like to deescalate treatment for as many patients as it is safely possible to do so. Discovering which patients need more therapy and which patients need less is crucial. Correlative studies from this and our other research efforts will provide critical information to move in that direction.”
The proportion of patients who had grade 3 or grade 4 adverse events was similar among those whose neoadjuvant treatment included an aromatase inhibitor.
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