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NCT Number: NCT07221058

Adaptive Radiation Boost for Rectal Cancer

The goal of this clinical trial is to find out if giving extra adaptive radiation therapy after standard chemoradiation treatment is safe and helpful for people with rectal cancer.

The main questions the study aims to answer are:

* Can this approach help target the most aggressive cancer cells more accurately, while protecting nearby healthy tissue? * Can it reduce the side effects that people may experience during treatment?

Participants will:

* First receive standard treatment: radiation (45 Gy in 25 sessions) along with a chemotherapy pill called capecitabine. * Then get extra radiation using MRI scans every two weeks to adjust the treatment based on how the tumor responds. * Use a small balloon during treatment to help aim the radiation and protect healthy areas. * Finally, receive additional chemotherapy (such as FOLFOX) for four months.

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Key information

Conditions

Rectum Cancer, Adenocarcinoma Adenocarcinoma Carcinoma Colorectal Neoplasms Digestive System Diseases Digestive System Neoplasms Gastrointestinal Diseases Gastrointestinal Neoplasms Intestinal Diseases Intestinal Neoplasms Neoplasms Neoplasms by Histologic Type Neoplasms by Site Neoplasms, Glandular and Epithelial Rectal Diseases Rectal Neoplasms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1

Primary location

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Subjects must have histologically or cytologically confirmed rectal adenocarcinoma.
  • Subjects must have T2-3, N0-1, M0 rectal cancer. Staging will be done by MRI pelvis and CT chest and abdomen with contrast. PET-CT will be an acceptable alternative for the CT chest and abdomen.
  • Subjects must be willing to undergo MRI scans.
  • Age ≥18 years.
  • ECOG performance status 0 or 1.
  • Estimated survival of ≥ 12 months.
  • Subjects must have normal organ and marrow function as defined below
  • Absolute neutrophil count > =1,000/mcL
  • Platelets >= 75,000/mcL
  • Total bilirubin < 3 mg/dL
  • Subjects must be able to tolerate the chemotherapy regimens outlined in the treatment plan (Section 5.0), both before and after ART.
  • Before ART: Capecitabine at a dose of 825 mg/m²
  • After ART: FOLFOX combination chemotherapy, or 5-FU, or capecitabine
  • Subjects must possess the ability to understand and willingness to sign a written informed consent and HIPAA consent document. Translation services including translation of informed consent documents will be provided, as feasible, to encourage diversity of inclusion of eligible patients.

Exclusion criteria

  • Subjects who have been previously treated for rectal cancer are excluded.
  • Subjects with rectal cancer involving the anal canal are excluded. (Rectal cancer abutting the anal canal will be allowed.)
  • Subjects must not be receiving any other investigational agents.
  • Subjects may not have had prior pelvic radiation.
  • Subjects should not have had a cancer actively treated within the last 3 years, excluding non-melanoma skin cancer.
  • Subjects must not have 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.
  • Any condition or significant co-morbidity that prevents safe delivery of ART per the discretion of the treating physician(s).
  • Subjects must not be pregnant or breast-feeding.

Treatment and study plan

Adaptive Radiotherapy Boost

Radiation

Patients will receive one boost fraction every two weeks, targeting the primary tumor within the rectum plus a 2 mm Planning Target Volume (PTV) margin. Any regional lymph nodes that measure at least 5 mm in short axis on the day of treatment will receive treatment with the ART dose being given to the primary rectal tumor.

Primary outcomes

  1. MTD will be evaluated by monitoring the rate of dose limiting toxicities (DLTs) defined as acute Grade 2+ gastrointestinal toxicity probably or definitely related to radiation.

    Time frame: From the initiation of rectal adaptive radiotherapy boost to 90 days after the last dose of boost, for a total of ~ 120 days.

  2. Feasibility of a rectal boost that targets at least 90% of the rectal planning tumor volume with the 80% prescribed dose while limiting the outer 3 mm of the rectal wall to no more than 50% of the prescription dose delivered to 0.1cc.

    Time frame: From the ART boost initiation to the end of the ART boost, for a period of ~ 5 weeks

    Feasibility will be determined based on successful implementation and completion of standard chemoradiotherapy followed by experimental rectal adaptive radiotherapy boost utilizing CT-MR fusion that targets at least 90% of the rectal PTV_Eval with the 80% prescribed dose while limiting the outer 3 mm of the rectal wall to no more than 50% of the prescription dose delivered to 0.1cc in ≥ 70% of ART fractions for the patient population enrolled in the study. This will be assessed at the MTD.

Secondary outcomes

  1. Estimate the efficacy of bi-weekly adaptive radiotherapy boost fractions by complete response rate, near complete response rate, and incomplete response rate as per Memorial Sloan Kettering Cancer Center (MSKCC) criteria.

    Time frame: From the end of rectal adaptive radiotherapy boost to the end of study, for a total of ~ 5 years.

  2. Estimate total mesorectal excision (TME) free survival following treatment with the study regimen.

    Time frame: From the end of treatment to the end of the study, for a total of up to 5 years.

  3. Estimate overall survival (OS) following treatment with the study regimen.

    Time frame: From the end of treatment to the end of study, for a total of up to 5 years.

  4. Estimate early and late toxicity following treatment with the study regimen.

    Time frame: From the initiation of rectal radiation boost treatment to the end of the study, for a total of ~ 5 years.

Study contacts

Contact information is provided by the study sponsor or research team.

Jianli Hu, MD, PhD

CONTACT

[email protected]

267-449-1431

Joshua Meyer, MD

CONTACT

[email protected]

215-728-2667

Sponsors and collaborators

Lead sponsor

Fox Chase Cancer Center

Other

Collaborators

  • Varian Medical Systems

Registry information

Official study title

Adaptive Radiation BOost for Rectal Cancer: a Phase I Dose Escalation Study (ARBOR)

Acronym: ARBOR

Important dates

Study start
2025
Primary completion
2028
Study completion
2029
First posted
Oct 27, 2025
Registry last updated
Dec 9, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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