Radiotherapy With Hydrogen Peroxide-Soaked Gauze for Unresectable Breast Cancer

A hydrogen peroxide (H₂O₂)-soaked gauze has been used in combination with radiotherapy in anticipation of sensitizing tumors exposed to the skin surface. Although used empirically in the clinic, the method is rarely reported in the literature, making its efficacy and tolerability unclear. Here, we report a case of primary metastatic breast cancer whose primary tumor was treated with palliative radiotherapy using an H₂O₂-soaked gauze. The primary tumor in the right breast regrew after treatment with palbociclib plus letrozole followed by fulvestrant and denosumab. The tumor was exposed to the skin surface, causing exudation, bleeding, pain, and difficulty in raising the right upper limb. Radiotherapy (51 Gy in 17 fractions) using the H₂O₂-soaked gauze resolved the patient's symptoms and the tumor showed macroscopic complete remission at three months post-treatment. This case indicates that radiotherapy with an H₂O₂-soaked gauze is an effective and tolerable palliative treatment for superficially exposed tumors. This non-invasive and inexpensive method of radiosensitization warrants validation and optimization in a prospective setting.