Fifty patients (N=50) with histologically confirmed invasive ductal carcinoma (IDC) were analyzed on MRI (1.5 T Magnetom Avanto,
Siemens Medical Solutions,
Erlangen,
Germany; Standardized diagnostic protocol: T2W STIR,
T2W-TSE,
T1W-TSE,
DWI,
dynamic 3D-FLASH enhanced; Contrast medium: Gd-DTPA,
Magnevist,
Bayer Schering Pharma,
Berlin,
Germany):
- Before the initial course of NACT
- After the 2nd cycle of NACT
According to the predefined endpoints:
1.) RECIST – Response evaluation criteria in solid tumors,
version 1.1 (RECIST 1.1): the unidimensional measuring tool,
defining and further evaluating the largest tumor diameter (cm) or the sum of the target lesions largest diameters (cm),
with the follow-up response evaluated according to the response categories: CR,
PR,
stable disease (SD) and progression of the disease (PD) [1,
6].
2.) Apparent diffusion coefficient (ADC) – DWI and ADC maps were acquired using b-values of 0 and 800 mm2/s.
ADC maps were calculated / created using image processing software – DICOM viewer OsiriX with plug-ins (OsiriX,
Pixmeo,
Geneva,
Switzerland).
ADC values were calculated according to the following model:
ADC = 1n [(s0 / s1)] / (b1 - b0)
ln – the natural log;
b0 = 0 mm2/s;
b1 = 800 mm2/s;
s0,
s1 – signal intensities of the lesion per each b-value [4].
The selected MRI parameters (RECIST and ADC) were tested against the histopathological findings.
Based on the histopathological findings,
the two subgroups were created [6,
7]: a.) Responders (R,
N1=25; patients with pathologic complete response (pCR) and near-pCR) b.) Nonresponders (NR,
N2=25)
The nonparametric two-tailed Mann-Whitney U test was performed for the comparison of R and NR [9].
The P value of 0.05 or less,
or when possible 0.01 or 0.001,
was considered significant.
The Spearman’s rank correlation coefficient was also calculated [9].
Wilcoxon’s test was chosen to test the differences within the subgroup R or NR [9].