Quido G de Lussanet MD, Presenter: Nothing to Disclose

Walter H Backes PhD, Abstract Co-Author: Nothing to Disclose

Coen I Baeten MD, Abstract Co-Author: Nothing to Disclose

Geerard L Beets PhD, Abstract Co-Author: Nothing to Disclose

Jos M.A. van Engelshoven PhD, Abstract Co-Author: Nothing to Disclose

Regina G. H. Beets-Tan MD, PhD, Abstract Co-Author: Nothing to Disclose

Dynamic contrast-enhanced T1-weighted magnetic resonance imaging (DCE-MRI) using gadopentetate dimeglumine in mouse colorectal cancer models has demonstrated positive relationships between DCE-MRI derived parameters and histology. The purpose of this study was to evaluate DCE-MRI in monitoring effects of neoadjuvant radiation therapy in rectal cancer patients.

DCE-MRI was performed in 18 patients with curable primary rectal cancer. Seven underwent a long course of preoperative radiation therapy (Long-RT) (25x 1.8 Gy), prior to DCE-MRI. Eleven did not, of whom, 3 underwent a short course of preoperative radiation therapy (Short -RT) (5x5 Gy), after MR imaging. DCE-MRI included pre-contrast T1-weighted measurements and a T1-W dynamic contrast-enhanced series of 250 dynamic volume acquisitions (duration of dynamic series, 10 minutes). A pharmacokinetic two-compartment model was used for calculating the microvessel transfer coefficient (KPS) and reflux (k) for the whole tumor volume. In addition, the extracellular extravascular space (EES) was defined as EES = KPS / k.Two observers independently scored microvessel density (CD31 and CD34 antibody) and tumor cell (Ki67) proliferation during the immunohistochemic analyses after surgery.

Long-RT resulted in significant reductions of 68% (p=.03) in KPS and 75% (p=.001) in k, and a 27% (ns, p=.1) increase in EES. Histology showed reductions of 34% in microvessel density (p=.04) and 55% (p=.002) in Ki67 positive tumor cells. The 3 patients who underwent short-RT after DCE-MRI, showed no differences in KPS, k or EES (p>.3) compared to patients without RT, however, effects of RT were evident in histology: reduction of 53% (p=.02) in Ki76 positive tumor cells, but no reductions in MVD (p>.5).

DCE-MRI combined with pharmacokinetic modeling showed effects of neoadjuvant radiation treatment in patients with curable primary rectal cancer. Reductions in KPS and k after a long course of radiation therapy probably reflect a combination of reduced tumor vascularity and increased EES, including edema and necrosis, secondary to radiation. Greater reductions in k than in KPS might be explained by the (ns) increase in EES.

de Lussanet, Q, Backes, W, Baeten, C, Beets, G, van Engelshoven, J, Beets-Tan, R, Dynamic Contrast-enhanced MRI Combined with Pharmacokinetic Modeling Can Monitor Effects of Neoadjuvant Radiation Therapy in Patients with Curable Primary Rectal Cancer Compared with Histologic CD31/34 and Ki67 Analysis.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4413987.html