Letter: Early Inflammatory Benefit Is Not Yet Equivalent to Durable Surgical Advantage After Colectomy in Colonic Crohn's Disease. Authors' Reply

We thank Dr Li [1] for the careful reading of RESECOL [2] and for raising these points. Regarding confounding by indication, we agree that this is the main methodological challenge in any retrospective surgical comparison. Surgical indication was included in the propensity score model, and inverse probability of treatment weighting (IPTW) was applied precisely to correct for the differences between groups, including more medically refractory disease in the subtotal colectomy (STC) arm and more fistulising disease in the segmental colectomy (SC) arm. We believe the IPTW-adjusted estimates are therefore more valid than unadjusted comparisons, even if residual unmeasured confounding cannot be fully excluded. On disease extent, we agree that this is clinically relevant. In our cohort, L2 disease accounted for 42% of SC and 49% of, with L3 representing the remaining 58% and 51%, respectively. However, stratified analyses by extent are not feasible here without a serious loss of statistical power. Dividing the STC group by L2 vs. L3 leaves approximately 30 patients per subgroup, which is too small for any meaningful adjusted comparison. The same applies to stratification by surgical indication: With five indications recorded across two procedure groups, subgroup analyses would be severely underpowered. Regarding resection margins, RESECOL included a sensitivity analysis excluding patients with affected margins, and the results were consistent with the primary analysis. Margin status, therefore, does not appear to materially change the observed associations. Finally, we acknowledge that the protective effect of SC for endoscopic recurrence was time-dependent, remaining significant at 12 months but not at later timepoints. The median follow-up in our cohort was six years, and the loss of statistical power in the later parts of the survival curves is an inherent limitation of long-term retrospective studies. Whether the early endoscopic advantage translates into durable separation over longer follow-up remains an open question for future prospective studies. We agree with Dr Li that RESECOL should be read as hypothesis-generating. Larger prospective studies with standardised endoscopic monitoring will be needed to confirm whether the early inflammatory advantage of SC represents a durable surgical benefit. José Luis Rueda García: conceptualization, writing – original draft. Cristina Suárez-Ferrer: conceptualization, writing – review and editing. Yamile Zabana: conceptualization, writing – review and editing. The authors' declarations of personal and financial interests are unchanged from those in the original article [2]. This article is linked to Rueda García et al. papers. To view these articles, visit https://doi.org/10.1111/apt.70608 and https://doi.org/10.1111/apt.70700. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.