Intensity modulated neutron radiotherapy for the treatment of adenocarcinoma of the prostate.
OBJECTIVE
This study investigates the enhanced conformality of neutron dose distributions obtainable through the application of intensity modulated neutron radiotherapy (IMNRT) to the treatment of prostate adenocarcinoma.


METHODS
An in-house algorithm was used to optimize individual segments for IMNRT generated using an organ-at-risk (OAR) avoidance approach. A number of beam orientation schemes were investigated in an attempt to approach an optimum solution. The IMNRT plans were created retrospectively for 5 patients previously treated for prostate adenocarcinoma using fast neutron therapy (FNT), and a comparison of these plans is presented. Dose distributions and dose-volume histograms (DVHs) were analyzed and plans were evaluated based on percentage volumes of rectum and bladder receiving 95%, 80%, and 50% (V(95), V(80), V(50)) of the prescription dose, and on V(60) for both the femoral heads and GM(muscle) group.


RESULTS
Plans were normalized such that the IMNRT DVHs for prostate and seminal vesicles were nearly identical to those for conventional FNT plans. Use of IMNRT provided reductions in rectum V(95) and V(80) of 10% (2-27%) and 13% (5-28%), respectively, and reductions in bladder V(95) and V(80) of 12% (3-26%) and 4% (7-10%), respectively. The average decrease in V(60) for the femoral heads was 4.5% (1-18%), with no significant change in V(60) for the GM(muscle) group.


CONCLUSIONS
This study provides the first analysis of the application of intensity modulation to neutron radiotherapy. The IMNRT technique provides a substantial reduction in normal tissue dose in the treatment of prostate cancer. This reduction should result in a significant clinical advantage for this and other treatment sites.
Department of Radiation Oncology, Washington University, St. Louis, MO 63110-1093, USA. lsantanam@radonc.wustl.edu
Lakshmi
L
Santanam
Tony
T
He
Mark
M
Yudelev
Jeffrey D
JD
Forman
Colin G
CG
Orton
Frank Vanden
FV
Heuvel
Richard L
RL
Maughan
Jay
J
Burmeister
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D000465:Algorithms; D005270:Femur Head / Q000528:radiation effects; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000528:radiation effects; D009502:Neutrons / Q000627:therapeutic use*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards; D012007:Rectum / Q000528:radiation effects; D012669:Seminal Vesicles / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects