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Extending nCRT-to-Surgery Interval to 12 Weeks Shows No Benefit in Rectal Cancer
In a randomized controlled trial of 124 patients with locally advanced rectal cancer, extending the interval between neoadjuvant chemoradiotherapy and surgery from 8 to 12 weeks produced virtually identical pathological complete response rates (14.8% vs 14.5%, p = 0.904) and comparable three-year survival outcomes. Neither tumor downstaging nor disease-free or overall survival improved with the longer waiting period, and a numerically higher rate of anastomotic leakage was observed in the 12-week group.
What Was Studied
This trial investigated whether prolonging the recovery interval between completion of neoadjuvant chemoradiotherapy (nCRT) and total mesorectal excision (TME) improves pathological tumor response in locally advanced rectal cancer. The primary endpoint was pathological complete response (pCR), defined as Dworak grade 4, with secondary endpoints encompassing surgical quality, postoperative complications, disease-free survival, overall survival, and recurrence patterns.
How It Was Studied
This was a randomized controlled trial enrolling adult patients with histologically confirmed, MRI-staged stage II–III rectal adenocarcinoma located within 12 cm of the anal verge. A total of 124 patients were analyzed after randomization to surgery at either 8 weeks (n = 61) or 12 weeks (n = 63) following completion of long-course nCRT consisting of 50 Gy with concurrent 5-fluorouracil. In practice, actual median times to surgery exceeded the protocol targets, recorded at 10.3 weeks and 13.3 weeks in the respective groups, meaning the real-world interval difference was approximately three weeks rather than the intended four.
What Was Observed
- No difference in pathological complete response: pCR rates were nearly identical between the 12-week and 8-week groups (14.8% vs 14.5%, p = 0.904), indicating that waiting longer did not meaningfully increase the proportion of patients achieving complete tumor eradication at surgery.
- Comparable oncological outcomes at three years: Three-year overall survival was 76.3% in the 8-week group versus 80.0% in the 12-week group — a non-significant difference (p = 0.657). Disease-free survival was similarly equivalent at 62.9% versus 62.2% (p = 0.838), with no statistically meaningful divergence in recurrence patterns.
- Higher anastomotic leakage in the longer-interval group: Anastomotic leakage occurred in 15.9% of patients in the 12-week group compared with 4.9% in the 8-week group — a numerically important difference, though statistical significance was not formally reported for this comparison. This signal warrants attention given its potential clinical impact.
- Differential adjuvant chemotherapy use: Adjuvant chemotherapy was administered significantly more often in the 8-week group than in the 12-week group (61.7% vs 39.7%, p = 0.015), a difference that may reflect oncologist decision-making based on residual disease burden and could complicate interpretation of the survival outcomes.
Why This Matters
The optimal timing of surgery after nCRT has been an unresolved question in the management of locally advanced rectal cancer, with the assumption that longer intervals allow greater tumor regression. This trial provides direct randomized evidence challenging that assumption, finding no improvement in tumor response, nodal downstaging, circumferential resection margin status, or TME quality with the extended interval. The authors also note that these findings should be interpreted within the context of evolving total neoadjuvant therapy (TNT) strategies, which may reframe how and when surgical timing is considered in future protocols.
How to Read This Result
Given the moderate sample size (N = 124), the trial may have been underpowered to detect modest but clinically meaningful differences, and the neutral findings should be interpreted with appropriate caution rather than as definitive evidence of equivalence.
Limitations
The relatively small sample size of 124 patients limits statistical power and the precision of effect estimates. Actual surgery times exceeded protocol targets in both arms, narrowing the real-world interval difference to roughly three weeks and potentially diluting any true biological effect. Additionally, the evolving adoption of total neoadjuvant therapy frameworks may limit the generalizability of these findings to current and future treatment paradigms.