San Antonio Breast Cancer Symposium, Dec. 6-10

In the phase II TRIO-US B-12 TALENT clinical trial, Aditya Bardia, M.D., of the Massachusetts General Cancer Center and Harvard Medical School in Boston, and colleagues found that neoadjuvant trastuzumab deruxtecan (T-DXd) demonstrates efficacy in patients with localized, hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-low breast cancer, with a toxicity profile consistent with previous reports.

The data presented included 17 patients who had completed the planned eight cycles of T-DXd and 16 patients who had completed the planned six cycles of T-DXd plus anastrozole. The researchers found that T-DXd showed preliminary evidence of clinical activity in HER2-low, HR-positive localized breast cancer, with a toxicity profile consistent with previous reports. The objective response rate was 68 percent with T-DXd alone and 58 percent with T-DXd and anastrozole. The addition of endocrine therapy to T-DXd did not appear to enhance efficacy, but caution needs to be exerted in drawing strong conclusions given the small sample size. Furthermore, dynamic changes in HER2 tissue expression were noted after treatment with T-DXd.

“This study provides a rich platform for translational research to evaluate more sensitive methods of HER2 detection, develop predictive biomarkers, and understand mechanisms of resistance in residual disease to guide future therapeutic strategies, including combination therapy, for patients with early breast cancer,” Bardia said.

Several authors disclosed financial ties to pharmaceutical companies, including Daiichi Sankyo, which manufactures T-DXd and funded the study

As part of the RxPONDER clinical trial, Yara Abdou, M.D., of the University of North Carolina and Lineberger Comprehensive Cancer Center in Chapel Hill, and colleagues found that non-Hispanic Black women with HR-positive/HER2-negative, lymph node-positive breast cancer experience worse outcomes compared with non-Hispanic White, Asian, and Hispanic women, despite similar genetic recurrence scores (RS).

The authors aimed to evaluate the value of the 21-gene RS among 4,048 women with HR-positive/HER2-negative breast cancer who had one to three positive axillary lymph nodes and RS of 25 or lower. The researchers found that non-Hispanic Black women with HR-positive/HER2-negative breast cancer with one to three involved lymph nodes and RS ≤25 had worse outcomes compared with non-Hispanic White women, independent of RS, treatment arm, age, and grade.

“Our study results, similar to prior studies, indicate racial disparities in breast cancer, particularly in hormone receptor-positive breast cancer,” Abdou said. “This highlights that further progress needs to be made to improve outcomes for Black women with breast cancer, starting with greater representation of racial and ethnic minorities in clinical trials to help further understand cancer disparities and ultimately improve outcomes for minority women with breast cancer.”

Judy C. Boughey, M.D., of the Mayo Clinic in Rochester, Minnesota, and colleagues found that breast-conserving therapy is an appropriate treatment option for women with multiple ipsilateral breast cancer.

The authors evaluated whether breast conservation with lumpectomy followed by radiation therapy is an appropriate management for patients who have more than one tumor in a single breast. The researchers found that for patients with two or three foci of breast cancer in the breast, breast-conserving therapy is a reasonable treatment option. With breast-conserving surgery followed by whole breast radiation with radiation boost to all lumpectomy sites, the five-year local recurrence rate was 3.1 percent. The local recurrence rate was lower in patients who had preoperative breast magnetic resonance imaging (MRI) and in those patients with estrogen receptor (ER)-positive breast cancer who received adjuvant endocrine therapy.

“This study provides important data for surgeons and radiation oncologists to discuss with their patients who have two or three foci of breast cancer in one breast and allows patients to consider their preference between breast conservation therapy and mastectomy,” Boughey said. “Breast conservation therapy is often preferred to mastectomy as it is a smaller operation with quicker recovery and results in better patient satisfaction and cosmetic outcomes. We hope that this will result in patients with multiple ipsilateral breast cancer to consider breast-conserving therapy if they are interested.”

Ruth O’Regan, M.D., of the University of Rochester in New York, and colleagues found that the genomic assay called the Breast Cancer Index (BCI) is able to distinguish between women who will and will not receive benefit from adding ovarian function suppression (OFS) to primary adjuvant endocrine therapy.

The authors evaluated the BCI in a subset of 1,687 patients enrolled in the Suppression of Ovarian Function Trial to determine whether BCI can predict prognosis and benefit from OFS in premenopausal women with HR-positive, early-stage breast cancer who received endocrine therapy with or without chemotherapy. The researchers determined that the BCI was able to identify which premenopausal women with early-stage, HR-positive breast cancer benefited from the addition of OFS to primary adjuvant endocrine therapy. The study results also confirmed that the BCI is prognostic for the likelihood of distant recurrence in HR-positive premenopausal patients receiving adjuvant endocrine therapy.