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.

Administration of adjuvant trastuzumab reduced the risk of developing local recurrence in women with small HER2-positive breast cancer, according to the results of a retrospective multicenter study presented at the 17th St. Gallen International Breast Cancer Conference 2021.

“Adjuvant targeted therapy should be considered in patients with hormone receptor-negative HER2 positive breast cancer since they have the highest risk of recurrence, independently from size and grade,” Andrea Villasco, of A.O. Ordine Mauritziano, University of Turin, Italy, and colleagues wrote in the poster presented at the conference.

The researchers measured the efficacy of trastuzumab in early-stage breast cancer in 100 patients (23 received trastuzumab) with HER2-positive disease diagnosed from January 1998 to December 2018. The primary outcome was breast cancer recurrence rate.

When comparing patients who had microinvasive pathologic T1 tumors (pT1mi; tumor size ≤1 mm) vs pT1a (tumor size 1-5 mm), pT1mi showed lower expression of hormone receptors, high tumor grade, and elevated Ki-67 index.


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With a median follow-up of 86 months, the disease recurrence rate was found to be significantly lower among patients who received adjuvant trastuzumab compared with those who did not (4.3% vs 25.9%; P=.02). This equated to an 85% reduction in risk of recurrence (hazard ratio [HR]=0.15; 95% CI, 0.02-1.19).

Among the group of patients who did not receive adjuvant trastuzumab, the molecular subtype was significantly associated with an increased risk of developing recurrence. Specifically, patients with hormone receptor-negative, HER2-positive disease were found to have a 7-fold higher risk for relapse (HR=7.29; 95% CI, 1.68-31.60).

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Reference

Villasco A, Actis S, Borella F, et al. Evaluation of the efficacy of trastuzumab in patients with HER2 positive small (pT1mi/a) breast cancers. A multicenter retrospective study on 100 patients. Poster presentation at: 17th St. Gallen International Breast Cancer Symposium 2021; March 17-21, 2021. Abstract P002.