Phase 2 Single-Arm Rectal Cancer Brachytherapy for Patients With Low-Lying Residual Adenocarcinoma After Total Neoadjuvant Therapy to Improve Organ Preservation Rates

Recruiting now · Phase 2

Conditions studied: Rectal Adenocarcinoma, Rectal Cancer

In brief

Rectal cancer patients who do not achieve a complete response to standard of care chemotherapy and radiation often require surgical resection as part of curative intent therapy. This study will evaluate whether additional "focal" radiation delivered internally (rectal brachytherapy) can provide complete responses and thus spare the requirement for surgery. The main questions are whether: 1) rectal brachytherapy is safe in this clinical treatment paradigm and if 2) rectal brachytherapy improves organ preservation (no need for surgery). The trial involves an additional MRI pelvis and sigmoidoscopy with marker placement to define high-risk residual disease for radiation planning. Subsequently, 3 outpatient brachytherapy treatments are given on a weekly basis. If a patient achieves a complete response to brachytherapy, standard of care non-operative surveillance visits are conducted with study visits aligned during the first two years following brachytherapy.

Key facts

Study ID

NCT07292298

Run by

University of Colorado, Denver

People needed

44

Starts

2026-11-01

Expected to finish

2031-11-01

Last updated by the study team

2026-04-06

Who can join

Age: 18 and older, up to 100. Sex: any. Healthy volunteers: not accepted.

You may qualify if…

• Provision to sign and date the consent form.
• Stated willingness to comply with all study procedures and be available for the duration of the study.
• Adults (18-100 years old)
• ECOG 0-3
• Patients with MMR-proficient low-mid rectal adenocarcinoma cT1-4 N0-2 M0 who underwent total neoadjuvant therapy who have not achieved complete response (i.e. incomplete or near-complete) in the rectal primary tumor such that surgical resection, if offered presently or in the future, would be an APR or low LAR per colorectal surgeon expert opinion and central review at University of Colorado rectal tumor board. Tumor restaging will be 4-16 weeks following completion of total neoadjuvant therapy, and no sooner than 8 weeks if patients received chemotherapy followed by chemoradiation/short course radiation.
• Residual rectal disease must have its craniocaudal extent <4 cm with thickness <1.2 cm. Tumor must have <50% circumferential involvement. Residual disease must be above the dentate line and not involving the anal canal.
• In patients with original cN1-2 disease, restaging CT and MRI after total neoadjuvant therapy must demonstrate at least near-complete response of the pelvic lymph nodes per NCCN criteria as evaluated by central review at University of Colorado rectal tumor board.
• Interval of time between completion of TNT and initiation of rectal brachytherapy must be between 4-16 weeks.
• Patients must be recovered from total neoadjuvant therapy and must not have significant rectal incontinence at time of screening.
• Received conventionally fractionated external beam chemoradiation between 45-56 Gy or short-course external beam radiation prescription of 25 Gy to rectal mucosa, in addition to systemic chemotherapy before or after radiation per National Comprehensive Cancer Network (NCCN) guidelines.
• Women of child-bearing potential must have a negative urine or serum pregnancy test within 14 days of HDR treatment.
• Men and women of reproductive potential who are sexually active must agree to follow instructions of contraception for the duration of the study and 6 months post-rectal brachytherapy completion.
• CBC at the time of screening must have platelets>50 10\^9/L, Hemoglobin>8 g/dL and Absolute Neutrophil Count > 500 10\^9/L

You may not qualify if…

• History of ulcerative colitis or Crohn's disease.
• Pelvic radiotherapy given prior to rectal cancer external beam radiation.
• Prior colorectal surgery in which anastomotic site is at or near HDR brachytherapy target.
• o Prior local excision is not an exclusion criterion.
• Uncontrolled intercurrent severe illness, including but not limited to, ongoing or active infection, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina pectoris, cardiac arrhythmia, interstitial lung disease, serious chronic gastrointestinal conditions associated with diarrhea, or psychiatric illness/social situations that would limit compliance with study requirement, substantially increase risk of incurring AEs or compromise the ability of the patient to give written informed consent.
• Life expectancy <3 years per provider discretion.
• Concurrent administration of any cytotoxic chemotherapy, immunotherapy, or other any targeted oncologic agent that would impact rectal cancer is not allowed during study protocol.
• If rectal cancer has been treated outside of standard total neoadjuvant therapy per NCCN guidelines, patients are ineligible for the trial. This includes if patients received external beam chemoradiation dose with prescription >56 Gy or short-course radiation to rectal mucosa prescription >30 Gy.
• Pregnant women.

Where it is running

• University of Colorado Cancer Center — Aurora, Colorado, United States (enrolling)
• University of Rochester Medical Center — Rochester, New York, United States
• Oregon Health and Sciences University — Portland, Oregon, United States

Full record on ClinicalTrials.gov

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