Organ preservation in rectal cancer trades the morbidity of total mesorectal excision for the uncertainty of watch-and-wait. STAR-TREC asked which radiotherapy schedule gets more patients there.
This international phase 2/3 trial across 37 sites in five European countries enrolled patients with rectal adenocarcinoma up to 40 mm, staged mrT1 to T3bN0, with performance status 0 to 1. Phase 2 randomised three ways — long-course chemoradiotherapy at 50 Gy in 25 fractions with capecitabine, short-course radiotherapy at 25 Gy in five fractions, or primary surgery. Phase 3 used a patient-preference design: patients chose organ preservation or surgery, and those choosing preservation were randomised between the two schedules.
An interim analysis of unmasked phase 2 data showed an early advantage for long-course, and the expanded 12-month analysis of 409 patients confirmed it. Among those opting for organ preservation, 12-month survival free of total mesorectal excision was 78.5% (95% CI 72.4 to 85.1) with long-course chemoradiotherapy and 60.6% (53.6 to 68.4) with short-course, hazard ratio 1.90 (95% CI 1.29 to 2.81).
Serious adverse events were lowest in both radiotherapy arms and highest with primary surgery: gastrointestinal grade 3-4 events in 2% with long-course, 4% with short-course and 8% with surgery. One patient allocated to primary surgery died after an anastomotic leak.
These are 12-month implementation results, not the prespecified 30-month organ-preservation endpoint, and the difference between the schedules could narrow as salvage surgery accrues. What can be said now is that if organ preservation is the goal, long-course chemoradiotherapy is the schedule that gets more patients there in the first year.
- Where organ preservation is the intent in early or intermediate rectal cancer, choose long-course chemoradiotherapy over short-course radiotherapy
- Quote the 12-month figures honestly: about 79% versus 61% avoid total mesorectal excision at one year
- Note that serious adverse events were lowest in both radiotherapy arms and highest after primary surgery
- Wait for the 30-month endpoint before treating the difference between schedules as final
- Organ preservation requires a reliable surveillance programme; it is not a way to avoid follow-up
The statistics, in plain English
A hazard ratio of 1.90 here favours long-course chemoradiotherapy because the event being counted is progression to surgery, so a higher ratio in the short-course arm means more patients came to resection. Read the direction of the endpoint before the direction of the ratio. The bigger caveat is design: phase 3 used a patient-preference structure in which patients chose organ preservation or surgery and only then were randomised between schedules, so the surgery comparison is not randomised and cannot support causal claims. The schedule comparison is randomised and can. And 12 months is an implementation readout, not the prespecified 30-month endpoint.
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