Reduction of rectal dose by integration of the boost in the large-field treatment plan for prostate irradiation.
OBJECTIVE
To reduce the dose in the rectal wall from prostate irradiation at high dose levels.


METHODS
Treatment plans in which the boost fields were integrated into the large fields (simultaneous integrated boost [SIB]) were compared with plans in which the large fields and boost fields were planned individually and applied in a sequential manner (sequential boost). Two target volumes were delineated: PTV1, the target volume of the large fields that is irradiated to 68 Gy, and PTV2, the target volume of the boost fields that is irradiated to 10 Gy. The sequential boost and the SIB were normalized to the mean dose in PTV2, being 78 Gy. We used a five-field intensity-modulated radiotherapy (IMRT) technique, applied in a step and shoot mode, and included beam weight optimization. A set of 5 patients with varying degree of overlap between PTV1 and the rectal wall was used for analysis.


RESULTS
The SIB resulted in a reduction of the dose in the rectal wall. Rectal normal tissue complication probability (NTCP) decreased for the SIB, on average, by a factor of almost 2, compared with the sequential boost.


CONCLUSIONS
The SIB reduced the dose in the rectal wall, compared with the sequential boost technique.
Bos
Luc J
LJ
Radiotherapy Division, The Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands.
Damen
Eugène M F
EM
de Boer
Roel W
RW
Mijnheer
Ben J
BJ
McShan
Daniel L
DL
Fraass
Benedick A
BA
Kessler
Marc L
ML
Lebesque
Joos V
JV
D000230:Adenocarcinoma / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D009426:Netherlands; D055585:Physical Phenomena; D010825:Physics; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000517:prevention & control*; D011835:Radiation Protection; D012007:Rectum