Fig. 6

Intratumor heterogeneity in the effect of low dose bevacizumab treatment. a-b, K ^trans image of a representative untreated A-07 tumor (a), and image illustrating how the tumor was divided in 5 concentric circular ROIs (b). The circular ROIs are bounded by lines drawn at distances of nR/5 from the tumor center, where R is tumor radius and n is ROI number. Color bar shows K ^trans scale, scale bars are 2 mm. c-d, K ^trans in 5 concentric circular ROIs before treatment, and in untreated and bevacizumab-treated tumors 7 days after the treatment started. The graphs refer to A-07 (c) and R-18 (d) tumors. Symbols, means of 4–9 tumors, bars, SEM. Statistical comparisons of the data were carried out by the Student’s t test or the Mann–Whitney rank sum test. After the treatment period (day 7), differences in K ^trans values between untreated and bevacizumab-treated A-07 tumors were not significant in ROI 1–3 (P > 0.05), were borderline significant in ROI 4 (P = 0.063), and were significant in ROI 5 (P = 0.016). For R-18 tumors, significant differences between untreated and bevacizumab-treated tumors were not found in any ROI (P > 0.05)