STAR-TREC
STAR-TREC: Can we Save the Rectum by Watchful Waiting or TransAnal Surgery Following (Chemo)Radiotherapy Versus Total Mesorectal Excision for Early REctal Cancer?
Phase 2/3N = 503NCT02945566
- Population
- Adults with rectal adenocarcinoma up to 40 mm staged mrT1-T3bN0 (age 16 or older in the UK, 18 or older elsewhere; ECOG performance status 0-1)
- Design
- International, multicentre, open-label, parallel-group, randomised phase 2/3 trial in five European countries (also registered as ISRCTN14240288). Participants with rectal adenocarcinoma up to 40 mm staged mrT1-T3bN0 were, in phase 2, randomly assigned 1:1:1 to long-course chemoradiotherapy-based organ preservation (LCCRT-OP; 50 Gy in 25 fractions with capecitabine), short-course radiotherapy-based organ preservation (SCRT-OP; 25 Gy in five fractions) or primary total mesorectal excision (TME). Phase 3 used a partially randomised patient-preference design: participants chose organ preservation or TME, and those choosing organ preservation were randomly assigned 1:1 to LCCRT-OP or SCRT-OP. Phase 2 primary endpoint: recruitment at months 12 and 24. Phase 3 primary endpoint: organ preservation 30 months after treatment initiation (absence of TME, stoma or local recurrence), which has not been reported. The 12-month report covers 426 participants recruited before 8 August 2023, of whom 409 formed the modified intention-to-treat population (163 allocated to LCCRT, 168 to SCRT, 78 to primary TME). The primary TME group comprises 36 participants randomised in phase 2 and 42 who chose surgery in phase 3 (registered, not randomised). The 12-month analysis uses a data snapshot of 2 June 2025; median follow-up of the cohort was 34 to 35 months, but only outcomes up to 12 months are analysed. The analysis is Bayesian, so results carry posterior probabilities rather than p values.
- Primary endpoint
- Organ preservation rate
- Arms
- Long-course chemoradiotherapy-based organ preservation (experimental, n = 163): Long-course chemoradiotherapy (50 Gy in 25 fractions with oral capecitabine 825 mg/m2 twice daily), response-adapted organ preservation
- Short-course radiotherapy-based organ preservation (experimental, n = 168): Short-course radiotherapy (25 Gy in five fractions), response-adapted organ preservation
- Primary total mesorectal excision (control, n = 78): Primary total mesorectal excision
- People
- Bach SP, senior author de Wilt JHW, STAR-TREC Collaborative
TME-free survivalHR 1.90 (95% CI 1.29–2.81)TME-free survivalHR 3.7 (95% CI 1.7–8.0)
Show the numbers
| Endpoint | Analysis | Long-course chemoradiotherapy-based organ preservation / Short-course radiotherapy-based organ preservation | Primary total mesorectal excision | Effect |
|---|---|---|---|---|
| TME-free survivalParticipants allocated to or choosing organ preservation in the 12-month modified intention-to-treat analysis: 331 (163 LCCRT-OP, 168 SCRT-OP), of whom 78 were randomised in phase 2 and 253 chose organ preservation in phase 3 and were then randomised between the two schedules. The full analysis population of 409 also includes 78 in the primary TME group.12-month TME-free survival (time from treatment initiation to death or total mesorectal excision) among participants allocated to or choosing organ preservation, from a 12-month analysis of implementation outcomes (not the phase 3 primary endpoint) | interimBach 2026 | 78.5% at 12 mo (72.4–85.1%) | — | HR 1.90 (95% CI 1.29–2.81)The hazard ratio is reported with a posterior probability of long-course chemoradiotherapy superiority above 99.5% (Bayesian analysis, no p value). The authors interpret the result as long-course chemoradiotherapy appearing more effective than short-course radiotherapy for organ preservation at 12 months, and state that longer follow-up is needed for the prespecified 30-month endpoint and for definitive functional and oncological outcomes. A post-hoc analysis by phase found a smaller effect in phase 3 than in phase 2 (HR 1.4, 95% CI 0.9 to 2.3), and the authors suggest the large phase 2 effect was probably due to chance in a small sample. |
