Abstract
Physical activity offers a paradoxical hormetic effect and a health benefit to cancer survivors; however, the biochemical mechanisms have not been entirely elucidated. Despite the well-documented evidence implicating oxidative stress in breast cancer, the association between health benefits and redox status has not been investigated in survivors who participate in dragon boating. The present study investigated the plasmatic systemic oxidative status (SOS) in breast cancer survivors involved in two distinct physical training exercises. A total of 75 breast cancer survivors were allocated to one of three groups: Control (resting), dragon boat racing and walking group; the latter is a type of aerobic conditioning exercise often advised to cancer patients. Various biochemical oxidative stress markers were examined, including oxidant status (hydroperoxide levels, lipid oxidation) and antioxidant status (enzymatic activities of superoxide dismutase and glutathione peroxidase, reduced glutathione levels and antioxidant capability). In addition, the individual DNA fragmentation and DNA repair capability of nucleotide excision repair (NER) systems were examined by comet assays. According to the results, all patients exhibited high levels of oxidative stress. Physical activity maintained this oxidative stress condition but simultaneously had a positive influence on the antioxidant component of the SOS, particularly in the dragon boat racing group. DNA fragmentation, according to the levels of single- and double-strand breaks, were within the normal range in the two survivor groups that were involved in training activities. Radiation-induced damage was not completely recognised or repaired by NER systems in any of the patients, probably leading to radiosensitivity and/or susceptibility of patients to cancer. These findings suggest that physical activity, particularly dragon boat racing, that modulates SOS and DNA repair capability could represent a strategy for enhancing the quality of life and improving the long-term health benefits for breast cancer survivors.