A study of image-guided intensity-modulated radiotherapy with fiducials for localized prostate cancer including pelvic lymph nodes.
OBJECTIVE
To study the impact on nodal coverage and dose to fixed organs at risk when using daily fiducial localization of the prostate to deliver intensity-modulated radiotherapy (IMRT).


METHODS
Five patients with prostate cancer in whom prostate and pelvic nodes were irradiated with IMRT were studied. Dose was prescribed such that 95% of the prostate planning target volume (PTV) and 90% of the nodal PTV were covered. Random and systematic prostate displacements in the anterior-posterior, superior-inferior, and left-right directions were simulated to shift the original isocenter of the IMRT plan. The composite dose during the course of treatment was calculated.


RESULTS
Compared with a static setup, simulating random shifts reduced dose by less than 1.5% for nodal hotspot (i.e., dose to 1 cm(3)), by less than 1% for the 90% nodal PTV coverage, and by less than 0.5% for the nodal mean dose. Bowel and femoral head hotspots were reduced by less than 1.5% and 2%, respectively. A 10-mm systematic offset reduced nodal coverage by up to 10%.


CONCLUSIONS
The use of prostate fiducials for daily localization during IMRT treatment results in negligible changes in dose coverage of pelvic nodes or normal tissue sparing in the absence of a significant systematic offset. This offers a simple and practical solution to the problem of image-guided radiotherapy for prostate cancer when including pelvic nodes.
Hsu
Annie
A
Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA 94305-5847, USA.
Pawlicki
Todd
T
Luxton
Gary
G
Hara
Wendy
W
King
Christopher R
CR
D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects; D008207:Lymphatic Metastasis; D008297:Male; D009928:Organ Specificity; D010386:Pelvic Neoplasms / Q000532:radiotherapy*; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*