Comparable results were reported in previousstudies on prostate cancer xenografts that were treated with similar treatmentconditions and assessed 24 h after treatment.4 This decrease in Ki-67 labelingalso supports the observation made by Lai et al,19 in breast cancer xenograftswhere tumors that were treated with a combination of USMB and radiation had slowertumor growth rates compared to untreated tumors in long term studies.19 This evidence concerns the gene MKI67 and breast carcinoma.