Participants who are experiencing abdominal pain due to having cancer in their pancreas may be eligible for this research study. For this type of pain, doctors often recommend radiation therapy to help with the pain. This radiation therapy is called stereotactic body radiotherapy (SBRT). Preparing for SBRT typically takes a week or longer. In this research study, doctors want to test a new workflow in order to shorten the time it takes for participants to receive SBRT to help with their pain.

Doctors typically determine how to administer the SBRT by doing a simulation, which requires a CT (Computerized Tomography) scan. The CT scan is used to create a treatment plan. It can take time to schedule this CT scan and then it takes 5-10 days to create a treatment plan. A way to reduce the planning time for SBRT is to use the CT scan that participants had when their cancer was diagnosed to plan the SBRT. This new workflow can cut down the time it takes to schedule another CT scan and plan for and deliver SBRT. The workflow where doctors use a pre-existing CT scan is called CTsim-free treatment planning. CTsim-free treatment planning is what is being tested in this research study.

Celiac plexus nerve pain, a type of abdominal pain, is common in people with pancreatic cancer. In fact, 70-80% of these people say they have very bad, or debilitating, pain in the lower part of their abdomen and/or the area behind their abdomen where they were diagnosed with pancreatic cancer (1). Recently, a type of treatment called celiac plexus radioablation, which is done using a type of radiation called stereotactic body radiotherapy (SBRT), has been recognized as a new standard-of-care therapy option for these people (2-4).

However, celiac plexus radioablation takes a long time to plan and deliver when compared to traditional treatment approaches, which don't require so much time and so many visits (5). A better workflow is needed to make treatment planning and delivery happen faster. This better workflow should make things easier on people who are experiencing this severe pain and help them start treatment faster to feel better sooner.

One way to create this better workflow for celiac plexus radioablation is to use single-fraction SBRT and to use simulation-free radiation treatment planning. For this type of workflow, pre-existing diagnostic images are used to make the treatment plan, rather than making people get new images before they can start getting treated for their pain (6). This workflow uses an online tool called online adaptive radiotherapy (ART) to help create and adjust the treatment plan based on what can be seen inside the body on the pre-existing diagnostic images so that it targets the right spot.

The research study team has developed an institutional celiac plexus auto-planning template using a commercial CT-guided ART platform. The team has looked back at past cases and confirmed that this workflow can safely create treatment plans in a short amount of time. The adaptive radiotherapy that is used in this simulation-free workflow is a a standard-of-care practice for other disease sites. There have been previous research studies that show that it works to lessen the time to treatment when treating other areas of the body (7-9).

The novel approach in this study is the workflow, and as such, the purpose of this study is to demonstrate the feasibility and safety of a simulation-free workflow for celiac plexus SBRT using online adaptive radiotherapy.

Inclusion Criteria:

• Participants must have histologically or cytologically confirmed cancer that is metastatic or unresectable, and considered appropriate per the treating physician to receive celiac plexus SBRT.

• Age >18 years. Because no data are currently available on the use of celiac axis SBRT in participants ≤18 years of age, children are excluded from this study.

• Performance status: ECOG Performance status ≤ 3

• Severe retroperitoneal pain syndrome (radiates from the lower back to the upper abdomen, belt- like distribution), intensity of at least 5 on 11-point Brief Pain Inventory (BPI, average pain) scale despite analgesic use. Note: previous use of celiac plexus block/neurolysis for pain control is allowed and will be recorded

• Participants must have anatomical involvement of the celiac plexus on the diagnostic CT, PET/CT, or MRI. This includes:

  • Any pancreatic cancer
  • Any other cancer that on imaging demonstrates either gross involvement of the celiac blood vessels or celiac plexus on imaging OR haziness around the celiac blood vessels that typically implies tumor engulfment.

• Prior chemotherapy or biological treatment is allowed, but any active oncological treatment must be stopped at least 1 week prior to radiation therapy and renewed at least 1 week following radiation therapy.

• Participants must have the ability to understand and the willingness to sign a written informed consent document.

• Participants must have a diagnostic CT, PET/CT, or MRI of the abdomen and pelvis, with or without contrast, acquired < 28 days prior to the study consent. This diagnostic scan, to be used for pre-plan formation, must fully visualize the celiac plexus target intended for simulation-free treatment, with full axial field-of-view at the axial levels for treatment. The scan must be of sufficient clinical quality for the treating physician to delineate the target for treatment.

Exclusion Criteria:

• Prior radiotherapy to the upper abdomen.
• Previous radiotherapy to the upper abdomen overlapping with the projected site of treatment.
• Pregnant or breastfeeding women are excluded from this study.
• Participants with conditions associated with increased risk of side effects from radiation such as inflammatory bowel disease and scleroderma.
• Women of childbearing potential must have a negative pregnancy test within 14 days of study entry. If pregnancy test is not clinically indicated as determined by treating physician or protocol principal investigator, documentation of this exception is sufficient in lieu of a pregnancy test.