Abstract
To investigate the usefulness of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in discriminating the pathological complete response (pCR) to neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer (LARC), 42 patients underwent preoperative IVIM-DWI before (pre-nCRT) and after nCRT (post-nCRT). The values of pre-nCRT and post-nCRT IVIM-DWI parameters (ADC, D, D* and f), together with the percentage changes (∆% parametric value) induced by nCRT, were compared between the pCR (tumour regression grade [TRG] 4) and non-pCR (TRG 0, 1, 2 or 3) groups and between the GR (TRG 3 or 4) and PR (TRG 0, 1 or 2) groups based on the Dworak TRG system. After nCRT, the ADC and D values for LARC increased significantly (all P < 0.05). The TRG score revealed a positive correlation with pref (r = 0.357, P = 0.020), postD (r = 0.551, P < 0.001) and Δ%D (r = 0.605, P < 0.001). The pCR group (n = 10) had higher preD*, pref, postD, ∆%ADC and ∆%D values than the non-pCR group (n = 32) (all P < 0.05). The GR group (n = 15) exhibited higher postD, ∆%ADC and ∆%D values than the PR group (n = 27) (all P < 0.05). Based on ROC analysis, ∆%D had a higher area under the curve value than ∆%ADC (P = 0.009) in discriminating the pCR from non-pCR groups. In conclusion, IVIM-DWI may be helpful in identifying the pCR to nCRT for LARC and is more accurate than traditional DWI.
Highlights
Neoadjuvant chemoradiotherapy followed by total mesorectal excision (TME) has become a standard treatment in patients with locally advanced rectal cancer (LARC)[1], which could decrease the loco-regional recurrence rate and even increase overall survival
This study focused on the feasibility of IVIM-diffusion-weighted imaging (DWI) in discriminating the pathological response to Neoadjuvant chemoradiotherapy (nCRT) in patients with LARC
Our data found that the pre-nCRT perfusion parametric value and post-nCRT pure diffusion values exhibit significant correlations with the pathological response (TRG score) for LARC
Summary
Neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision (TME) has become a standard treatment in patients with locally advanced rectal cancer (LARC)[1], which could decrease the loco-regional recurrence rate and even increase overall survival. After nCRT, approximately 15%–27% of LARC patients achieved a pathologic complete response (pCR)[2, 3]. These patients have a favourable long-term outcome with excellent local control and disease-free survival. Based on the bi-exponential model[14], intravoxel incoherent motion DWI (IVIM-DWI) can separately quantitate the pure diffusion motion and perfusion- related motion of water molecules without using an exogenous contrast agent. To the best of our knowledge, the feasibility of IVIM-DWI in identifying the tumour pathological response of LARC to nCRT has not been well determined, especially discriminating pCR from non-pCR, a recent study investigated the utility of IVIM-DWI in separating PR from GR.
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