Motion during radiation therapy can be categorized as inter-fraction (changes in anatomy that occur between treatment days) and intra-fraction (changes that occur during the "beam on" window of treatment delivery). Inter-fraction motion is managed by adaptive radiotherapy (ART), the process of making changes in the treatment plan while the patient remains on the treatment table. This is now a standard-of-care therapy within Washington University's clinic. Intra-fraction motion is managed by gated and non-gated delivery techniques. Varian Medical Systems has integrated the necessary components into a CT-guided radiotherapy device (ETHOS). In the ETHOS, Varian has built a device that integrates on-board cone beam CT imaging capable of delineating target and organ-at-risk positions and a dedicated artificial intelligence-driven treatment planning system for inter-fraction motion management as well as a paired optical surface image guidance system for intra-fraction motion management. Although online ART is a standard-of-care practice in the clinic and has previously been shown to be feasible, use of surface-guidance for intra-fraction gating of abdominal and thoracic SBRT on ETHOS is novel.

Therefore, in this study, the investigators propose to evaluate the feasibility and safety of using a novel surface guidance beam-gating system, incorporated with a CBCT-guided adaptive radiotherapy platform, to manage respiratory motion during delivery of CT-guided stereotactic radiotherapy. To best assess the utility of this technology to manage respiratory motion, the investigators will focus on disease sites that are highly affected by respiratory motion: upper abdominal or lower thoracic malignancies.

Inclusion Criteria:

• Primary or metastatic disease of the abdomen or lower thorax, with biopsy-proven or radiographically diagnosed disease histology of solid tumor categorization, with the exception of small cell cancers.
• Must be medically fit for SBRT as determined by the treating physician, with at least one disease site to be deemed suitable for treatment with CT-guided stereotactic radiation to the abdomen or thorax as per radiation oncologist evaluation.
• At least 18 years of age.
• Karnofsky performance status > 60
• Capable of single deep inspiratory breath-hold or end-exhale breath-hold of at least 17 seconds in duration and of repeated end-exhale or deep inspiratory breath-hold of at least 10 seconds in duration upon verbal instruction.
• Must have completed any systemic therapy at least one week prior to planned start of SBRT (two weeks preferred), and must have no plans to initiate systemic therapy for at least one week following end of SBRT (two weeks preferred).
• Able to understand and willing to sign an IRB approved written informed consent document (or that of legally authorized representative, if applicable).

Exclusion Criteria:

• Past history of radiotherapy within the projected treatment field of any of the disease sites to be treated by CT-guided SBRT.
• Currently receiving any investigational agents.
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Pregnant and/or breastfeeding. Patient must have a negative pregnancy test within 14 days of study entry.

Individual participant data that underlie the results reported in this article, after deidentification (text, tables, figures, and appendices) that will be used for individual participant data meta-analysis.

Beginning 9 months and ending 36 months following article publication.

Investigators whose proposed use of the data has been approved by an independent review committee identified for this purpose. Proposals may be submitted to the primary contact for this study.