Oxidative stress of red blood cells during Bacillus Calmette-Guerin intravesical instillations

Although Bacillus Calmette-Guerin (BCG) intravesical instillation is widely accepted as a very effective modality in treating bladder carcinoma in situ, and in preventing superficial bladder cancer recurrence, its mechanism of action is not yet fully understood. The antitumor effects of BCG are mostly related to local immunological events but a systemic activation of the immune system cannot be excluded. The objective of the present study was to estimate the systemic production of oxidants during intravesical BCG treatment. Systemic production of oxidants was estimated by assessing the red blood cells (RBC) oxidative stress in twelve patients undergoing BCG immunotherapy for bladder carcinoma in situ. RBC oxidative stress induced by peroxynitrite was determined by luminol-enhanced chemiluminescence. During the treatment period, the RBC oxidative stress revealed a biphasic curve of changes: after an initial 5-fold increase, it dropped to pretreatment levels following the 4th instillation. Intravesical BCG administration induced systemic production of oxygen free radicals that may reflect a systemic activation of the immune system.