The following article is part of conference coverage from the 17th St. Gallen International Breast Cancer Symposium, which is being held virtually from March 7-21, 2021. The team at Cancer Therapy Advisor will be reporting on the latest research conducted by leading experts in breast cancer. Check back for more from the 17th St. Gallen International Breast Cancer Symposium.

Triple-negative breast cancer (TNBC) and HER2-positive (HER2+) breast cancer were found to be associated with a higher pathologic complete response (pCR) rate following neoadjuvant chemotherapy, according to research presented at the 17th St. Gallen International Breast Cancer Conference 2021.

Bernardo Rapoport, MD, from the Medical Oncology Centre of Rosebank in Johannesburg, South Africa, and colleagues retrospectively analyzed data from 273 patients with early breast cancer who were undergoing neoadjuvant chemotherapy. The patients’ primary tumor and lymph nodes were clinically assessed, and sonographic assessments were conducted at baseline and at regular intervals afterward.

The researchers defined pCR as the complete disappearance of invasive cancer in the breast and absence of tumor in the axillary lymph nodes. Fisher exact or chi-square tests were used to analyze categoric variables, and logistic regression multivariate models included only variables that showed a univariate association with the dependent variable, pCR (P <.1).

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Among the cohort (median age, 52 years; range, 26-89), luminal A subtype was documented in 12 participants (4.4%), luminal B in 55 participants (20.15%), HER2+ in 44 patients (16.12%), and TNBC in 162 patients (59.34%).

The pCR rate for the total cohort was 48%. At 4 years, 96% of participants who achieved a pCR were disease free compared with 74% of those who did not attain a pCR.

According to univariate analysis, factors associated with higher pCR included molecular subtype (TNBC [60%], HER2+ [61%], luminal A [none], and luminal B [15%], chi-square, 48; P <.00000); primary tumor size (T1 [66%] vs T2 [49%] vs T3 [19%] vs T4 [27%], chi-square, 19.70; P <.0002); nodal disease (N0 [56%] vs N1 [40%], chi-square, 7.05; P <.007); age (<50 years [55%] vs ≥50 years [43%], chi-square, 3.75; P <.05); estrogen receptor status (negative [61%] vs positive [26%], chi-square, 31.56; P <.00000); progesterone receptor status (negative [59%] vs positive [19%], chi-square, 33.95; P <.00000); Ki67 (≥40 [60%] vs 14-39 [41%] vs ≤14 [5%], chi-square, 27.11; P <.00001); and stage (I [77%] vs IIA [55%] vs IIB [40%] vs III [24%], chi-square, 23.89; P <.00003). Menopausal status, ethnicity, extranodal spread, and lympho-vascular invasion were not associated with a higher pCR rate.

Logistic regression analysis demonstrated that Ki67 as a continuous variable (P <.0073) and biologic subtype (P <.0003) retained their significance, but tumor size, stage of disease, nodal status, estrogen receptor status, and progesterone receptor status lost significance.

“These data highlight the importance of breast care multidisciplinary management in early disease,” the study authors concluded. “TNBC and HER2+ subsets were associated with a higher pCR rate. These results are similar to those reported in a clinical trial setting.”

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Rapoport BL, Smit T, Heyman L, et al. Her-2 positive and TNBC patients receiving neoadjuvant chemotherapy are associated with a high pathological complete response rate — results from real-world outcomes in a multidisciplinary setting. Poster presented at: 17th St. Gallen International Breast Cancer Conference 2021; March 17-20, 2021. Abstract P082.