- For rectal cancer, neoadjuvant radiotherapy (RT) at 5×5 Gy with surgery delayed to 4-8 weeks yields greater tumor regression compared with 25×2 Gy and/or shorter time to surgery.
Why this matters
- The best fractionation regimen and timing to surgery in the use of neoadjuvant radiotherapy for rectal cancer have not been established.
- These data are from the Stockholm III trial.
- Patients (n=840) were randomly allocated to:
- RT 5×5 Gy with surgery within 1 week (short-course RT [SRT]).
- 5×5 Gy with surgery after 4-8 weeks (SRT-delay).
- 2 Gy×25 with surgery after 4-8 weeks (long-course RT [LRT]-delay).
- Median follow-up, 5.7 years.
- This analysis focused on the correlation between tumor regression and OS.
- Funding: Swedish government, others.
- Pathological complete response (pCR):
- SRT: 0.3%
- SRT-delay: 10.4%
- LRT-delay: 2.2%.
- With pCR vs non-pCR:
- OS: HR, 0.51 (P=.046).
- Time to recurrence: HR, 0.27 (P=.027).
- 13% had missing pathology or nonevaluable slides.
- Long recruitment period could mean some changes in accuracy of preoperative staging.