.1 Three-dimensional Conformal Radiotherapy Of Prostate Cancer Uncertainties Analysis Of The Prognostic Significance Of Maxillary Sinus Squamous Cell Carcinoma Of Pathological Response Of Preoperative Radiotherapy

PurposeTo investigate the spatial distribution of set-up errors for patients treated with three-dimensional (3D) conformal radiation therapy for pelvic carcinoma and to provide referential safe margins out of CTV during treatment plan design. Materials and MethodsFive patients with rectal or prostate cancers entered the study. All were treated with three-dimensional conformal radiotherapy in a prone position. Belly board was used. Thermoplastic cast was used for immobilization. Measurements were made on a daily basis setup under five consecutive treatments. During patients positioning, gold particles were placed on the skin markers, one in the lateral, and the other in the back. Portal films from two projections (one anterior-posterior and one opposite lateral) were taken after the reticule localizer was inserted to the head of accelerator. Fifty portal films from 25 setups were analyzed. The spatial distribution of set-up errors from left-right, superior-inferior and anterior-posterior directions were evaluated comparing to the first set-up films (representing the standard treatment position).ResultsThe magnitude of set-up errors from 25 positionings in 5 patients differed from patient to patient and day to day. Maximal set-up errors were inspected in the anterior-posterior direction, with a mean of 0.98±0.68 cm (X±SD), 9 of 20 measurements (45%) were > or =1 cm, and two in the 9 measurements were > or =2 cm; The set-up errors for superior-inferior were 0.5-0.7±0.45 cm (X±SD), and the average magnitude from anterior-posterior films was smaller than that from opposite lateral films, 0.51±0.46 cm and 0.70±0.45 cm, respectively. There were 4 and 7 times of > or =1 cm superior-inferior displacements measured from anterior-posterior films and lateral films respectively; the...