INS and breast cancer: However, spurred by emerging observational evidence that physically active women had a lower risk of developing breast cancer, clinical investigators soon began conducting RCTs to examine the effect of exercise on biomarkers that associate with breast cancer prognosis (e.g., serum insulin, C-reactive protein, immune cell activity), doing so during and/or after initial adjuvant treatment (i.e., radiotherapy and/or chemotherapy) (5, 6).