The goal of this single-arm, prospective study is to learn if high dose gemcitabine, busulfan and thiotepa with autologous stem cell transplantation to treat primary or relapse central nervous system lymphomas. It will learn about the safety and efficacy of combination therapy. The main question it aims to answer is:

Efficacy and safety of the combination of high dose gemcitabine, busulfan and thiotepa as a bridging therapy to ASCT in patients with CNSL.

Participants will:

Take gemcitabine (2.5 g/m²) was administered intravenously (IV) on Days -9 and -3, Busulfan (3.2 mg/kg) was given IV over 3 hours on Days -9 to -7, and thiotepa (5 mg/kg) was administered IV on Days -5, -4, and -3. Peripheral stem cells were infused on Day 0.

Visit the clinic for checkups and tests in accordance with the International Primary CNS Lymphoma Group (IPCG).

Researchers will observe the patients receiving GemBuTT regimen as conditioning therapy in CNSL.

Inclusion Criteria:

1. age between 18 and 70 years;
2. CNS status of complete remission (CR) or partial response (PR) as assessed by magnetic resonance imaging (MRI), positron emission tomography-computed tomography (PET/CT), or CSF analysis (if applicable);
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0,1 or 2;
4. absence of systemic lymphoma in the neck, chest, abdomen, and pelvis as assessed by CT and bone marrow biopsy;
5. negative HIV and hepatitis virus infections (particularly hepatitis B or C, with HBV DNA ≥ 10,000 copies/mL);
6. left ventricular ejection fraction (LVEF) ≥50% and no uncontrolled arrythmias or symptomatic cardiac disease;
7. forced expiratory volume in one second (FEV1) ≥70%;
8. serum creatinine clearance ≥ 50 ml/min and/or serum creatinine ≤ 1.8 mg/dL;
9. serum bilirubin ≤ 2 times the upper limit of normal, serum glutamate oxaloacetate transaminase (SGOT) and/or serum glutamate pyruvate transaminase (SGPT) ≤ 3 times the upper limit of normal.

Exclusion Criteria:

1. relapse after stem cell transplantation;
2. other uncontrolled malignancies;
3. immunodeficiency;
4. active infection requiring parenteral antibiotics;
5. pregnant or lactation;
6. severe psychiatric or psychological conditions.