Modulating the Gut Microbiota via Rectal Ozone Insufflation in Gynecological Cancer Patients with Radiotherapy/Chemotherapy-Induced Pelvic Toxicity: A Proposed Clinical Study Protocol

Background: Chronic pelvic toxicity induced by radiotherapy and/or chemotherapy (R/CIPT) is a debilitating sequela in gynecological cancer survivors, often refractory to conventional treatments and potentially linked to gut microbiota dysbiosis. Ozone therapy (OT), particularly rectal insufflation, demonstrates anti-inflammatory and redox-modulating effects through hormetic mechanisms (Nrf2 activation/NF-κB inhibition). We hypothesize that its clinical benefit is mediated, in part, by restoring gut microbial homeostasis. Objective: This manuscript proposes a clinical study to evaluate the impact of rectal OT on the gut microbiota of patients with gynecological cancers and chronic R/CIPT. Proposed Methods: A prospective, observational study of 38 patients is outlined: 19 with CTCAE v5.0 Grade ≥2 chronic R/CIPT receiving compassionate rectal OT (~40 sessions over 4 months), and 19 matched controls without toxicity. Stool samples for 16S rRNA sequencing will be collected from the OT group pre- and post-intervention and once from controls. Primary endpoints are changes in microbiota composition/diversity and pelvic toxicity scores (CTCAE v5.0, EORTC QLQ-CX24). Secondary endpoints include quality of life (EORTC QLQ-C30, EQ-5D-5L), anxiety/depression (HADS), and serum inflammatory/oxidative stress biomarker analysis. Anticipated Results and Conclusion: This will be the first study to prospectively investigate whether rectal OT’s effect correlates with a beneficial shift in the gut microbiota, specifically an increase in commensals (e.g., short-chain fatty acids producers) and a decrease in pathobionts. If successful, OT could be assessed as a novel, microbiota-targeting intervention for R/CIPT. The findings from this pilot study will provide the necessary groundwork for a future randomized controlled trial to definitively establish causality and efficacy.