Low-dose radiotherapy with pucotenlimab and CAPEOX for pMMR locally advanced rectal cancer

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This randomized, open-label phase II trial enrolls patients with pMMR/MSS locally advanced rectal adenocarcinoma and randomizes them 1:1 to receive a single fraction of either 2 Gy or 5 Gy low-dose radiotherapy followed by pucotenlimab 200 mg IV every 3 weeks plus CAPEOX chemotherapy. Treatment response is assessed after two cycles using endoscopy and pelvic MRI to guide whether patients continue systemic therapy, switch to standard chemoradiotherapy, or receive alternative multidisciplinary care. The trial measures safety and tumor response as neoadjuvant outcomes, with subsequent surgical or organ-preserving decisions made according to response. All treatments and follow-up are performed at the sponsoring center with monitoring for adverse events and radiographic/clinical outcomes.

Why it matters

Who can join: the full rules

Inclusion Criteria

* Written informed consent provided prior to any study-specific procedures.
* Age 18 to 75 years at the time of enrollment.
* Histologically confirmed rectal adenocarcinoma.
* Tumor located within 10 cm from the anal verge, as assessed by endoscopy or imaging.
* Locally advanced disease, defined as clinical stage T2N+ or T3-T4a (any N) based on pelvic magnetic resonance imaging (MRI).
* Proficient mismatch repair (pMMR) or microsatellite-stable (MSS) tumor status confirmed by immunohistochemistry or molecular testing.
* No evidence of distant metastasis on preoperative imaging, including chest, abdominal, and pelvic computed tomography (CT).
* Eastern Cooperative Oncology Group (ECOG) performance status 0-1.
* Adequate organ function as defined by:
* Absolute neutrophil count ≥1.5 × 10⁹/L
* Platelet count ≥100 × 10⁹/L
* Hemoglobin ≥90 g/L
* Total bilirubin ≤1.5 × upper limit of normal (ULN)
* Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × ULN
* Creatinine clearance ≥50 mL/min
* Thyroid-stimulating hormone (TSH) within normal limits
* Women of childbearing potential must have a negative pregnancy test and agree to use effective contraception during the study and for a protocol-defined period after the last dose.
* Men with partners of childbearing potential must agree to use effective contraception during the study and for a protocol-defined period after the last dose.

Exclusion Criteria

* Clinical T4b disease, defined as tumor invasion into adjacent organs or structures on baseline imaging.
* Evidence of distant metastasis outside the pelvis.
* Prior pelvic or abdominal radiotherapy.
* Prior treatment with immune checkpoint inhibitors or other systemic anticancer therapy for rectal cancer.
* Active or history of autoimmune disease requiring systemic treatment, except for conditions considered low risk for recurrence (e.g., vitiligo, resolved childhood asthma).
* Ongoing use of systemic immunosuppressive therapy, including corticosteroids equivalent to \>10 mg/day of prednisone, within 2 weeks prior to enrollment.
* Known human immunodeficiency virus (HIV) infection.
* Active hepatitis B virus infection with positive hepatitis B surface antigen and high viral load, or hepatitis C virus infection requiring treatment.
* Uncontrolled active infection or other serious medical condition that, in the investigator's judgment, would compromise patient safety or study compliance.
* History of another malignancy within 5 years, except for adequately treated basal cell carcinoma of the skin, cervical carcinoma in situ, or other malignancies with negligible risk of recurrence.
* Known hypersensitivity or allergy to pucotenlimab, oxaliplatin, capecitabine, or any of their excipients.
* Pregnant or breastfeeding women.
* Any condition that, in the investigator's opinion, makes the participant unsuitable for study participation.

Where it's running

• Dept. of Colorectal Surgery, Sun Yat-sen University Cancer Center. Yuexiu District, Dongfeng East Road 651
  Guangzhou, Guanggong, China Recruiting

Study contacts

• Principal investigator: Pei-Rong Ding — Sun Yat-Sen University Cancer Center
• Study coordinator: Wu Jiang
• Email: jiangwu@sysucc.org.cn
• Phone: +86-15989120166

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.