ABSTRACT
Abstract Objective: To evaluate the rectal volume influence on prostate motion during three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer. Materials and 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 cm3 had a significant influence on the prostate motion in the anteroposterior direction ( p = 0.045). Conclusion: 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 cm3. Therefore, the treatment of patients with a rectal volume > 70 cm3 should be re-planned with appropriate rectal preparation.
Resumo Objetivo: Avaliar a influência do volume retal na movimentação da próstata durante a radioterapia tridimensional conformacional (3D-CRT) para câncer de próstata. Materiais e Métodos: Cinquenta e um pacientes com câncer de próstata foram submetidos a três tomografias seriadas, sendo a primeira de planejamento e duas durante a 3D-CRT. Os órgãos de interesse foram delineados. O contorno da próstata foi comparado ao exame inicial em relação aos seus limites anterior, posterior, superior, inferior e laterais. As variações dos limites anterior do reto e de seu volume foram avaliadas e correlacionadas à movimentação da próstata no sentido anteroposterior. Resultados: As maiores variações na próstata foram observadas no sentido superoinferior, seguido pelo anteroposterior. Observou-se correlação significante da movimentação da próstata com a variação do volume do reto ( p = 0,037). O volume retal inicial superior a 70 cm3 influenciou significativamente na maior movimentação da próstata no sentido anteroposterior ( p = 0,045). Conclusão: Este estudo mostrou que a próstata apresenta significativa movimentação interfração durante a 3D-CRT, apresentando maiores variações nos sentidos superoinferior e anteroposterior, e que um volume retal inicial superior a 70 cm3 influencia na movimentação da próstata. Desta forma, os pacientes com volume retal superior a 70 cm3 devem ser replanejados com preparo retal adequado.
ABSTRACT
PURPOSE: To determine whether large rectal volume on planning computed tomography (CT) results in lower tumor regression grade (TRG) after neoadjuvant concurrent chemoradiotherapy (CCRT) in rectal cancer patients. MATERIALS AND METHODS: We reviewed medical records of 113 patients treated with surgery following neoadjuvant CCRT for rectal cancer between January and December 2012. Rectal volume was contoured on axial images in which gross tumor volume was included. Average axial rectal area (ARA) was defined as rectal volume divided by longitudinal tumor length. The impact of rectal volume and ARA on TRG was assessed. RESULTS: Average rectal volume and ARA were 11.3 mL and 2.9 cm². After completion of neoadjuvant CCRT in 113 patients, pathologic results revealed total regression (TRG 4) in 28 patients (25%), good regression (TRG 3) in 25 patients (22%), moderate regression (TRG 2) in 34 patients (30%), minor regression (TRG 1) in 24 patients (21%), and no regression (TRG0) in 2 patients (2%). No difference of rectal volume and ARA was found between each TRG groups. Linear correlation existed between rectal volume and TRG (p = 0.036) but not between ARA and TRG (p = 0.058). CONCLUSION: Rectal volume on planning CT has no significance on TRG in patients receiving neoadjuvant CCRT for rectal cancer. These results indicate that maintaining minimal rectal volume before each treatment may not be necessary.