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NCT Number: NCT07068763

Node-Sparing Short-Course Radiation Combined With Capecitabine and PD-1/CTLA-4 for MSS Early Rectal Cancer

This is a single-arm, prospective, multicenter study evaluating a novel neoadjuvant treatment strategy for patients with early, mid-low rectal adenocarcinoma that is microsatellite stable (MSS). Instead of irradiating regional lymph nodes, we deliver short-course radiotherapy (25 Gy in 5 fractions) exclusively to the primary tumor ("lymph-node-sparing" approach), immediately followed by four 3-week cycles of capecitabine plus combined PD-1/CTLA-4 immune checkpoint inhibitors. Two weeks after completing chemo-immunotherapy, tumor response is assessed. Patients who achieve a clinical complete response may enter a "watch-and-wait" program; others will undergo local excision or total mesorectal excision (TME) as appropriate. The primary endpoint is the rate of complete response (clinical and pathological). Secondary endpoints include organ-preservation rate, 3-year local recurrence, 3-year disease-free and overall survival, toxicity, and quality-of-life measures. Results from a pilot study suggest that this regimen may substantially improve complete response rates while reducing radiation-related toxicity, potentially allowing more patients to avoid radical surgery and permanent stoma.

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Key information

Conditions

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

Age range

18 year–80 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Primary location

Who can participate

Healthy volunteers accepted: No

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

Inclusion criteria

  • Patients who have a strong willingness to preserve the anus and are willing to receive neoadjuvant therapy.
  • Male or Female aged 18-80.
  • Patients diagnosed with low rectal cancer within 7 cm from the lower edge of the tumor to the anal verge by pelvic MRI and rectal ultrasound, the clinical stage is cT2-3N0M0.
  • Histologically confirmed rectal adenocarcinoma; Genetic testing suggests MSI-L or MSS, or tumor biopsy immunohistochemistry reveals pMMR, that is, MSH1, MSH2, MSH6, and PMS2 are all positive.
  • Eastern Cooperative Oncology Group (ECOG) score 0-1.
  • No previous treatment (including anti-tumor therapy, immunotherapy or pelvic radiation).
  • Informed consent form signed.

Exclusion criteria

  • Patients with a previous history of malignant tumors besides rectal cancer.
  • Patients with distant metastases before enrollment.
  • Patients with metastatic regional or non-regional lymph nodes are assessed by MRI or CT.
  • Patients with obstruction, perforation, or bleeding that require emergency surgery.
  • Patients with severe concomitant diseases and estimated survival time ≤ 5 years.
  • Allergic to any component of the therapy.
  • Patients who received immunosuppressive or systemic hormone therapy for immunosuppressive purposes within 1 month prior to the initiation of therapy.
  • Contraindications to radiotherapy and chemotherapy.
  • Patients who have received any other experimental drug (including immunotherapy) or participated in another interventional clinical trial within 30 days before screening.
  • Factors leading to study termination, such as alcoholism, drug abuse, other serious illnesses (including psychiatric disorders) requiring combination therapy, and patients with severe laboratory abnormalities. Patients with congenital or acquired immune deficiency (such as HIV infection).
  • Vulnerable groups, including mentally ill, cognitively impaired, critically ill patients, minors, pregnant or lactating women, illiterate, etc.

Other conditions that investigators consider not suitable for this study.

  • Patient not suitable for participating by other concerns of researchers.

Treatment and study plan

Lymph-node-sparing short-course radiotherapy

Radiation

Three-dimensional conformal or intensity-modulated radiotherapy targeting only the primary tumor bed (no regional lymph nodes), delivering a total dose of 25 Gy in 5 Gy fractions over five consecutive days.

Capecitabine

Drug

Oral capecitabine 1,000 mg/m² administered twice daily on Days 1-14 of each 21-day cycle, for a total of four cycles.

PD-1/CTLA-4 inhibitor (Aiparolitoworixureli injection)

Drug

Intravenous PD-1/CTLA-4 bispecific monoclonal antibody at 5 mg/kg every 3 weeks for four cycles, starting on Day 8 after completion of radiotherapy.

Primary outcomes

  1. Clinical and pathological complete response rate (CR rate)

    Time frame: Up to 12 weeks after completion of chemo-immunotherapy

    Proportion of enrolled patients who achieve a clinical complete response (cCR) on imaging, endoscopy, and biopsy and/or a pathological complete response (pCR) in surgical specimens (if resected) following lymph-node-sparing short-course radiotherapy combined with capecitabine and PD-1/CTLA-4 inhibitor.

Secondary outcomes

  1. Organ preservation rate

    Time frame: 1 year after enrollment

    Proportion of patients who avoid total mesorectal excision (TME) and permanent stoma by remaining in watch-and-wait or undergoing only local excision.

  2. 3-year local recurrence rate

    Time frame: 3 years

    Proportion with tumor recurrence in the pelvis

  3. Overall survival(OS）

    Time frame: 3 years after chemotherapy or surgery

    The three-year overall survival of patients.

  4. Adverse effects rate

    Time frame: From date of initiation of treatment until the date of death from any cause, assessed up to 3 years

    Rate of radiotherapy, chemotherapy and immunotherapy related adverse events

Study contacts

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

Bingjun Bai, MD

CONTACT

[email protected]

8613858816897

Sponsors and collaborators

Lead sponsor

Sir Run Run Shaw Hospital

Other

Registry information

Official study title

Node-Sparing Short-Course Radiation Combined With Capecitabine and PD-1/CTLA-4 for MSS Early Middle and Low Rectal Cancer (mRCAT-E): An Open-label, Single-arm, Prospective Multicenter Clinical Trial

Acronym: mRCAT-E

Important dates

Study start
2025
Primary completion
2026
Study completion
2029
First posted
Jul 16, 2025
Registry last updated
Jan 6, 2026

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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