New enzyme-targeting radiosensitizer (KORTUC II) treatment for locally advanced or recurrent breast cancer.

Kochi oxydol radiation therapy for unresectable carcinomas II (KORTUC II) is currently the most widely used radiosensitizer in Japan. This sensitizer is a solution consisting of 0.83% sodium hyaluronate and 0.5% hydrogen peroxide. The mixture is injected intratumorally just before radiation therapy (RT) several times. KORTUC II has the effect of neutralizing antioxidant enzymes, while increasing the oxygen tension into the tumor tissue, and achieves marked local effects without notable adverse events. The present report describes cases in which KORTUC II was used to treat patients with locally advanced breast cancer (LABC) or recurrent breast cancer (LRBC). The present study included 30 patients with LABC (n=9) or LRBC (n=21) aimed at local control of tumors, who were followed up for ≥3 months after treatment. The irradiation dose and extent fields were determined by the attending physicians considering various patient factors, such as a performance status, prognosis and presence or absence of adjuvant therapy. The median irradiation dose was 60.4 Gy3.5 (43.6-76.1 Gy3.5) based on the calculation of equivalents of 2 Gy fractions, and the median total number of sensitizer injections was 5 (2-7) times. The median maximum tumor shrinkage was 97.0% and 15 patients (50%) were assessed to have achieved a clinical complete response. The proportion with loco-regional control at 1, 2 and 3 years was 100, 94.7 and 75.4%, respectively, and progression free survival after RT at 1 and 2 years was 59.0 and 24.1%, respectively. KORTUC II exhibited high rates of local tumor control for LABC and LRBC. KORTUC II is expected to be an inexpensive and promising RT method because it is safe and has an excellent radio-sensitizing effect.