title: Strategies to evaluate the impact of rectal volume on prostate motion during three-dimensional conformal radiotherapy for prostate cancer.
abstract: OBJECTIVE
  To evaluate the rectal volume influence on prostate motion during three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer.
  
  
  METHODS
  Fifty-one patients with prostate cancer underwent a series of three computed tomography scans including an initial planning scan and two subsequent scans during 3D-CRT. The organs of interest were outlined. The prostate contour was compared with the initial CT images considering the anterior, posterior, superior, inferior and lateral edges of the organ. Variations in the anterior limits and volume of the rectum were assessed and correlated with prostate motion in the anteroposterior direction.
  
  
  RESULTS
  The maximum range of prostate motion was observed in the superoinferior direction, followed by the anteroposterior direction. A significant correlation was observed between prostate motion and rectal volume variation (p = 0.037). A baseline rectal volume superior to 70 cm(3) had a significant influence on the prostate motion in the anteroposterior direction (p = 0.045).
  
  
  CONCLUSIONS
  The present study showed a significant interfraction motion of the prostate during 3D-CRT with greatest variations in the superoinferior and anteroposterior directions, and that a large rectal volume influences the prostate motion with a cutoff value of 70 cm(3). Therefore, the treatment of patients with a rectal volume > 70 cm(3) should be re-planned with appropriate rectal preparation.
authors.affiliation: PhD, Physician Assistant, Unit of Radiotherapy, Centro de Atenção Integrada à Saúde da Mulher - Universidade Estadual de Campinas (CAISM-Unicamp), Campinas, SP, Brazil.
authors.forename: Ana Paula Diniz Fortuna
authors.initials: AP
authors.lastname: Poli
authors.affiliation: PhD, Physician responsible, Unit of Radiotherapy, Department of Clinical and Experimental Oncology, Escola Paulista de Medicina da Universidade Federal de São Paulo (EPM-Unifesp), São Paulo, SP, Brazil.
authors.forename: Rodrigo Souza
authors.initials: RS
authors.lastname: Dias
authors.affiliation: PhD, Physicist responsible, Unit of Radiotherapy, Department of Clinical and Experimental Oncology, Escola Paulista de Medicina da Universidade Federal de São Paulo (EPM-Unifesp), São Paulo, SP, Brazil.
authors.forename: Adelmo José
authors.initials: AJ
authors.lastname: Giordani
authors.affiliation: Post-doc Fellow, Associate Professor, Unit of Radiotherapy, Department of Clinical and Experimental Oncology, Escola Paulista de Medicina da Universidade Federal de São Paulo (EPM-Unifesp), São Paulo, SP, Brazil.
authors.forename: Helena Regina Comodo
authors.initials: HR
authors.lastname: Segreto
authors.affiliation: Private Docent, Associate Professor, Unit of Radiotherapy, Department of Clinical and Experimental Oncology, Escola Paulista de Medicina da Universidade Federal de São Paulo (EPM-Unifesp), São Paulo, SP, Brazil.
authors.forename: Roberto Araujo
authors.initials: RA
authors.lastname: Segreto
keywords: Prostate cancer; Rectal volume; Three-dimensional conformal radiotherapy