Thesis

192 Part II Chapter 8 Figure 2. Bland-Altman plot visualizing a strong relation between baseline SUVcut-off and follow-up, no heteroskedasticity. For the total of 37 PET-CT-scans, the individual SUVcut-off ranged from 3.62-10.62 g/ mL (median: 7.98 g/mL), in accordance with our previous study a range larger than the predefined median ± 10% [4, 12]. Pairwise, these individual SUVcut-offs of followup scans were not significantly different from baseline, as shown in Table 3. Also for the subcohorts of denosumab (n=8) and non-denosumab (n=7), the (distribution of) SUVcut-offs for healthy bone did not change after treatment compared to baseline, p=0.237 and p=0.575 (Wilcoxon), respectively. As in our previous study individual SUV-cut offs varied > 10% ranging from 3.62-10.62 g/mL (median: 7.98 g/mL), therefore individualized cut-offs were also used in this follow-up study [4, 12]. Individual SUVcut-offs of follow-up scans for healthy bone were not significantly different from baseline, Table 3, not for denosumab (n=8) user nor for non-denosumab (n=7) users, p=0.237 and p=0.575 for FU vs BL respectively. The intrapatient ICC between baseline and second Na[18F]F PET-CT SUVcut-off was 0.856 (p=0.001). The intrapatient repeatability of SUVcut-off for healthy bone for all scans was substantial (ICC=0.615; p=0.006), Bland-Altman mean difference -0.51 g/mL, levels of agreement -3.31 to +2.29 g/mL (Figure 2), measured in 15 patients (37 scans) between baseline and all follow-up scans.

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