OBJECTIVEArm lymphedema after surgery or radiation for breast cancer is common, causing pain and limitation of activities. Previous reports of hyperbaric oxygen (HBO) therapy for breast edema led us to consider the use of HBO therapy for arm lymphedema.METHODSTen healthy postmenopausal women (age 58 +/- 5.7 years) with persistent (9.4 years +/- 9.1 years) arm lymphedema following breast cancer surgery and radiation (n = 10) plus chemotherapy (n = 7) received 20 HBO treatments (90 minutes at 2.0 ATA five times a week for 4 weeks). End points included changes in upper extremity volume, platelet counts, plasma levels of vascular endothelial growth factor (VEGF), and lymph angiogenic-associated vascular endothelial growth factor-C (VEGF-C). Lymphedema volume (LV) was defined as the volume of the unaffected arm subtracted from the volume of the affected arm.RESULTSWe observed a 38% average reduction in hand lymphedema (-7.4 ml, 11.6 SD, range -30-+8 ml, p = 0.076, 95% confidence interval -15.7-0.9 ml) at the end of HBO, which was independent of changes in body weight. For those who benefited (n = 8), the reduction was persistent from the end of treatment to a final measurement an average of 14.2 months after the last HBO treatment. However, total LV did not change significantly. VEGF-C increased from baseline (p = 0.004) before treatment 20, suggesting HBO had begun to stimulate this growth factor.CONCLUSIONSFuture studies should explore the effects of a greater number of HBO treatments on lymphedema, with more patients.