Figure 3. Numbers of brain metastases per mouse at 4 weeks (top) or at 8 weeks (bottom) after tumor-cell injection.

Brain metastases were identified with a fluorescent stereomicroscope and the number of brain metastatic foci per mouse was counted. At 4 weeks, the group given whole-brain irradiation at 5 days after tumor-cell injection (prophylactic cranial irradiation [PCI]) had significantly fewer brain metastases per mouse than did the control group and the group given irradiation 2 days before tumor-cell injection (pre-irradiation). At 8 weeks, the group that was given whole-brain irradiation 5 days after tumor-cell injection (PCI group) had significantly fewer brain metastases per mouse than any of the other groups. Horizontal bars represent medians and lower/upper quartiles.