XVI.4
Step 4: Retreatment Options
If the first FMT brings no response, several paths remain — switching donors, stronger induction, longer consolidation, or an adjuvant therapy — each matched to the cause of non-response.
| Retreatment option | Indication / timing / notes |
|---|---|
| Donor change | Indicated if Phase 0 data suggests suboptimal compatibility. Select donor with highest predicted complementarity to recipient dysbiosis profile. Most evidence-supported retreatment strategy. |
| Intensified induction | Additional colonoscopic FMT or high-dose capsule loading (3–5 consecutive days). Indicated in engraftment failure without clear donor-incompatibility signal. Can be combined with donor change. |
| Extended consolidation | Extend Phase 2 by 4–8 weeks before declaring non-response in chronic inflammatory conditions. Evidence supports duration-dependent response in UC and Crohn's. |
| Protocol pause + exposome reset | 2–4 week pause with intensive exposome correction before re-starting. Indicated when Category C factors identified. Allows ecological stabilization before re-inoculation. |
| Combination with adjunct therapy | FMT + biologic (IBD), FMT + dietary intervention (metabolic), FMT + psychological intervention (IBS). Evidence for combination emerging; discuss with clinical team. |
| Compassionate repeat cycles | For partial but genuine responders: additional protocol cycles after 3–6 month rest period. Decision based on quality-of-life benefit, biomarker trends, and patient preference. |
Table 22 – Retreatment options by non-response scenario # Structured retreatment framework: donor change, protocol modification, and dose escalation options by clinical context.