The Role of Interim F-18 FDG PET/CT in Patients of T Lymphoblastic Leukemia/Lymphoma Treated with ALL-Type Regimens

Background:

T lymphoblastic leukemia/lymphoma (T-LBL) is highly aggressive. Although intensive chemotherapies such as acute lymphoblastic leukemia (ALL)-type regimens are commonly used, about half adult patients eventually relapse and die of T-LBL. Overwhelming evidences have confirmed the role of interim F-18 FDG PET/CT in Hodgkin lymphoma and many ongoing studies have implemented risk-adapted strategy determined by interim FDG-PET/CT. However, the role of interim FDG-PET/CT in T-LBL remains unclear.

Materials and methods:

47 adult patients of T-LBL treated with ALL-like regimens were retrospectively reviewed. They were treated with modified Berlin-Frankfurt-Münster (BFM)-90 regimen (n=27), Medical Research Council (MRC) UKALLXII/Eastern Cooperative Oncology Group (ECOG) 2993 regimen (n=5), hyperCVAD/MA regimen (n=12), or other unspecified regimens (n=3). Interim (defined as the period between induction therapy and re-induction therapy) FDG-PET/CT was done in all 47 patients and evaluated according to the International Harmonization Project (IHP) criteria.

Results:

The male to female ratio was 3:1, and 29.8% of patients were older than 30 years old. About 90% of patients had mediastinal mass at presentation and 53.2% had bone marrow infiltration. 85.1% of patients had advanced disease. After induction therapy, interim FDG-PET/CT was positive in 19 patients (40.4%), most of whom had residual disease in the mediastinal lesion. Subsequent treatments were not changed according to this interim PET/CT results. After a median follow up time of 28 months, the 2-year and 3-year progression free survival (PFS) rate were 39% and 30%, respectively, and the 2-year and 3-year overall survival (OS) rate were 54% and 45%, respectively. Using Kaplan-Meier survival analysis and log-rank test, it was found that interim FDG-PET/CT positivity correlated with significantly inferior PFS and OS (p=0.002 and 0.010, respectively). Furthermore, patients with higher age (>30) had inferior PFS and OS than younger patients (p=0.037 and 0.036, respectively). However, there were no significant relationship between PFS, OS and bone marrow infiltration, LDH level, and stages (p>0.05).

Conclusions:

Interim FDG-PET/CT may predict PFS and OS in adult patients of T-LBL treated with ALL-type regimens, which needs to be validated in prospective clinical trials. The optimal criteria for interim FDG-PET/CT evaluation and risk-adapted treatment strategy determined by interim FDG-PET/CT should be investigated in future clinical practice.