Prostate treatment with helical TomoTherapy in patients with bilateral hip prostheses--two case studies

Prostate cancer patients with bilateral hip prostheses require additional planning and treatment considerations. Visualization of the organs at risk (OAR) and the planning target volume (PTV) is hindered by the large amount of artifact streaking between the metallic implants. The density of this area must be accounted for when using heterogeneity correction. Fusion of a megavolt computed tomography (MVCT) to the planning CT aids in viewing the prostate, bladder, and rectum, and implantation of 6 fiducial markers along the posterior border of the prostate helps with the delineation between it and the rectum. When planning, the amount of beam entry angles is limited because of the position of the prostheses and prevents the use of any lateral beams. Therefore, TomoTherapy presents an effective option for these patients because of the ability to use a directional block, which prevents any primary beams from entering through the bilateral hip prostheses (but the beams may exit through the structures), use of MVCT for daily localization, and delivery of radiation with intensity modulation allows for effective sparing of the OAR.