Gut Microbiome Profiles in Patients With Chemotherapy-induced Neuropathy in the RCT OzoParQT (NCT06706544).

Chemotherapy-induced peripheral neuropathy (CIPN) is a common and debilitating side effect of chemotherapy (CT), often requiring dose reductions or treatment interruptions, which can compromise efficacy of the planned CT (limiting its efficacy). Additionally, CIPN usually decreases patients' quality of life. Unfortunately, effective treatments for CIPN are limited. Emerging evidence suggests potential benefits of rectal ozone therapy and points to a possible role of the gut microbiome in CIPN development and treatment response. This observational study, ancillary to the randomized clinical trial (RCT) OzoParQT (NCT06706544), investigates the relationship between gut microbiome composition and CIPN severity in patients receiving rectal ozone therapy. Primary Objectives: To evaluate if gut microbiome profiles differ between patients: 1. with and without symptomatic improvement of CIPN. 2. receiving rectal ozone therapy and those receiving placebo. Secondary Objectives: To evaluate the relationship between gut microbiome composition and: 1. Health-related quality of life, 2. Anxiety and depression, 3. Biochemical markers of oxidative stress and inflammation. Main Trial Endpoints. Changes from baseline at the end of ozone therapy (week 16) in: * Gut microbiome profile * Patient-reported numbness and tingling * Neuropathy severity (QLQ-CIPN20 scale) * Paresthesia toxicity grade (CTCAE v.5.0) Secondary Trial Endpoints. Changes from baseline at the end of ozone therapy (week 16) in: * Patient-reported quality of life (EQ-5D-5L questionnaire) * Quality of life (QLQ-C30 questionnaire) * Anxiety and depression levels (HADS questionnaire) * Biochemical markers of oxidative stress * Biochemical markers of inflammation Trial Design: This observational study will analyze data from patients enrolled in the randomized, triple-blind, placebo-controlled OzoParQT clinical trial (NCT06706544). Trial Population in the OzoParQT trial (NCT06706544): Adults (≥18 years) with any tumor type, experiencing CIPN-related paresthesias (numbness and/or tingling), with a toxicity grade ≥ 2 according to the Common Terminology Criteria for Adverse Events (CTCAE v.5.0) for ≥ 3 months. Intervention in the OzoParQT trial (NCT06706544). All patients will receive standard care for their CIPN symptoms plus 40 sessions of rectal insufflation of an O3/O2 gas mixture over 16 weeks: * Ozone group: O3/O2 concentration increasing from 10 to 30 µg/mL * Control-placebo group: O2 only (0 µg/mL O3) Study Duration: Each patient will participate in this study (OzoParQTmicrob) for 16 weeks, concurrent with the ozone therapy intervention. The total planned project duration is 60 months.

Sex

All

Minimum age

18 Years

Inclusion Criteria:

* 0\. Patients who agree to participate in the randomized clinical trial OzoParQT, and who also agree to participate in this study of gut microbiota by providing stool samples.
* 1\. Adults \> = 18 years old.
* 2\. Previous treatment with any chemotherapy because of any tumor.
* 3\. Clinical diagnosis of paresthesia (numbness, tingling) secondary to CIPN, with toxicity Grade \> = 2 (according to the Common Toxicity Criteria for Adverse Events (CTCAE) from the National Cancer Institute of EEUU, v.5.0) for \> = 3 months.
* 4\. Without neurotoxic chemotherapy \> = 3 months.
* 5\. Cancer disease is stable or in remission.
* 6\. Life expectancy \> = 6 months.
* 7\. Before enrollment, women of childbearing potential should obtain a negative result in the serum or urine pregnancy test at the screening visit and accept the use of appropriate contraceptive methods at least from 14 days before the first ozone therapy session up to 14 days after the last one.
* 8\. To sign and date the specific informed consent of both studies (OzoParQT and OzoParQTmicrob)

Exclusion Criteria:

* 1\. Age \< 18 years.
* 2\. A woman who is lactating, pregnant, suspected of being pregnant, or a woman of childbearing potential who does not use adequate contraceptive methods.
* 3\. Suspected symptoms are due to diabetic or compressive neuropathy.
* 4\. Severe psychiatric disorders.
* 5\. Inability to complete the quality of life questionnaires.
* 6\. Elevation above 5 times the maximum limit of normal creatinine.
* 7\. Patient who is hemodynamic or clinically unstable or who requires urgent or short-term interventional measures.
* 8\. Neoplasia in progression requiring recent initiation of systemic treatment or maintenance with neurotoxic chemotherapy.
* 9\. Life expectancy (for any reason) \< 6 months.
* 10\. Known allergy to ozone, known glucose 6 phosphate dehydrogenase (G6PD) deficiency, or hemochromatosis.
* 11\. Contraindications or impossibility for rectal ozone treatment or to attend regularly to the treatment.
* 12\. Not meeting each and every one of the inclusion criteria

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