Objective:

To analyze the correlation between pre-treatment apparent diffusion coefficient (ADC) and histological and immunohistochemical properties of rectal cancer.

Methods:

Forty-nine rectal cancer patients who received surgical resection without neoadjuvant therapy were selected. They underwent primary MRI and diffusion-weighted imaging (DWI). Tumor ADC values were determined and compared with the histological and immunohistochemical results

Results:

Inter-observer a

greement with confidence levels from two separate observers was suitable for ADC measurement (

k

=0.775). The pre-treatment ADC values of T1-2 stage tumors were significantly higher than T3-4 stage ones (

P

=0.001) and the ADC values of N0 stage tumors were significantly higher than to N+ ones (

P

=0.017). The overall trend was that higher T and N stages were correlated with lower ADC values. There was a negative correlation between Ki-67 labelling index (LI) and ADC values (

r

=-0.318

P

=0.026).

Conclusion:

There are significant correlations between pre-treatment ADC values and T stage

N stage and Ki-67 LI. Lower ADC values are associated with more aggressive tumor behaviors. Therefore

ADC value may represent a useful biomarker for assessing the biological features of identified rectal cancer.