Thirty-seven patients fulfilled the inclusion criteria. The histopathological diagnoses were NB in 16 cases (including one patient with bilateral NB), GNB in 11 cases, and GN in 10 cases. There were 38 measurable lesions. Nineteen patients underwent surgical resection without preoperative chemotherapy while the remaining 18 patients received neoadjuvant chemotherapy prior to the operation.
Mean patient age at operation was 5 ± 4 years (range 0 – 16). Median time period between surgical resection and MRI was 18 days (interquartile range (IQR): 27; range 1 – 98). Further characteristics are displayed in Table 1.
Intra- and inter-reader variability
ICC for inter-reader variability ranged from 0.983 (axial T1w precontrast) to 0.995 (axial DWI). ICC for intra-reader variability of reader 1 ranged from 0.985 (axial T1w precontrast) to 0.993 (3D T1w postcontrast). ICC for intra-reader variability of reader 2 ranged from 0.988 (axial T1w precontrast) to 0.996 (3D T1w postcontrast). Fig. 1 shows an example of axial and 3D MRI measurement (Fig. 1). Bland-Altman plots for the comparison of reader 1 and 2 are displayed in Fig. 2a and b (Fig. 2a and b).
Comparison of histopathology and MRI diameters
Due to the high inter-reader agreement of both readers, only the results of reader 1 are displayed in the following. Data of both readers is displayed in Tables 2 – 4. Median histopathological tumor size of the resected specimens was 5.8 cm (IQR: 4.2 cm; range 3.2 – 16.3 cm). The comparison of the maximum axial diameters revealed a significant difference between measurements of the resected specimens and all applied MRI sequences. Median axial T1w precontrast tumor size was 4.7 cm (median difference: -1.4 cm; p<0.001). Median axial T1w postcontrast tumor size was 4.9 cm (median difference: -1.0 cm; p<0.001). Median axial T2w lesion size was 4.7 cm (median difference: -1.0 cm; p<0.001). Median axial DWI tumor size resulted in 5.5 cm (median difference: -1.3 cm; p<0.001).
There was no significant difference between 3D MRI based lesion size measurements and the resected specimens regardless of the applied sequence. Median 3D T1w precontrast tumor size was 5.4 cm with a median difference of -0.3 cm (p=0.262). Median 3D T1w postcontrast tumor size was 5.5 cm (median difference: -0.1cm; p=0.739). Median 3D T2w tumor size resulted in 5.4 cm (median difference: -0.3 cm; p=0.379). Median 3D DWI based tumor size was 6.5 cm (median difference: -0.2 cm; p=0.159). Further details for reader 1 and 2 are displayed in Table 2.
There was almost perfect Pearson correlation (>0.85) between histopathology measurements of the resected specimens and MRI measurements regardless of the sequence (Table 3).
The Bland-Altman assessment provided a systematic underestimation for all sequences and for both readers. Lowest mean difference was found for reader 1 in 3D T1w postcontrast (-0.1 cm) and for reader 2 in 3D T2w TSE (-0.1 cm). Bland-Altman plots for reader 1 are displayed in Fig. 3a and b (Fig. 3a and b).
Influence of neoadjuvant therapy
Eighteen patients with 19 lesions (NB: n=11; GNB: n=8) received neoadjuvant chemotherapy prior to surgery. Nineteen patients (NB: n=6; GNB: n=3; GN: n=10) underwent gross total resection without preoperative chemotherapy. Median tumor size after neoadjuvant chemotherapy according to the histopathology report was 5.8 cm (IQR: 3.8 cm) vs. 5.8 cm (IQR: 5.2 cm) without chemotherapy (p=0.817).
In the group of patients with neoadjuvant chemotherapy, 3D T1w precontrast measurements resulted in a median of 5.2 cm with a median difference of -0.3 cm (p=0.224). Three-dimensional T1w postcontrast measurements achieved slightly higher results with a median of 5.3 cm (median difference: -0.1 cm; p=0.369). Three-dimensional T2w measurements had similar results with a median of 5.1 cm (median difference: -0.4 cm; p=0.101). There was also no significant difference in 3D DWI tumor margins with a median diameter of 5.2 cm (median difference: -0.5 cm; p=0.100). Similar to the overall assessment, all axial measurements were significantly different from the resected specimens (Table 4).
In patients without neoadjuvant therapy the comparison of lesion size between the resected specimens and MRI measurements showed no significant difference in 3D measurements whereas all axial measurements (except axial DWI for reader 2) were significantly different. Further details are displayed in Table 4.