Evaluating the TLI-ATG conditioning regimen before allogeneic stem cell transplantation in patients with lymphoma or leukemia

This study evaluated the safety and effectiveness of total lymphoid irradiation and anti-thymocyte globulin (TLI-ATG) conditioning before stem cell transplantation (SCT) in patients with lymphoma or leukemia. This study concluded that this regimen was well-tolerated and effective, especially for patients who had multiple lines of prior treatment.

Allogeneic stem cell transplantation (alloSCT) is one type of stem cell transplant. This procedure involves collecting healthy stem cells from a donor. Then, the healthy stem cells are introduced into the patient. A conditioning regimen is given first to the patient to get rid of any remaining cancer cells. This regimen typically involves high-dose chemotherapy. However, many patients are not good candidates for intensive conditioning regimens. This can be due to other existing medical conditions or age. 

TLI-ATG is a new conditioning regimen that is less intense than conventional regimens. It combines radiation therapy with antibody therapy to get rid of cancer cells and prevent a complication called graft-versus-host disease (GVHD). GVHD occurs when the donated stem cells attack the patient’s healthy cells. It can be short-term (acute) or last a long time (chronic). The long-term outcomes for patients treated with TLI-ATG before alloSCT remain under investigation.

This study had 612 patients with lymphoma or leukemia who underwent alloSCT. Patients were followed-up for an average of 6 years. One-third of the included patients had at least 3 other medical conditions (comorbidities). 56% of patients received an alloSCT from an unrelated donor. 

Overall, 98% of all patients underwent alloSCT. 43% of patients were hospitalized within 100 days of the transplant. These were due to infection (20%) or low white blood cell count with fever (15%). 3% (16 patients) were hospitalized for short-term GVHD. 95% of all patients had successful engraftment (donated stem cells travel through the blood of the patients and begin making new healthy cells). 

1 year later, the rate of mortality (death) not caused by a relapse was 9% of all patients. 1 year later, 14% of patients had short-term GVHD, and 22% of patients had long-lasting GVHD. 

Of 193 patients who had acute myeloid leukemia (AML), 76% had no signs of cancer after the transplant. 42% of patients were still alive 4 years later, and 32% did not have tumor growth or spread. However, 62% of patients had the cancer come back less than 6 months after the transplant.

In patients with chronic lymphocytic leukemia (CLL; 80 patients), 21% had no signs of cancer remaining (complete response). 73% had a partial response after the SCT. The 4-year survival was 63% and the survival without cancer growing or spreading after 4 years was 43%. The average survival for patients with CLL was 7.8 years after alloSCT.

This study concluded that TLI-ATG conditioning was effective and well-tolerated for patients with lymphoma or leukemia. The authors suggest that this regimen was particularly effective for patients who had multiple lines of prior treatment.

The TLI-ATG conditioning regimen was associated with a high risk of relapse. Treatment approaches to reduce this risk remain under investigation.