Treatment planning guidelines regarding the use of CT/PET-guided IMRT for cervical carcinoma with positive paraaortic lymph nodes.
OBJECTIVE
Computed tomography (CT)/positron emission tomography (PET)-guided intensity-modulated radiotherapy of the paraaortic lymph nodes (PALNs) has been proposed for patients with cervical carcinoma and paraaortic metastasis. This investigation attempted to determine the guidelines regarding the selection of appropriate treatment parameters (e.g., number of beams, beam geometry) and organ-specific parameters (e.g., importance weighting and tolerance dose) for intensity-modulated radiotherapy planning for the PALNs.


METHODS
Patients underwent imaging using CT and PET. The images were registered, and the structures were contoured. A goal dose of 50.4 Gy and 59.4 Gy was assigned to the clinical target volume (lymph node bed) and gross tumor volume (PET-delineated PALNs), respectively. For each patient, multiple treatment plans using various beam geometries and planning parameters were executed and evaluated in terms of the dose-volume histograms of the target and critical structures.


RESULTS
Acceptable sparing of the stomach, liver, and colon was achieved, regardless of the number of beams used. Sparing of the spinal cord was strongly dependent on the number and arrangement of the beams. Varying the number and arrangement of the beams affected small intestine sparing, but the amount of sparing was limited because the small intestine overlapped the target volumes, and, therefore, received the prescription dose. Adjusting the number of beams, beam angles, and prescription parameters provided minimal improvement in kidney sparing.


CONCLUSIONS
We successfully developed treatment plans that deliver 59.4 Gy to the positive PALNs and 50.4 Gy to the paraaortic region using CT/PET-guided intensity-modulated radiotherapy.
Esthappan
Jacqueline
J
Department of Radiation Oncology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA. esthappan@wustl.edu
Mutic
Sasa
S
Malyapa
Robert S
RS
Grigsby
Perry W
PW
Zoberi
Imran
I
Dehdashti
Farrokh
F
Miller
Tom R
TR
Bosch
Walter R
WR
Low
Daniel A
DA
D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007421:Intestine, Small / Q000000981:diagnostic imaging; D007668:Kidney / Q000000981:diagnostic imaging; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods* / Q000592:standards; D014055:Tomography, Emission-Computed; D014057:Tomography, X-Ray Computed; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18