Long-term results from the APT trial support the use of adjuvant paclitaxel and trastuzumab in patients with small, node-negative, HER2-positive breast cancer, according to researchers.
The researchers also found the HER2DX genomic tool was able to identify a subset of these patients at increased risk of recurrence. The findings were published in The Lancet Oncology.
The phase 2 APT trial (ClinicalTrials.gov Identifier: NCT00542451) included 406 patients with small (≤3cm), node-negative, HER2-positive breast cancer. The patients’ mean age at enrollment was 55 years, 99.8% of patients were women, 86.2% were White, and 18.7% were premenopausal at baseline.
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The patients received intravenous paclitaxel plus trastuzumab weekly for 12 weeks, followed by trastuzumab weekly or once every 3 weeks for 40 weeks. Patients who underwent breast-conserving surgery received either partial-breast irradiation before study treatment or whole-breast irradiation after completing paclitaxel. Patients with hormone receptor-positive disease could receive adjuvant endocrine therapy after completing paclitaxel.
The median follow-up was 10.8 years. There were 31 invasive disease-free survival events. Ten of the events were all-cause deaths, 9 were new contralateral breast cancers (1 HER2-positive), 6 were locoregional ipsilateral recurrences, and 6 were distant recurrences.
At 10 years, the invasive disease-free survival rate was 91.3%, the recurrence-free interval was 96.3%, the overall survival rate was 94.3%, and the breast cancer-specific survival rate was 98.8%.
The researchers also conducted an exploratory analysis in 284 patients using the HER2DX genomic tool. The tool suggested that 4.9% of patients had high-risk disease.
HER2DX risk score as a continuous variable was significantly associated with invasive disease-free survival (hazard ratio [HR] per 10-unit increment, 1.24; 95% CI, 1.00-1.52; P =.047) and recurrence-free survival (HR per 10-unit increment, 1.45; 95% CI, 1.09-1.93; P =.011).
The researchers also identified a HER2DX risk score of 32 as the optimal cutoff to separate patients with low-risk disease from those with high-risk disease in this trial.
“[T]his end-of-study, 10-year analysis of the APT trial supported that adjuvant treatment with paclitaxel and trastuzumab produces very good long-term outcomes for patients with small, node-negative, HER2-positive breast cancer,” the researchers wrote. “HER2DX testing proved promising in the identification of a subset of tumors with a relatively high risk of recurrence, and, if validated, might aid in the tailoring of adjuvant treatments for patients with stage 1 HER2-positive breast cancer.”
Disclosures: This research was supported by Genentech. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Reference
Tolaney SM, Tarantino P, Graham N, et al. Adjuvant paclitaxel and trastuzumab for node-negative, HER2-positive breast cancer: Final 10-year analysis of the open-label, single-arm, phase 2 APT trial. Lancet Oncol. Published online March 2023. doi:10.1016/S1470-2045(23)00051-7
