Highlight
– The SYSUCC‑001 trial reports a sustained 10‑year disease‑free survival (DFS) benefit with 1 year of metronomic capecitabine versus observation in operable triple‑negative breast cancer (78.1% vs 66.6%; HR 0.61; p=0.0074).
– Distant DFS and locoregional recurrence‑free survival were similarly improved; overall survival (OS) showed a strong trend but did not reach conventional significance at 10 years (HR 0.67; p=0.058).
– In a post‑hoc exploratory immunohistochemistry analysis, high tumour FOXC1 expression identified a subgroup with large DFS and OS benefits from capecitabine (DFS HR 0.33; OS HR 0.25).
Background: the unmet need in early triple‑negative breast cancer
Triple‑negative breast cancer (TNBC) accounts for approximately 10–20% of breast cancers and is characterized by absence of ER/PR expression and lack of HER2 amplification. TNBC has a higher risk of early recurrence and poorer long‑term survival than other subtypes. Contemporary adjuvant systemic therapy typically relies on cytotoxic chemotherapy; the optimal approach to further reduce late recurrences in patients with operable TNBC who have completed standard adjuvant therapy remains an area of active investigation.
Capecitabine, an oral prodrug of 5‑fluorouracil, has demonstrated benefit in several settings in breast cancer — most notably in the CREATE‑X trial where adjuvant capecitabine improved outcomes for patients with residual disease after neoadjuvant chemotherapy (a benefit particularly marked in TNBC). Metronomic dosing — low‑dose, continuous administration — is hypothesized to exert anti‑tumour effects through anti‑angiogenic, immune‑modulatory and direct cytotoxic mechanisms while maintaining tolerability for long durations. The SYSUCC‑001 trial evaluated whether 1 year of metronomic capecitabine given after completion of standard adjuvant therapy could reduce recurrence risk in early TNBC.
Study design
SYSUCC‑001 is an open‑label, multicentre, randomised phase 3 trial conducted at 13 centres in China. Women with operable triple‑negative breast cancer (T1b–T3, N0–N3c, M0) who had completed standard adjuvant therapy were randomised 1:1 to receive oral metronomic capecitabine 650 mg/m2 twice daily for 1 year or observation.
The original prespecified endpoints included disease‑free survival (primary), overall survival, distant disease‑free survival and locoregional recurrence‑free survival. An exploratory, post‑hoc biomarker analysis of FOXC1 expression by immunohistochemistry on baseline tumour samples was also performed. The trial registration is ClinicalTrials.gov NCT01112826.
Key findings (10‑year update)
Population and follow‑up: Between April 23, 2010, and Dec 31, 2016, 443 patients were enrolled and randomised; 434 initiated the assigned intervention and comprised the primary analysis set (221 capecitabine, 213 observation). As of data cutoff (March 31, 2025), 420 patients (97%) had follow‑up and median follow‑up was 116.0 months (IQR 96.0–134.8).
Primary outcome — disease‑free survival
At 10 years, DFS was significantly higher in the capecitabine arm: 78.1% versus 66.6% in the observation arm (hazard ratio [HR] 0.61; 95% CI 0.43–0.88; p=0.0074). This represents a durable absolute DFS difference of approximately 11.5 percentage points at 10 years and a 39% relative reduction in the hazard of recurrence or death.
Secondary outcomes — distant DFS, locoregional recurrence, overall survival
Distant disease‑free survival paralleled the DFS results: 10‑year distant DFS 78.1% versus 66.5% (HR 0.61; 95% CI 0.43–0.88; p=0.0075). Locoregional recurrence‑free survival at 10 years favored capecitabine (81.6% vs 69.9%; HR 0.60; 95% CI 0.40–0.89; p=0.011).
Overall survival at 10 years showed a numerical benefit with capecitabine (82.4% vs 73.7%) and a HR of 0.67 (95% CI 0.45–1.01; p=0.058) that narrowly missed conventional statistical significance. The pattern — significant reductions in DFS and distant recurrence with a strong OS trend — is biologically and clinically coherent but requires cautious interpretation.
Exploratory biomarker analysis — FOXC1
A biomarker cohort of 338 patients (78% of trial participants) underwent FOXC1 immunohistochemistry (171 capecitabine; 167 observation). Patients were stratified into FOXC1‑high (n=149) and FOXC1‑low (n=189) groups. In the FOXC1‑high subgroup, capecitabine was associated with markedly improved outcomes: DFS HR 0.33 (95% CI 0.16–0.68; p=0.0027) and OS HR 0.25 (95% CI 0.10–0.62; p=0.0028). By contrast, the FOXC1‑low subgroup derived no clear benefit from capecitabine versus observation.
Safety and tolerability
The primary publication of SYSUCC‑001 previously reported that metronomic capecitabine at 650 mg/m2 twice daily for 1 year was generally tolerable with expected capecitabine‑related adverse events (hand–foot skin reaction, gastrointestinal symptoms, cytopenias) manageable with dose adjustments and supportive care. The 10‑year update emphasises efficacy durability; no new late toxicities unique to extended follow‑up were highlighted in the report, but comprehensive long‑term safety tables were not the focus of this update.
