Hyperbaric oxygen alone or combined with 5-FU attenuates growth of DMBA-induced rat mammary tumors

We tested the hypothesis that hyperbaric oxygen (HBO) alone and with chemotherapy (5-FU) attenuates tumor growth of DMBA-induced tumors in rats. Six series were performed: (1) Controls (air and vehicle 0.9% NaCl i.p.), (2) 5-FU (0.2 mg/kg i.p.), (3) HBO (2 bar for 90 min and vehicle), (4) HBO and 5-FU, (5) HBO (11 days) and air (next 12 days), (6) HBO (23 days). All treatments were applied on days 1, 4, 7, 10 (Series 1–4), as well as on days 14, 17 and 23 (Series 5–6). Tumor diameter increased by 76.7 and 41.2% in untreated controls and in the 5-FU group, respectively, after 10 days. Tumor size fell by 17–24.2% in the HBO groups and by 35.5% when combined with 5-FU (P<0.05 compared to HBO). HBO treatment reduced the total number of blood vessels in the tumors. After completion of HBO treatment tumor size increased, but statistically insignificant, during the next 12 days.