Apparent diffusion coefficient modifications in assessing gastro-oesophageal cancer response to neoadjuvant treatment: comparison with tumour regression grade at histology

To assess changes in apparent diffusion coefficient (Delta ADC) and volume (Delta V) after neoadjuvant treatment (NT), and tumour regression grade (TRG) in gastro-oesophageal cancers (GEC), and to discriminate responders from non-responders. Thirty-two patients with biopsy-proven locally-advanced GEC underwent diffusion weighted magnetic resonance imaging (DWI) pre- and post-NT. Lesion ADC, volume, Delta ADC and Delta V were calculated. TRG 1-2-3 patients were classified as R; TRG 4-5 as non-responders. Delta ADC-TRG and Delta V-TRG correlations, pre-NT and post-NT ADC, Delta ADC and Delta V cut-off values for responders and non-responders were calculated. Two readers measured mean tumour ADCs and interobserver variability was calculated. (Spearman's and intraclass correlation coefficient [ICC]). The interobserver reproducibility was very good both for pre-NT (Spearman's rho = 0.8160; ICC = 0.8993) and post-NT (Spearman's rho = 0.8357; ICC = 0.8663). Responders showed lower pre-NT ADC (1.32 versus 1.63 x 10(-3) mm(2)/s; P = 0.002) and higher post-NT ADC (2.22 versus 1.51 x 10(-3) mm(2)/s; P = 0.001) than non-responders and ADC increased in responders (Delta ADC, 85.45 versus -8.21 %; P = 0.00005). Delta ADC inversely correlated with TRG (r = -0.71, P = 0.000004); no difference in Delta V between responders and non-responders (-50.92 % versus -14.12 %; P = 0.068) and no correlation Delta V-TRG (r = 0.02 P = 0.883) were observed. The ADC can be used to assess gastro-oesophageal tumour response to neoadjuvant treatment as a reliable expression of tumour regression.