AbstractID: 7066 Title: Comparison of 3D Conformal and Intensity-Modulated Radiation Therapy for
Treatment of Prostate Cancer
Three-dimensional conformal radiation therapy and intensity-modulated radiation therapy
(IMRT) are both used to treat early-stage prostate cancer. A planning study was
performed on twenty patients to compare the effectiveness of these treatment techniques.
The clinical target volume consisted of the prostate and inferior half of the seminal
vesicles. The critical organs included rectum, bladder, and femoral heads. Four
conformal plans were developed for each patient - a 10-field plan, two 7-field plans with
different lateral beam weighting, and a 4-field plan. Two IMRT plans were also
developed – one for dynamic multileaf collimator (DMLC) delivery and the other for
NOMOS MIMiC delivery. The prescription was 75.6 Gy in 42 fractions to the PTV for
all plans except the 10-field plan, which delivered 78 Gy in 39 fractions to the isocenter.
Plans were compared based on dose volume histograms, mean tumor doses, and
minimum tumor doses. The volume of rectum irradiated above 70 Gy was 23-50% less
for the IMRT plans compared to the conformal plans. The bladder volume irradiated
above 70 Gy was up to 30% less for the IMRT plans. Mean prostate doses were 82.4-82.9
Gy for the IMRT plans and 78.4-79.5 Gy for the conformal plans. The percentage
volume of the PTV receiving more than 78 Gy was 97% for the IMRT plans, 73% for the
7-field and 4-field plans, and 44% for the 10-field plans. Both IMRT techniques
achieved a higher mean target dose with a lower dose delivered to the critical structures
compared to the conformal techniques.