Short-course Radiotherapy or Long-course Chemoradiation Followed by MFOLFOXIRI Consolidation Chemotherapy for Organ Preservation in Low Rectal Cancer

Given the growing focus on preserving organ function and the utilization of neoadjuvant therapy, it is important to investigate and enhance the application of comprehensive neoadjuvant therapy in low rectal cancer. This approach aims to minimize or circumvent the organ dysfunction and subsequent decline in quality of life associated with radical surgery, with improving disease-free survival (DFS), while . Consequently, we propose to initiate a multicenter clinical trial to examine the medium- and long-term effectiveness of complete neoadjuvant therapy (comprising either short-course radiotherapy or long-course chemoradiation, followed by consolidation chemotherapy with mFOLFOXIRI) in increasing organ preservation rates in patients with low rectal cancer.

This randomised, open-label, multicentre,phase II trial began in December, 2022, as a neoadjuvant trial about short-course radiotherapy or long-course chemoradiation followed by mFOLFOXIRI consolidation chemotherapy,in patients aged 18 years to 70 with clinical stage II-III locally advanced low rectal cancer from six Chinese institutions. The primary endpoint of the study was the 1-year organ preservation rate, with a comparison to historical data. Additionally, the study compared the differences between two radiotherapy regimens within the TNT treatment and explored biomarkers to predict tumor response

Patients with local advanced rectal cancer (cT2-4aN0-2,M0, 8cm from the anus verge) were recruited. Patients receive short-course radiotherapy (25Gy/5 times) followed by consolidation chemotherapy or long-course chemoradiation (50Gy/25 times;capecitabine 825 mg/m² twice daily) with mFOLFOXIRI (Irinotecan 150 mg/m2 iv gtt (2h) d1, Oxaliplatin 85 mg/m2 iv gtt (2h) d1, Calcium folinate 400 mg/m2 iv gtt (2h) d1, Total amount of fluorouracil 2400 mg/m2 iv gtt (48h)), treatment repeats every 14 days for 8 courses in the absence of disease progression or unacceptable toxicity. The efficacy evaluation occurs after the fourth and eighth chemotherapy cycle. Patients showing a complete response (CR), partial response (PR), or stable disease (SD) with reduction or stability in tumor size are advised to continue and complete all planned consolidation chemotherapy. However, if the evaluation indicates stable disease with an increase (SD increased) or progressive disease (PD), and if an R0 resection (complete removal of the tumor with no cancer cells at the margins) is feasible, radical total mesorectal excision (TME) should be pursued. In cases where R0 resection is not achievable, the treatment should align with the guidelines for managing unresectable rectal cancer. Upon the final efficacy assessment after the eighth chemotherapy cycle, several pathways are considered based on the outcomes: patients achieving a clinical complete response (cCR) may proceed to a Watch \& Wait approach. Those with a near clinical complete response (near cCR) undergo local transanal resection. If the patient's condition is evaluated as PR/SD with a reduction but does not qualify as near cCR, radical TME is recommended. For patients showing SD with an increase or PD, yet with a potential for R0 resection, radical TME is again the suggested course of action. If R0 resection is unattainable, treatment should adhere to the guidelines for unresectable rectal cancer.

Eligibility Criteria:
Inclusion Criteria:

Diagnosis: Histologically confirmed rectal adenocarcinoma. Preoperative Staging: Clinical stages cT2-4aN0-2. Tumor Location: Tumor's lower edge within 8cm from the anus, potentially affecting anal preservation or function.

Metastasis Screening: Preoperative chest, abdomen, and pelvis CT to rule out distant metastasis.

Biomarkers: Positive expression of pMMR (MSH1/MSH2/MSH6/PMS2) on tumor biopsy immunohistochemistry.

Staging Methods: Combination of thoracic and abdominal pelvic CT, pelvic MRI, and endoscopic or transrectal ultrasound.

Patient Characteristics Age: 18 to 70 years. Performance Status: ECOG score of 0-1. Life Expectancy: At least 2 years. Blood Counts: WBC \>4000/mm\^3, PLT \>100,000/mm\^3, Hb \>10g/dL (chronic anemia with Hb \< 10.0g/dL subject to multidisciplinary team review).

Liver Function: Serum total bilirubin ≤1.5×ULN (≤3×ULN for Gilbert syndrome); AST and ALT ≤2.5×ULN.

Renal Function: Serum creatinine ≤1.5×ULN or creatinine clearance \>50 mL/min. Other Criteria: Non-pregnant, not nursing, no other malignancies (except non-melanoma skin cancer or cervical carcinoma in situ) within the past 5 years, capable of providing informed consent, no severe comorbidities affecting survival.

Prior Treatment No prior surgery, chemotherapy, or radiotherapy for rectal cancer. No prior biological therapy. No restrictions on previous endocrine therapy.

Exclusion Criteria:

Informed Consent: Lack of signed informed consent. Genetic Markers: Tumor biopsy indicating dMMR or MSI-H detected. Advanced Tumor Stage: Preoperative assessment showing tumor invasion of surrounding tissues/organs (T4b).

Obstruction: Unresolved colonic obstruction; presence of tumor perforation. Metastasis: Evidence of preoperative distant metastasis. Cardiac Conditions: Arrhythmia requiring antiarrhythmic therapy (excluding beta-blockers or digoxin), symptomatic coronary artery disease or recent myocardial ischemia (within 6 months), or congestive heart failure above NYHA Grade II.

Hypertension: Severe, poorly controlled hypertension. Infections: HIV infection, active chronic hepatitis B or C, other serious infections; active tuberculosis or anti-TB therapy within the past year.

Organ Function: Poor fluid quality, organ function decompensation. Previous Treatment: History of pelvic or abdominal radiotherapy; multiple primary colorectal cancers.

Neurological Conditions: Seizures requiring management (e.g., steroids, antiepileptic therapy).

Cancer History: Other malignant tumors within the past 5 years, excluding cured cervical carcinoma in situ or basal cell carcinoma of the skin.

Substance Abuse: Substance abuse or medical, psychological, or social conditions affecting study participation or result evaluation.

Allergies: Known or suspected allergy to study drugs or related medications. Stability: Any unstable condition that may compromise safety or compliance. Reproductive Status: Pregnant or lactating women, or fertile women not using effective contraception.