APT — Adjuvant Paclitaxel and Trastuzumab

Design, population and eligibility

Treatment and comparator

Intervention: Paclitaxel 80 mg/m² weekly for 12 weeks with trastuzumab (4 mg/kg loading then 2 mg/kg weekly during paclitaxel; subsequently trastuzumab 6 mg/kg every 3 weeks) to complete 1 year of anti-HER2 therapy.

Comparator: None. The single-arm design does not estimate comparative efficacy against observation or multi-agent chemotherapy.

Primary and secondary endpoints

Primary endpoint was 3-year invasive disease-free survival (iDFS). Long-term follow-up reported iDFS, recurrence-free interval (RFI), overall survival (OS) and breast cancer-specific survival (BCSS).

Key efficacy results

At 10.8 years, 10-year iDFS was 91.3% (95% CI 88.3–94.4), RFI 96.3% (95% CI 94.3–98.3), OS 94.3% (95% CI 91.8–96.8) and BCSS 98.8% (95% CI 97.6–100.0).

Among 31 iDFS events, six were ipsilateral locoregional recurrences, nine contralateral breast cancers, six distant recurrences and ten all-cause deaths. The 3-year iDFS in the original report was 98.7% (95% CI 97.6–99.8); 7-year DFS was 93% and 7-year RFI 97.5%.

Source-reported outcome visualization

Ten-year outcomes in the treated APT cohort · not a comparative treatment effect.

Kaplan–Meier estimates from the final 10-year analysis. RFI focuses on clinically relevant recurrence events; iDFS includes second primaries and deaths.

Absolute effect

No NNT or NNH is estimable: APT was single-arm and had no randomized comparator. The 10-year outcome rates are prognostic estimates under the regimen, not absolute treatment effects.

Trial-specific toxicity and treatment burden

In the initial safety report, grade 3–4 neuropathy occurred in 4%, neutropenia in 4%, transaminitis in 3%, leukopenia in 2%, fatigue in 2% and hypersensitivity reactions in 2%. Reversible symptomatic grade 3 left-ventricular systolic dysfunction occurred in 2 patients (0.5%).

356/406 (88%) completed all 52 weeks; 24 stopped for protocol-specified toxicity and six for other toxicities. Paclitaxel-associated neuropathy and one year of trastuzumab monitoring are the principal treatment burdens.

Quality of life and patient-reported outcomes

No randomized comparative QoL endpoint was reported. Patient-reported QoL benefit cannot be inferred from the single-arm efficacy results.

Subgroups and applicability

Most patients had HR-positive disease (67%). Exploratory HER2DX analyses associated a higher continuous risk score with worse iDFS (HR per 10-unit increment 1.24, 95% CI 1.00–1.52; p=0.047) and RFI (HR 1.45, 95% CI 1.09–1.93; p=0.011); this is prognostic exploration, not a validated treatment-selection interaction.

Current-practice context · reviewed 2 November 2026

The paclitaxel–trastuzumab approach remains a commonly used de-escalated adjuvant option for selected small node-negative HER2-positive tumours. Tumour size, nodal status, comorbidity and individual recurrence risk matter; the single-arm study does not establish equivalence to more intensive regimens in higher-risk disease.

Limitations and critical interpretation

Single-arm phase II design, modest cohort size, few breast-cancer events and no control group limit causal inference. iDFS includes events not necessarily attributable to the index breast cancer. The 10-year estimates should not be interpreted as a comparative absolute benefit.

Bottom line: APT supports a tolerable, less intensive adjuvant option for carefully selected small node-negative HER2-positive cancers, with excellent long-term breast cancer-specific outcomes; it does not prove non-inferiority to multi-agent chemotherapy.

Primary sources and follow-up publications

1. Tolaney et al. Final 10-year APT analysis, Lancet Oncology 2023
2. Tolaney et al. Initial APT report, NEJM 2015
3. APT trial registry

All outcome values above are transcribed from the linked trial reports or their prespecified follow-up publications. Unreported values are not imputed. No NNT is derived from median survival.