Postoperative irradiation of gynecologic malignancies: improving treatment delivery using aperture-based intensity-modulated radiotherapy.
OBJECTIVE
To evaluate dosimetric and treatment delivery advantages of aperture-based intensity-modulated radiotherapy (AB-IMRT) for the treatment of patients receiving whole pelvic radiotherapy for gynecologic malignancies.


METHODS
Nineteen patients undergoing pelvic radiotherapy after resection of endometrial cancers were selected. A 45-Gy dose was prescribed to the target volume delineated on a planning CT scan. An in-house inverse planning system, Ballista, was used to develop a treatment plan using aperture-based multileaf collimator segments. This approach was compared with conventional four-field, enlarged four-field, and static beamlet-based IMRT (BB-IMRT) techniques in terms of target coverage, dose-volume histogram statistics for surrounding normal tissues, and numbers of segments and monitor units (MU).


RESULTS
Three quarters (76.4%) of the planning target volume received the prescription dose with conventional four-field plans. With adequate target coverage, the Ballista plans significantly reduced the volume of bowel and bladder irradiated at the prescribed dose (p < 0.001), whereas the two approaches provided equivalent results for the rectum (p = 0.5). On the other hand, AB-IMRT and BB-IMRT plans showed only small differences in dose-volume histogram statistics of unknown clinical impact, whereas Ballista plan delivery required on average 73% and 59% fewer segments and MU, respectively.


CONCLUSIONS
With respect to conventional techniques, AB-IMRT for the treatment of gynecologic malignancies provides dosimetric advantages similar to those with BB-IMRT but with clear treatment delivery improvements.
Nadeau
Sylvain
S
Département de physique, de génie physique et d'optique, Université Laval, Québec, QC, Canada. sylvainn@rrsb.nb.ca
Bouchard
Myriam
M
Germain
Isabelle
I
Raymond
Paul-Emile
PE
Beaulieu
Frédéric
F
Beaulieu
Luc
L
Roy
René
R
Gingras
Luc
L
D016889:Endometrial Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D005833:Genital Neoplasms, Female / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D006801:Humans; D007422:Intestines / Q000000981:diagnostic imaging; D011184:Postoperative Period; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D001743:Urinary Bladder / Q000000981:diagnostic imaging