Presenter: Y. Cao Presenter's Affiliation: University of Michigan, Ann Arbor, MI Type of Session: Plenary
High-dose conformal radiation therapy with chemotherapy can prolong the survival of patients with unresectable liver tumors.
Radiation-induced liver disease (RILD) limits the ability to safely deliver high doses.
?Classic? RILD is characterized by anicteric ascites, hepatomegaly, elevation in transaminases (dominated by alkaline phosphatase over other tranaminases), and venous occlusion.
This study sought to characterize liver venous perfusion as a possible predictor of RILD, before, during, and after radiation of liver tumors.
Materials and Methods
Diffusion contrast-enhanced CT scanning was used to determine venous perfusion of liver tissue on a voxel by voxel basis: 8 slices in 2-cm slabs were collected using a breathing control device with coached breathing.
Hepatic arterial and portal venous perfusion components could be resolved.
Serial studies were performed both prior to and after radiotherapy, as follows: after 15 fractions, after 30 fractions, and 1 month after the end of treatment.
Median dose was 67.5 Gy.
Dose-dependent effects were modeled by drawing volumes of interest (VOI) based on isodose curve to establish dose gradients.
Over the course of time, liver venous perfusion decreased in irradiated regions. The magnitude of this effect varied among individuals.
After 15 fractions, there was no significant correlation between dose and perfusion.
After 30 fractions, there was a significant correlation between dose and perfusion (1.6 mL/100 g/min/Gy).
One month after the end of treatment, the significant correlation between dose and perfusion increase with a steepening of the effect (2.5 mL/100 g/min/Gy).
There was a 1.1% reduction in the venous perfusion of the liver 1 month after RT.
The venous perfusion changes after 30 fractions showed individual patient sensitivity to the radiation and a time-delay effect.
This study showed that there was a time- and dose-dependent decrease in liver venous perfusion in the irradiated liver as shown by dynamic contrast-enhanced CT.
This effect did vary among the patients, but it only showed up after 30 fractions, making it difficult to change radiation treatment plans in enough time to avoid toxicity.
However, it is unknown whether these well-quantified differences in liver perfusion will translate into clinically-apparent RILD.
Oct 4, 2011 - Treatment of localized prostate cancer using intensity modulated radiation therapy is associated with a considerable reduction in late bowel and rectal side effects and significantly decreased rectal and bladder toxicity compared to three-dimensional conformal radiation therapy, according to a study presented the annual meeting of the American Society for Radiation Oncology, held from Oct. 2 to 6 in Miami Beach.