KEY POINTS
- STAR-TREC is an international phase 2/3 trial conducted at 37 centers in five European countries in patients with MRI-defined T1–T3b N0 rectal adenocarcinoma ≤40 mm. For this interim report, the modified intention-to-treat population included 409 patients: 163 allocated to long-course chemoradiotherapy-based organ preservation, 168 to short-course RT-based organ preservation, and 78 to primary total mesorectal excision.
- Long-course treatment consisted of 50 Gy in 25 fractions plus capecitabine 825 mg/m² twice daily on radiation days. Short-course treatment used 25 Gy in five fractions without consolidation chemotherapy. Both strategies used mesorectal-only target volumes and the same prespecified response-adapted pathway.
- At 12 months, TME-free survival was 78.5% with long-course chemoradiotherapy versus 60.6% with short-course RT, an absolute difference of 17.9 percentage points; the reported hazard ratio was 1.90 (95% CI 1.29–2.81), with a posterior probability of long-course superiority >99.5%.
- Tumor response was also substantially deeper after long-course treatment. At 16–20 weeks, clinical complete response occurred in 64% versus 36%, while transanal local excision for near-complete response was needed in 23% versus 40% with long-course versus short-course treatment.
- Conversion to TME before surveillance occurred in 17% with long-course treatment versus 33% with short-course RT. Persistent ypT2–3 disease was likewise less common after long-course treatment (15% vs 37%), as was pathologic nodal involvement (4% vs 8%).
- Early oncologic outcomes remained similar: no notable differences were seen at 12 months in pelvic tumor control, metastasis-free survival, disease-free survival, or overall survival. All 19 delayed salvage TME procedures performed during the first year achieved clear resection margins.
- Serious grade ≥3 adverse events over 12 months occurred less often with either organ-preservation strategy than with primary surgery. Grade 3/4/5 events occurred in 7%/1%/0% with long-course treatment, 8%/1%/0% with short-course RT, and 14%/3%/1% with primary TME; one postoperative death followed an anastomotic leak in the TME group.
CLINICAL TAKEAWAY
For selected early- and intermediate-stage rectal cancers suitable for organ preservation, long-course chemoradiotherapy produced substantially more complete responses and fewer early TMEs than short-course RT. The signal is clinically important, but these are 12-month interim results; durable organ preservation, local regrowth and long-term oncologic safety await the prespecified 30-month and later analyses.