Whole Body PET-CT In Management Of Lymphoblastic Lymphomas In Adults: Does It Have a Prognostic Impact?

The two relevant questions that emerge and remains unanswered in the management of adult lymphoblastic lymphomas (LBL) are- how to select patients for mediastinal radiation and whom to subject for autologous transplant. Mediastinal radiation or intensification of therapy may reduce the mediastinal recurrence- a common site for relapse. It is also understood that not all patients with residual mediastinal mass relapse. The inability of computed tomography to differentiate between necrotic and viable disease in a residual mediastinal mass post induction therapy led us to explore PET-CT as modality to differentiate the same. In a retrospective analysis we evaluated the role of post-induction chemotherapy PET-CT in predicting the risk of relapse or progression in adult LBL patients.

In a single centre retrospective analysis we included newly diagnosed LBL patients (>15 years) who were treated with ALL- like therapy between January 2010 and February 2013. All patients who underwent PET-CT after induction chemotherapy were analysed. SUVmax was used to assess the response. Details of demographic variables, diagnosis, subtype, baseline LDH, bone marrow involvement, cerebrospinal fluid analysis, chemotherapy, radiotherapy, responses, relapse/progression, death and its cause and last follow up date were taken from electronic medical records.

Twenty-two patients (17 males and 5 females) with median age 24.5 years (range, 16-44 years) were analysed. All patients had T- LBL. Thirteen patients (13/22) had stage IV disease (Ann Arbor stage) and all had bulky mediastinal mass at diagnosis. None of the patient had CSF or bone marrow involvement. Raised LDH and low albumin were present in 80% and 60% of patients respectively. Median WBC was 10,200/cumm (range, 4400-15300/cumm). All but 4 patients received BFM-90 ALL protocol based therapy. After induction 19 patients achieved complete remission on PET-CT. Patients who had residual mediastinal masses on PET-CT relapsed during later phase of therapy (all within 6 months) in mediastinum and died subsequently. Mediastinal radiation was given to one of these patients but it did not prevent a subsequent relapse. One patient who achieved complete response had bone marrow relapse after 16 months of therapy. Three patients had treatment related death (sepsis). At median follow up of 14 months 1-year overall survival was 69% and progression free survival was 78%.

Post induction therapy PET-CT seems to have prognostic role and may predict relapse for patients with residual disease activity. Such patients should be considered for treatment intensification. However, the role and timing of mediastinal radiation in such patients remains investigational.

No relevant conflicts of interest to declare.