RESUMEN
Background: Chronic pain secondary to treatment in cancer survivors without tumor evidence is not unusual. Its management often requires specific approaches that are different from those applied for cancer patients with advanced disease and short life expectancy. Some studies have described clinical benefit with ozone therapy (O3T) in the management of pain and side effects secondary to cancer treatment. Objective: We present our preliminary experience with O3T in the management of refractory pelvic pain syndromes secondary to cancer treatment. Design: Case series. Subjects and Methods: Six cancer patients (without tumor evidence) who had been treated previously with radiotherapy, chemotherapy, or endoscopic procedures and were suffering persistent or severe pelvic pain (median 14 months) received O3T using ozone-oxygen gas mixture insufflation as a complementary therapy in addition to their scheduled conventional treatment. Results: All cases, except one, showed clinically relevant pain improvement. Visual analog scale score with the standard treatment was 7.8 ± 2.1 before O3T, 4.3 ± 3.4 (p = 0.049) after one month, 3.3 ± 3.7 (p = 0.024) after two months, and 2.8 ± 3.8 (p = 0.020) after three months of O3T. The median value of "pain symptom" according to the U.S. National Cancer Institute Common Terminology Criteria for Adverse Events v. 5.0 showed a decrease from 3 (range: 2-3) to 1 (range: 0-3) (p = 0.046). Conclusions: Following unsuccessful conventional treatments, O3T provided significant benefit in our patients with refractory pelvic pain secondary to cancer treatment. These results merit further evaluation in blinded, randomized clinical trials.