This study aims to observe and explore the efficacy and safety of Rituximab-Methotrexate-Temozolomide-Thiotepa (RMTT) regimen as first-line therapy for primary central nervous system diffuse large B-cell lymphomas(PCNS DLBCL)

Inclusion Criteria:

• Patients voluntarily joined the study, signed the informed consent, and had good compliance;
• Patients with 18 Years to 75 Years(at the time of signing the informed consent); Eastern Cooperative Oncology Group Performance Status (ECOG-PS) score: 0-3;
• Patients with histopathologically confirmed newly diagnosed primary central nervous system diffuse large B-cell lymphoma, and there were intracranial evaluable lesions (long diameter greater than 1.5cm, short diameter greater than 1cm);
• Patients who have not received any systemic therapy, except those who use hormones to control complications
• Expected survival of more than 3 months.
• Female patients of reproductive age should agree that birth control (such as intrauterine device, birth control pills, or condoms) must be used during the study period and for six months after completion; Having a negative serum pregnancy test within 7 days prior to study enrollment, and must be non-lactating; Male patients should agree to use contraception during the study period and for six months after the end of the study.

Exclusion Criteria:

• Patients who have previously received antitumor therapy or targeted therapy
• Patients who have undergone major surgery within the past 3 weeks .
• Presence of severe or uncontrolled comorbid conditions including, but not limited to, symptomatic congestive heart failure, uncontrolled hypertension, unstable angina, active peptic ulcer disease, or severe hemorrhagic disorders such as hemophilia A, hemophilia B, von Willebrand disease, or history of spontaneous bleeding requiring transfusion or other medical interventions.
• Any active infection requiring systemic antimicrobial therapy within 14 days before starting study treatment, including, but not limited to, bacterial, fungal, and viral infections.
• Patients who are pregnant or breastfeeding.
• Current participation in other clinical studies, or initiation of study drugs administration less than 4 weeks after completion of previous clinical study treatment.
• Patients with concomitant diseases that, in the investigator's judgment, may seriously endanger patients' safety or may interfere with the completion of the study, or are deemed unsuitable for inclusion for other reasons.