This study is a prospective, single center, phase II clinical study involving 108 patients with primary and late stage Diffuse Large B-cell Lymphoma complicated by large masses and extranodal involvement. The study aims to evaluate the efficacy of radiotherapy targeting large masses and extranodal involvement in treatment-naïve advanced DLBCL patients with large mass lesions and/or extranodal involvement after they had initially been treated with standard immunochemotherapy and received complete remission as assessed by PET-CT.

After completing the standard immunochemotherapy, subjects will be randomly divided into the radiotherapy group or the non-radiotherapy group, and the curative effects will be evaluated every three months after the end of the treatment or after their leaving the group, so as to obtain the relevant data and data of the 2-year Progression Free Survival, survival of the subjects and Treatment-related side effects.

Safety analysis:

The safety analysis is mainly based on descriptive statistical analysis, which lists and describes the incidence, severity, correlation, risk and outcome of adverse events (AE) in this trial.

Efficacy analysis:

The Kaplan-Meier method will be used to draw the overall survival curve and the progression-free survival curve, and to estimate the median survival time, median progression-free survival period and their 95% confidence intervals.

Before starting the study, patients must read and sign the current version of informed consent form approved by the Ethics Committee (EC). All research steps must be carried out within the time window specified in the research schedule.

The duration of safety data collection is from the patient signing the Informed Consent Form (ICF) to the end of the study, with all AEs recorded in the CRF.

The severity of AE will be evaluated based on the NCI CTCAE 5.0 standard. Each patient will undergo a series of planned visits and specific data will be recorded at different time points during the scheduled visits. All examinations/tests are recommended, and the exact examination/test items to be completed during the study shall be subject to clinical practice.

Investigators must be physicians who have been trained in terms of knowledge and conduct of clinical trials and work under the guidance of senior professionals; Prior to the start of the trial, the clinical ward must be inspected so as to ensure its compliance with standardized requirements and to ensure complete readiness of rescue equipment. It is recommended that professional nursing staff administer medication to the subjects and have a detailed understanding of the medication usage to ensure patient compliance; Each investigation site must strictly follow the study protocol; All participating sites should adhere to the ICH-GCP regulations and standard operating procedures (SOPs) for preservation, and all clinical trial information should be recorded, disposed of, and saved for purposes of accurate reporting, interpretation, and verification of study results; Confirm that all data records and reports are correct and complete, and save the original and essential documents related to the study.

This clinical study will be conducted in accordance with the principles established by the 18th World Federation of Medical Associations (Helsinki, 1964) and all subsequent revisions. Before enrollment, it is necessary to weigh the foreseeable risks and inconveniences that study may bring to the subjects against the potential benefits for enrolled patients. Clinical trials can only be initiated and continued when the expected benefits outweigh the risks. Prior to participating in clinical trials, each subject should provide voluntary informed consent, otherwise they cannot be screened or selected.

Inclusion Criteria:

1. Using the World Health Organization (WHO) classification of diseases, newly diagnosed diffuse large B-cell lymphoma with large masses (tumor diameter ≥ 7.5cm) and or extranodal involvement patients diagnosed by histology

2. Age: no limit, male or female;

3. ECOG score: 0-2

4. The laboratory meets the following requirements:

   4.1 The bone marrow hematopoietic function is basically normal: WBC ≥ 3.5×10^9/L, ANC ≥ 1.0×10^9/L, PLT ≥ 75 ×10^9/L, Hb ≥ 80g/L;

   4.2 Liver function: AST/ALT≤2×ULN, TBILI≤2×ULN;

   4.3 Renal Function : creatinine clearance rate(Ccr) ≥50ml/min

5. Non-menopausal or non-surgical sterilization female patients of childbearing age must have a serum pregnancy test within 3 days before the first medication, and the result is negative; and they must be non-lactating. Female patients of childbearing age or male patients whose partners are women of childbearing age must agree to use highly effective methods of contraception during the study and within 6 months after the last administration of the study drug;

6. Expected survival period ≥ 6 months;

7. The patient voluntarily joined the study and signed the informed consent;

Exclusion Criteria:

1. Serum pregnancy test positive or breastfeeding women;

2. Lymphoma patients with central nervous system (CNS) invasion;

3. Clinically significant heart disease, including unstable angina, acute myocardial infarction 6 months before randomization, congestive heart failure (NYHA), cardiac function class III or IV; or cardiac left ventricular ejection fraction <50%;

4. Patients with ≥2 grade neuropathy;

5. Patients with active hepatitis B (HBV), hepatitis C (HCV), and other acquired and congenital immunodeficiency diseases;

6. Patients with severe active infection who require systemic antibiotic treatment;

7. Have a history of serious neurological or psychiatric diseases, unable to participate in the trial normally, including dementia, epilepsy, severe depression and mania, etc.;

8. Drug abuse, medical, psychological or social conditions that may interfere with the subject's participation in the research or the evaluation of the research results;

9. Patients considered by the investigator to be unsuitable for enrollment;

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