Less Is More: The APT Trial at 10 years

HER2-positive breast cancer is viewed as an aggressive subtype, yet the introduction of numerous HER2-directed therapies in recent years has significantly improved the outcome of patients with both early- and late-stage disease. Combinations of chemotherapy with HER2-directed agents, often multidrug combinations, have become standard adjuvant regimens for early-stage breast cancer. When the adjuvant paclitaxel and trastuzumab (APT) regimen was first reported almost a decade ago, it offered the prospect of excellent results for patients with lower risk, axillary node–negative breast cancer with a less toxic and simpler combination of drugs; APT represented de-escalation.

Now, investigators report the final 10-year analysis of the APT trial, an industry-funded, open-label, single-arm, phase 2 study of 406 adults with small (≤3 cm), node-negative, HER2-positive breast cancer. Patients received paclitaxel and trastuzumab weekly for 12 weeks followed by trastuzumab for 1 year.

At a median follow-up of 10.8 years, there were 31 invasive disease-free survival (iDFS) events, including 10 all-cause deaths, 9 new contralateral breast cancers, 6 locoregional ipsilateral recurrences, and 6 distant recurrences. The 10-year iDFS was 91.3%, the 10-year recurrence-free interval was 96.3%, the 10-year overall survival was 94.3%, and the 10-year breast cancer–specific survival was 98.8%.

The HER2DX genomic test, based on the expression of three gene signatures (tracking immune or immunoglobulin features, tumor cell proliferation, and luminal differentiation) was conducted on available RNA from baseline archived tissue samples. An exploratory analysis identified a small subset of patients with a high HER2DX score or a luminal B intrinsic subtype who may have an increased risk for recurrence.