title: Dosimetric advantages and superior treatment delivery efficiency of RapidArc over conventional intensity-modulated radiotherapy in high-risk prostate cancer involving seminal vesicles and pelvic nodes.
abstract: OBJECTIVE
  To compare the dosimetry and treatment delivery efficiency of RapidArc with conventional intensity-modulated radiotherapy (IMRT) in the treatment of high-risk prostate cancer.
  
  
  METHODS
  Fifteen patients with high-risk localised prostate cancer were studied. Sequential treatment was used. The initial planning target volume (PTV-L) included the prostate, seminal vesicles and pelvic lymphatics, whereas the prostate boost PTV (PTV-P) included the prostate and seminal vesicles only. The total prescription dose was 76 Gy (44 Gy to PTV-L, 32 Gy to PTV-P; 2 Gy/fraction). Two separate planning techniques were generated for each patient: seven static-field IMRT versus two-arc RapidArc. Dose-volume parameters for the organs at risk, conformity index and homogeneity index for the PTVs, the calculated monitor units and treatment delivery time for both techniques were compared.
  
  
  RESULTS
  RapidArc gave more conformal plans than IMRT for both PTVs. RapidArc gave a higher homogeneity index to the PTV-P and a similar homogeneity index to the PTV-L. The two techniques gave similar dosimetric results for the rectum, bladder and femoral heads. The mean dose (Dmean) and the maximum dose (Dmax) of the bowel space were reduced by 3.06 and 2.83%, respectively, with RapidArc. The V20 Gy, V30 Gy and V40 Gy for healthy tissues were reduced by 7.77, 14.25 and 17.55%, respectively, with RapidArc. The calculated treatment delivery time and monitor units were reduced by 74.09%/60.93% and 68.32%/48.06% for the PTV-L/PTV-P, respectively, with RapidArc.
  
  
  CONCLUSIONS
  RapidArc is better than conventional IMRT in terms of dosimetry and delivery efficiency for high-risk prostate cancer.
authors: Department of Clinical Oncology, State Key Laboratory in Oncology in South China, Sir YK Pao Centre for Cancer, Hong Kong Cancer Institute and Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: mc_poon@clo.cuhk.edu.hk.
authors: D M C
authors: DM
authors: Poon
authors: M
authors: M
authors: Kam
authors: C M
authors: CM
authors: Leung
authors: R
authors: R
authors: Chau
authors: S
authors: S
authors: Wong
authors: W Y
authors: WY
authors: Lee
authors: K C W
authors: KC
authors: Wong
authors: B
authors: B
authors: Yu
authors: A
authors: A
authors: Chan
mesh_terms: D006801:Humans; D008198:Lymph Nodes / Q000473:pathology / Q000528:radiation effects*; D008297:Male; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011835:Radiation Protection / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D012307:Risk Factors; D012669:Seminal Vesicles / Q000473:pathology / Q000528:radiation effects*
keywords: Intensity-modulated radiotherapy; prostate cancer; volumetric radiotherapy