Dong Ik Cha MD, Presenter: Nothing to Disclose

Seong Hyun Kim MD, Abstract Co-Author: Nothing to Disclose

Kyung Mi Jang MD, Abstract Co-Author: Nothing to Disclose

Mi Hee Lee MD, Abstract Co-Author: Nothing to Disclose

To assess causative factors of diffusion restriction on diffusion-weighted imaging (DWI) in patients with pathologic complete response (pCR) after neoadjuvant chemoradiation therapy (CRT) for locally advanced rectal cancer in correlation with pathology.

Forty-three patients with locally advanced rectal cancer (≥T3 or lymph node positive) who underwent neoadjuvant CRT, subsequent surgery, and were diagnosed as pCR were enrolled in this study. All patients underwent pre- and post-CRT 3.0-T rectal MR imaging with DWI. Two radiologists who were blinded to pathologic staging retrospectively reviewed pre- and post-CRT 3.0-T rectal MR imaging for the presence of diffusion restriction in the corresponding tumor on post-CRT DWI by consensus, and which correlated with pathologic findings such as the presence of intramural mucin, and degrees of proctitis and mural fibrosis on surgical specimen. In addition, the pre-CRT tumor volume was measured to define the effect on the degree of radiation proctitis and fibrosis, and intramural mucin.

There were 18 cases (41.9%) of diffusion restriction group and 25 cases (58.1%) of no diffusion restriction group. Diffusion restriction group tended to have more severe proctitis and mural fibrosis in comparison with no diffusion restriction group (p<0.001). There was a tendency that intramural mucin was more common in diffusion restriction group (p= 0.052). The higher pre-CRT tumor volume was significantly correlated with higher degree of proctitis (p=0.0247) and fibrosis (p=0.0445), but not with the presence of intramural mucin (p=0.0944). Severity of proctitis and mural fibrosis were identified as independent determining pathologic factors for diffusion restriction group on multivariate analysis (p= 0.0073 and 0.0011, each).

Both radiation induced proctitis and fibrosis were significant and independent predictors of diffusion restriction in patients with pCR after neoadjuvant CRT for locally advanced rectal cancer, and the pre-CRT tumor volume had significant effect on them.

Diffuse restriction on post-CRT DWI in patients with pCR after neoadjuvant CRT for locally advanced rectal cancer was not rare, and which might be determined by radiation proctitis and mural fibrois.

Cha, D, Kim, S, Jang, K, Lee, M, Pathologic Complete Response with Diffusion Restriction on Diffusion-weighted Imaging after Neoadjuvant Chemoradiation Therapy for Locally Advanced Rectal Cancer: Correlation with Pathologic Findings.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11004724.html