TC36-The Fruit of our Labor: Improvement in Clinical Outcome -

The Example of IMRT and Prostate Cancer

Deborah Kuban, M.D.

M.D. Anderson Cencer Center

Department of Radiation Oncology

Houston, TX 77007

     Over the last several years, with advances in computer planning and treatment technology, new techniques for prostate cancer radiation have rapidly evolved.  Emphasis has been placed on increasing dose while keeping complication rates as low as possible.  To do this, new planning strategies such as Intensity Modulated Radiation Therapy (IMRT) and evaluation methods such as Dose-Volume Histograms (DVH’s) have become necessary.  New treatment technology such as Dynamic Multileaf Collimators (DMLC’s) for conformal beam shaping and methods for organ localization were developed simultaneously.

     Several studies, both randomized and retrospective, show improvement in PSA disease-free survival with higher doses.  Through the use of newer treatment and planning techniques, complication rates have been reduced to acceptably low levels: 5% moderate and 1% severe GI toxicity and 15% moderate and 1% severe GU toxicity.  A study completed at M.D. Anderson Cancer Center showed that the volume of rectum irradiated could be decreased by 25-50% and the amount of bladder by 30% by using IMRT.

     These very conformal techniques with small margins have necessitated better target localization using B-Mode Acquisition and Targeting (BAT), fiducial marker systems, or CT-linac applications.   In addition to organ motion, however, with the prostate, organ deformation is also a significant factor and methods to compensate for this such as image-guided IMRT with daily treatment modification is being explored.