| TME-free survivalPhase 2 participants (120 enrolled in phase 2); the number analysed in each arm is not given in the abstract or the main textTME-free survival in the planned interim analysis of unmasked phase 2 data (long-course chemoradiotherapy versus short-course radiotherapy) | interimBach 2026 | median 7.6 months | — | HR 3.7 (95% CI 1.7–8.0)The abstract reports 12-month median TME-free survival as not reached (95% CI not reached to not reached) with long-course chemoradiotherapy versus 7.6 months (95% CI 6.4 to not reached) with short-course radiotherapy, with a posterior probability of superiority above 99.5%. This analysis led the steering and data monitoring committees to recommend the expanded 12-month analysis. |
| Endpoint | Analysis | Long-course chemoradiotherapy-based organ preservation / Short-course radiotherapy-based organ preservation | Primary total mesorectal excision | Effect |
|---|---|---|---|---|
| TME-free survivalParticipants allocated to or choosing organ preservation in the 12-month modified intention-to-treat analysis: 331 (163 LCCRT-OP, 168 SCRT-OP), of whom 78 were randomised in phase 2 and 253 chose organ preservation in phase 3 and were then randomised between the two schedules. The full analysis population of 409 also includes 78 in the primary TME group.12-month TME-free survival (time from treatment initiation to death or total mesorectal excision) among participants allocated to or choosing organ preservation, from a 12-month analysis of implementation outcomes (not the phase 3 primary endpoint) | interimBach 2026 | 78.5% at 12 mo (72.4–85.1%) | — | HR 1.90 (95% CI 1.29–2.81)The hazard ratio is reported with a posterior probability of long-course chemoradiotherapy superiority above 99.5% (Bayesian analysis, no p value). The authors interpret the result as long-course chemoradiotherapy appearing more effective than short-course radiotherapy for organ preservation at 12 months, and state that longer follow-up is needed for the prespecified 30-month endpoint and for definitive functional and oncological outcomes. A post-hoc analysis by phase found a smaller effect in phase 3 than in phase 2 (HR 1.4, 95% CI 0.9 to 2.3), and the authors suggest the large phase 2 effect was probably due to chance in a small sample. |
| TME-free survivalPhase 2 participants (120 enrolled in phase 2); the number analysed in each arm is not given in the abstract or the main textTME-free survival in the planned interim analysis of unmasked phase 2 data (long-course chemoradiotherapy versus short-course radiotherapy) | interimBach 2026 | median 7.6 months | — | HR 3.7 (95% CI 1.7–8.0)The abstract reports 12-month median TME-free survival as not reached (95% CI not reached to not reached) with long-course chemoradiotherapy versus 7.6 months (95% CI 6.4 to not reached) with short-course radiotherapy, with a posterior probability of superiority above 99.5%. This analysis led the steering and data monitoring committees to recommend the expanded 12-month analysis. |
Data table
| Endpoint | HR | 95% CI |
|---|---|---|
| TME-free survival | 1.9 | 1.29–2.81 |
| TME-free survival | 3.7 | 1.7–8 |
- Short-course radiotherapy-based organ preservation (experimental)
Median-only curves assume a constant hazard (exponential) and fit plateaus, as seen with some immunotherapies, poorly.
Data table (modelled values)
| Months | Short-course radiotherapy-based organ preservation |
|---|---|
| 0 | 100.0% |
| 5 | 63.4% |
| 10 | 40.2% |
| 14 | 27.9% |
| 19 | 17.7% |
Appears in
Sources
Bach SP, Sebag-Montefiore D, Homer V, Gilbert A, Appelt A, Geh I, et al. Chemoradiotherapy versus short-course radiotherapy for response-adapted organ preservation in early-stage and intermediate-stage rectal cancer (STAR-TREC): 12-month results of an international, multicentre, open-label, parallel-group, randomised, phase 2/3 trial. Lancet Oncol. 2026;27(9):1120-1132.