Ozone Therapy in Chemotherapy-induced Peripheral Neuropathy: RCT (O3NPIQ)

Inclusion Criteria: * 1\. Adults \> = 18 years old. * 2\. Any kind of cancer in any stage, treated with any kind of chemotherapy, and life expectancy \> = 6 months. * 3\. Clinical diagnosis of painful chemotherapy-induced peripheral neuropathy, toxicity Grade 2 or higher according to the Common Toxicity Criteria for Adverse Events (CTCAE) from the National Cancer Institute of EEUU, v.5.0, for \> = 3 months and without the inclusion of new treatments for pain and/or neuropathy for \> = 1 month. * 4\. "Average pain" \> = 3/10 according to the Brief Pain Inventory-Short Form (BPI-SF) \> = 3 months beyond chemotherapy completion. * 5\. Pregnant women cannot participate in the clinical trial. * 6\. 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 the 14 days prior to the first ozone therapy session up to 14 days after the last one. * 7\. Patients who have signed and dated the study 's specific informed consent Exclusion Criteria: * 1\. Age \< 18 years old. * 2\. Pregnancy at the time of enrollment. * 3\. Women with childbearing potential who are unwilling to perform a pregnancy test and/or employ adequate contraception from the 14 days prior to the first ozone therapy session up to 14 days after the last one. * 4\. Clinical suspicion that peripheral neuropathy (compressive or diabetic neuropathy) in the same area pri…