Dose distribution in 3-dimensional conformal radiotherapy for prostate cancer: comparison of two treatment techniques (six coplanar fields and two dynamic arcs).
OBJECTIVE
To compare dose distribution for two techniques of 3-dimensional conformal radiotherapy (RT): 6-field technique (6F) and 2-dynamic arc therapy (2DA).


METHODS
Thirty nonmetastatic prostate cancer patients were included. In each patient, two treatment plans were prepared: with six coplanar fields (45 degrees , 90 degrees , 135 degrees , 225 degrees , 270 degrees , 315 degrees ) and with two dynamic lateral 100 degrees -wide arcs (40-140 degrees , 220-320 degrees ). Dose-volume histograms (DVHs) were computed and mean area under curve (AUC) values were calculated for the DVHs of Planning Target Volume (PTV), rectum, urinary bladder and femoral heads. Doses given to 30% of rectum (DR(30)), to 60% of rectum (DR(60)), to 50% of bladder (DB(50)), to 50% of femoral head (DF(50)) and to 95% of PTV (DPTV(95)) were reported as a percentage of the total dose.


RESULTS
Mean DR(30) and DR(60) for 6F and 2DA were 75.8%, 51.5% and 72.2%, 37.2%, respectively. Mean DB(50) for 6F and 2DA were 68% and 64.2%, respectively. Mean right DF(50) for 6F and 2DA were 35.4% and 45.5%, respectively. Mean DPTV(95) for 6F and 2DA were 99% and 99.2%, respectively. Mean AUCs of DVHs of rectum and urinary bladder were significantly higher for 6F (this was more evident for small PTV and in the intermediate dose range). Mean AUC of DVHs of PTV and femoral heads were significantly higher for 2DA.


CONCLUSIONS
Both 6F and 2DA offer good dose distribution for PTV. 2DA allows for significantly better sparing of rectum and urinary bladder with slightly worse femoral head dose distribution. Further study is warranted in order to establish the clinical relevance of these differences.
Jereczek-Fossa
Barbara Alicja
BA
Department of Radiation Oncology; University of Milan, Milan, Italy. barbara.fossa@ieo.it
Cattani
Federica
F
D'Onofrio
Alberto
A
Cambria
Raffaella
R
Kowalczyk
Anna
A
Corallo
Anna
A
Vavassori
Andrea
A
Zerini
Dario
D
Ivaldi
Giovanni Battista
GB
DeCobelli
Ottavio
O
Orecchia
Roberto
R
D000368:Aged; D000369:Aged, 80 and over; D005270:Femur Head / Q000528:radiation effects; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011835:Radiation Protection; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal; D012007:Rectum / Q000528:radiation effects; D012669:Seminal Vesicles / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects