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

NCT07292298 | Recruiting Phase 2 DMC

• 1 other identifier: 25-1202.cc
• Study Type: interventional
• Target: 44
• Locations: 1 country
• Sites: 3

Brief Summary

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.

Conditions

Rectal Adenocarcinoma; Rectal Cancer

Keywords

Locally Advanced Rectal Cancer; Non-metastatic Rectal Cancer; Rectal Neoplasms

Outcome Measures

Primary Outcomes (1)

• Organ preservation (no surgical requirement) of the rectum associated with complete clinical response

  As evaluated by standard of care sigmoidoscopy and MRI

  2 years following study treatment

Secondary Outcomes (4)

• Locoregional recurrence free survival

  2 years following study treatment

• Distant metastatic free survivial

  2 years following study treatment

• Overall survival

  2 years following study treatment

• Bowel function

  2 years following study treatment

Study Arms (1)

HDR Rectal Brachytherapy Boost

EXPERIMENTAL

The intervention consists of a boost using Iridium-192 delivered via an intracavitary applicator in three weekly fractions totaling 21 Gy. The goal is to improve organ preservation rates and avoid surgical resection (APR or low LAR). Treatment planning includes MRI, endoscopic clip placement, and CT simulation prior to each fraction.

Radiation: High Rare Dose Rectal Brachytherapy Boost

Interventions

High Rare Dose Rectal Brachytherapy Boost RADIATION

HDR rectal brachytherapy boost using Iridium-192 delivered via an intracavitary applicator in three weekly fractions (total dose: 21 Gy) for patients with low-lying residual rectal adenocarcinoma following total neoadjuvant therapy.

HDR Rectal Brachytherapy Boost

Eligibility Criteria

• Age: 18 Years - 100 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

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.
• 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.

Sponsors & Collaborators

• University of Colorado, Denver: lead
• Cancer League of Colorado: collaborator

Study Sites (3)

University of Colorado Cancer Center

Aurora, Colorado, 80045, United States

RECRUITING

University of Rochester Medical Center

Rochester, New York, 14642, United States

RECRUITING

Oregon Health and Sciences University

Portland, Oregon, 97239, United States

RECRUITING

MeSH Terms

Conditions

Rectal Neoplasms

Condition Hierarchy (Ancestors)

Colorectal Neoplasms; Intestinal Neoplasms; Gastrointestinal Neoplasms; Digestive System Neoplasms; Neoplasms by Site; Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Intestinal Diseases; Rectal Diseases

Study Officials

• David Binder

  University of Colorado, Denver

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Robyn Swing

CONTACT

720-848-0607; robyn.swing@cuanschutz.edu

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: December 5, 2025
• First Posted: December 18, 2025
• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): November 1, 2030
• Study Completion (Estimated): November 1, 2031
• Last Updated: February 19, 2026

Record last verified: 2026-02

Locations

US (3)