Strategies to evaluate the impact of rectal volume on prostate motion during three-dimensional conformal radiotherapy for prostate cancer.

To evaluate the rectal volume influence on prostate motion during three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer.

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.

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).

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.

Radiologia brasileira. 0000 [Epub]

Ana Paula Diniz Fortuna Poli, Rodrigo Souza Dias, Adelmo José Giordani, Helena Regina Comodo Segreto, Roberto Araujo Segreto

PhD, Physician Assistant, Unit of Radiotherapy, Centro de Atenção Integrada à Saúde da Mulher - Universidade Estadual de Campinas (CAISM-Unicamp), Campinas, SP, Brazil., 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., 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., 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., 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.