Expert commentary and interpretation
Clinical significance: The SYSUCC‑001 10‑year results indicate that a pragmatic, low‑cost oral strategy — 1 year of metronomic capecitabine — can provide a clinically meaningful and durable reduction in recurrence risk for patients with operable TNBC. The absolute DFS gain (~11.5% at 10 years) and consistent reductions in distant and locoregional recurrences support the regimen’s activity in reducing both systemic and local relapse.
Comparison with prior evidence: The CREATE‑X trial (NEJM 2017) established adjuvant capecitabine as beneficial for patients with residual invasive disease after neoadjuvant chemotherapy, particularly in TNBC. SYSUCC‑001 differs in population and strategy: it tested extended adjuvant metronomic capecitabine after standard adjuvant therapy in an unselected post‑operative TNBC population. Together, these trials strengthen the evidence that capecitabine can meaningfully improve outcomes in certain TNBC contexts, though the patient selection, dosing regimen, and timing differ.
Biologic plausibility and FOXC1: FOXC1 is a transcription factor often associated with basal‑like phenotypes, more aggressive behaviour and poorer prognosis in breast cancer. The observation that FOXC1‑high tumours derived pronounced benefit from metronomic capecitabine is biologically plausible — these tumours may be more proliferative or have vulnerabilities that low‑dose continuous fluoropyrimidine exposure exploits. However, the FOXC1 analysis was post‑hoc, exploratory and limited to a subset of samples; assay standardisation and external validation are required before clinical application.
Limitations and cautions: Several important caveats temper immediate practice change.
- The biomarker findings are post‑hoc and hypothesis generating; multiplicity and selection biases may inflate apparent effects.
- SYSUCC‑001 was open‑label, which could potentially influence reporting of subjective endpoints, though DFS and survival are objective.
- The trial population was treated in China; while biologic behaviour of TNBC is broadly similar worldwide, differences in supportive care, subsequent lines of therapy, or population genetics could affect generalisability.
- OS benefit did not meet conventional statistical significance at 10 years despite strong trends; longer follow‑up or pooled analyses may clarify survival impact.
Clinical implications and practice considerations
For clinicians managing early TNBC, SYSUCC‑001 offers data supporting a low‑cost, oral extended adjuvant option that reduces recurrence risk when given for 1 year after standard adjuvant therapy. Implementation should consider individual patient factors: comorbidities, performance status, potential toxicity (especially hand–foot syndrome), convenience and patient preference.
Routine FOXC1 testing to select patients cannot be recommended yet. The FOXC1 signal is provocative and could guide future enrichment strategies, but requires prospective validation (ideally in a randomised biomarker‑stratified trial or robust external cohorts with pre‑specified cutpoints and standardised assays).
Research priorities
Key next steps include:
- Prospective validation of FOXC1 as a predictive biomarker in independent cohorts and standardisation of IHC scoring or gene expression assays.
- Randomised trials comparing metronomic capecitabine against other adjuvant strategies or in biomarker‑selected populations to confirm magnitude of benefit and impact on OS.
- Translational studies to define mechanisms by which metronomic fluoropyrimidines preferentially impact FOXC1‑high or basal‑like tumours (angiogenesis, immune modulation, tumour cell chemosensitivity).
- Health‑economic analyses to quantify cost‑effectiveness of a 1‑year oral regimen in diverse health systems.
Conclusion
The 10‑year SYSUCC‑001 update demonstrates that 1 year of metronomic capecitabine after completion of standard adjuvant therapy yields a durable DFS benefit for patients with early TNBC, with concordant improvements in distant and locoregional control and a strong OS trend. An exploratory FOXC1 biomarker analysis suggests a large treatment effect in FOXC1‑high tumours, but this finding is hypothesis‑generating and requires prospective validation. Until then, clinicians may consider extended metronomic capecitabine as a pragmatic option for selected patients after weighing toxicity, patient preference and existing evidence.
Funding and trial registration
SYSUCC‑001 was funded by the National Natural Science Foundation of China and the Guangdong Esophageal Cancer Institute Science and Technology Program. ClinicalTrials.gov NCT01112826.
References
1) Yuan J, Bi XW, Hua X, et al. Metronomic capecitabine as extended adjuvant chemotherapy for early triple‑negative breast cancer (SYSUCC‑001): updated 10‑year outcomes and post‑hoc exploratory biomarker analysis from a randomised, phase 3 trial. Lancet Oncol. 2025 Dec;26(12):1575-1583. doi: 10.1016/S1470-2045(25)00545-5. PMID: 41308674.
2) Masuda N, Lee SJ, Ohtani S, et al. Adjuvant capecitabine for breast cancer after preoperative chemotherapy. N Engl J Med. 2017;376:2147–2159. (CREATE‑X)
Additional context and guideline resources: refer to contemporary guideline documents (e.g., NCCN, ESMO) for integration of capecitabine into adjuvant management pathways of early breast cancer.
