Adaptive management of liver cancer radiotherapy

Abstract

Adaptive radiation therapy for liver cancer has the potential to reduce normal tissue complications and enable dose escalation, allowing the potential for tumor control in this challenging site. Using adaptive techniques to tailor treatment margins to reflect patient-specific breathing motions and image-guidance techniques can reduce the high dose delivered to surrounding normal tissues while ensuring that the prescription dose is delivered to the tumor. Several treatment planning and delivery techniques have been developed for use in the liver, including a margin to encompass the full breathing motion, mean position techniques, which evaluate the probability of tumor location during breathing, breath hold, gating, and tracking. Patient selection, clinical workflow, and quality assurance must be considered and developed before integrating these techniques into clinical practice.

Figure 1

Improvements in image guidance with surrogates closer to the tumor: initial alignment, based on lasers (top), based on bony alignment (center), and based on the liver (bottom). Lipidiol in the tumor, visible on CT and CBCT, enables evaluation of the tumor registration.

Figure 2

Axial (left), coronal (center), and sagittal (right) view of the GTV (red), CTV (green), and PTV (blue) shown on the exhale breath hold, contrast enhanced image, with an asymmetric margin based on the individual breathing motion

Figure 3

Methods of measuring breathing motion: cine MR frames (top), 4D CT (upper-middle), online fluoroscopy (lower-middle, right) compared to DRR (left), and 4D CBCT (lower)

Figure 4

Digitally reconstructed radiographs (DRRs) generated from treatment planning images with the fiducials highlighted (left), kV images generated during deliver (center), and the fusion of both images (right). Figure courtesy of Paul J. Keall, Stanford University