The value of diffusion kurtosis imaging in assessing pathological complete response to neoadjuvant chemoradiation therapy in rectal cancer: a comparison with conventional diffusion-weighted imaging

Abstract

ObjectivesThe aim of this study is to comprehensively evaluate the advantage of diffusion kurtosis imaging (DKI) in distinguishing pathological complete response (pCR) from non-pCR patients with locally advanced rectal cancer (LARC) after neoadjuvant chemoradiation therapy (CRT) in comparison to conventional diffusion-weighted imaging (DWI).Material and MethodsFifty-six consecutive patients diagnosed with LARC were prospectively enrolled and underwent pre- and post-CRT MRI on a 3.0 T MRI scanner. Apparent diffusion coefficient (ADC), mean diffusion (MD) and mean kurtosis (MK) values of the tumor were measured in pre- and post-CRT phases and then compared to histopathologic findings after total mesorectal excision (TME). Both Mann-Whitney U-test and Kruskal-Wallis test were used as statistical methods. Diagnostic performance was determined using receiver operating characteristic (ROC) curve analysis.ResultsFor a total of 56 rectal lesions (pCR, n = 14; non-pCR, n = 42), the MKpre and MKpost values were much lower for the pCR patients (mean±SD, 0.72±0.09 and 0.56±0.06, respectively) than those for the non-pCR patients (0.89±0.11 and 0.68±0.08, respectively) (p < 0.001). The ADCpost and the change ratio of apparent diffusion coefficient (ADCratio) values was significantly higher for the pCR patients (mean±SD, 1.31±0.13 and 0.64±0.34, respectively) than for the non-pCR patients (1.12±0.16 and 0.33±0.27, respectively) (p < 0.001 and p = 0.001, respectively). In addition, the MDpost and the change ratio of mean diffusion (MDratio) (2.45±0.33 vs. 1.95±0.30, p < 0.001; 0.80±0.43 vs. 0.35±0.32, p < 0.001, respectively) also increased, whereas the ADCpre, MDpre and the change ratio of mean kurtosis (MKratio) of the pCR (0.82±0.11, 1.40±0.21, and 0.23±0.010, respectively) exhibited a neglectable difference with that of the non-pCR (p = 0.332, 0.269, and 0.678, respectively). The MKpost showed relatively high sensitivity (92.9%) and high specificity (83.3%) in comparison to other image indices. The area under the receiver operating characteristic curve (AUROC) that is available for the assessment of pCR using MKpost (0.908, cutoff value = 0.6196) were larger than other parameters and the overall accuracy of MKpost (85.7%) was the highest.ConclusionsBoth DKI and conventional DWI hold great potential in predicting treatment response to neoadjuvant chemoradiation therapy in rectal cancer. The DKI parameters, especially MKpost, showed a higher specificity than conventional DWI in assessing pCR and non-pCR in patients with LARC, but the pre-CRT ADC and MD are unreliable.

Quantitative intravoxel incoherent motion parameters derived from whole‐tumor volume for assessing pathological complete response to neoadjuvant chemotherapy in locally advanced rectal cancer

“…In addition, this study found that pre‐ADC and pre‐D values significantly increased in the pCR group compared with post‐ADC and post‐D values. It was different from several previous studies that obtained increased ADC values in the pCR and non‐pCR groups . Furthermore, several studies showed that posttreatment ADC and D values could help distinguish pCR from non‐pCR in patients with LARC.…”

“…Perhaps the necrotic area in the tumor could decrease the movement of water molecules and also inhibit the delivery of therapy due to lack of vascularization. Conversely, several studies reported that pretreatment ADC and D values were not associated with the pCR status. These differences might be because of the variations in the MRI technique and the difference in measurement methodology such as ROI selection.…”

“…Contouring lesions on a representative section of rectal tumor was the most common and convenient method. However, the distribution of signal intensity in rectal cancer was heterogeneous, and a single section of tumor may not represent the information on tumor heterogeneity . Moreover, the selection of section and the position of ROIs highly depended on the subjective judgment of different observers.…”

“…Apparent diffusion coefficient (ADC), the quantitative parameter of DWI, has been used as an imaging marker to evaluate rectal tumor response to therapy . Several recent studies demonstrated the potential of ADC in distinguishing pCR from non‐pCR, but the results remained inconsistent . This is possibly because the ADC value could reflect the rate of diffusion in cellular tissues but failed to distinguish the perfusion effects from true tissue diffusion, thereby introducing the signal attenuation of imaging .…”

“…2 Several recent studies demonstrated the potential of ADC in distinguishing pCR from non-pCR, but the results remained inconsistent. 2,[19][20][21][22][23][24][25][26] This is possibly because the ADC value could reflect the rate of diffusion in cellular tissues but failed to distinguish the perfusion effects from true tissue diffusion, thereby introducing the signal attenuation of imaging. 27,28 Intravoxel incoherent motion (IVIM) model, which could estimate tissue perfusion and diffusion components individually using multi-b-values, was introduced to overcome this limitation.…”