Apparent diffusion coefficient for lymph node characterization after chemoradiation therapy for locally advanced rectal cancer

Abstract

Background

Because further treatment plans depends on lymph node (LN) status after neoadjuvant chemoradiation therapy (CRT), the accurate characterization of LN is important.

Purpose

To evaluate the diagnostic performance of apparent diffusion coefficient (ADC) for LN characterization after CRT and to compare the performance with that of LN size.

Material and Methods

Fifty-three patients (36 men, 17 women; mean age, 58 years; age range, 34–79 years) who underwent CRT and subsequent surgery were included. All patients underwent 1.5-T magnetic resonance imaging (MRI). Each regional LN on post-CRT MRI was identified in consensus by two radiologists after reviewing the pre-CRT MRI. The ADC value and size in each LN was measured. To compare the mean ADC values and sizes of the metastatic and non-metastatic LNs after CRT, the t-test was used. To calculate the performance, a ROC curve analysis was performed. The histopathological examinations served as the reference standard.

Results

A total of 115 LNs (29 metastatic and 86 non-metastatic) were matched and analyzed. The mean ADC of the metastatic LNs was significantly higher than that of the non-metastatic LNs (1.36 ± 0.27 × 10^–3mm²/s; 1.13 ± 0.23 × 10^–3mm²/s, P < 0.0001). The mean size of the metastatic LNs was also significantly larger than that of the non-metastatic LNs (5.6 ± 3.1; 3.9 ± 1.2, P = 0.0078). There was no significant difference between the areas under the curve of the ADC and size (0.742 [95% CI, 0.652–0.819]; 0.680 [0.586–0.764], respectively, P = 0.4090).

Conclusion

The performance of ADC for LN characterization after CRT was comparable to that of LN size.