TAILORx

Background

Phase III RCT (TAILORx — Trial Assigning Individualized Options for Treatment). 10,273 women with hormone receptor-positive (HR+), HER2-negative, node-negative (pN0) breast cancer with an Oncotype DX recurrence score (RS) of 11–25 (intermediate range). Enrolled from 2006–2010 across North America and Australia. Randomized to chemoendocrine therapy vs endocrine therapy alone. Patients with RS ≤10 assigned to ET alone; RS ≥26 assigned to chemoET (not randomized). Primary aim: establish whether the intermediate RS group benefits from chemotherapy.

Interventions and follow up

Arm A: Chemoendocrine therapy (physician's choice chemotherapy + adjuvant endocrine therapy for ≥5 years)
Arm B: Endocrine therapy alone (no chemotherapy)
Primary endpoint: Invasive disease-free survival (iDFS) — non-inferiority
mFollow up: 90 months (median)

Results

9-year iDFS: 84.3% (chemo+ET) vs 83.3% (ET alone), HR 1.08 (95% CI 0.94–1.24), P=.26 — non-inferiority demonstrated
9-year OS: 93.9% vs 93.8%, HR 0.99 — not significantly different
9-year distant recurrence-free interval: 94.5% vs 95.0%, not significantly different
Subgroup: women <50, RS 16–25: Small absolute benefit from chemo in iDFS (HR ~0.80) and distant recurrence; clinically meaningful for decision-making

Adverse events

Main adverse events: Chemotherapy arm: Grade 3–4 hematologic toxicity (expected), fatigue, neuropathy, alopecia, menopausal symptoms accelerated. No chemotherapy arm: avoided cytotoxic toxicities. Long-term quality of life favored ET alone at 3 years. No excess contralateral breast cancer or other second malignancies with chemo.

Conclusions

For women with HR+, HER2−, N0 breast cancer and RS 11–25, endocrine therapy alone is non-inferior to chemoendocrine therapy for most patients. The only exception was women younger than 50 with RS 16–25, where a marginal benefit from chemotherapy was observed, supporting individualized decision-making in this subgroup.

Key Limitations

Key Limitations: Excluded patients with RS ≤10 (who clearly don't need chemo) and RS ≥26 (who should receive chemo) — these non-randomized groups represent ~35% of tested patients. Non-inferiority margin was pre-specified and somewhat broad. The age/RS interaction was a subgroup analysis. HER2-enriched and basal-like tumors may not be adequately represented in the intermediate RS range. Oncotype DX is a proprietary assay not universally accessible globally.

Clinical Context

TAILORx definitively established that most women with node-negative, HR+, HER2− breast cancer and intermediate Oncotype DX RS (11–25) can safely omit chemotherapy, sparing substantial toxicity for the majority. Together with RxPONDER (which addressed 1–3 positive nodes), Oncotype DX now guides chemotherapy decisions across a broad range of early-stage HR+ breast cancer. Though primarily an oncology trial rather than a radiation trial, it is relevant to multidisciplinary breast cancer management and treatment sequencing.

References

References: Sparano JA et al, N Engl J Med 2018 (TAILORx)