PB1666 WHERE IS THE PLACE OF PET/CT IN DIAGNOSTIC IN PATIENTS WITH LYMPHOBLASTIC LYMPHOMA AND ACUTE LYMPHOBLASTIC LEUKEMIA WITH EXTRAMEDULLARY INVOLVEMENT?
Authors: O. Gavrilina, E. Parovichnikova, V. Troitskaya, G. Baskhaeva, K. Zarubina, I. Galtseva, V. Savchenko
Journal: HemaSphere (2019)

Background: Positron emission tomography/computed tomography (PET/CT) is emerging as an essential diagnostic tool in characterizing suspicious neoplastic lesions and staging malignant diseases. Most studies regarding the possible role of FDG‐PET/CT in the management of acute lymphoblastic leukemia (ALL) patients are very limited. But one can suggest the high role of PET/CT in the assessment of residual lesions after chemotherapy in patients with lymphoblastic lymphoma (LBL) and ALL with extramedullary involvements. Aims: The aim of the study was to estimate the ability to accumulate 18F‐FDG radiopharmaceuticals by tumor cells in PET/CT in patients with ALL/LBL and assess the prognostic value of the PET/CT after the consolidation therapy (with or without autologous stem cell transplantation (autoSCT)) in patients with Ph‐negative ALL/LBL who received therapy according to the protocols of the Russian research group ALL‐2009/ALL‐2016. Methods: PET/CT was performed in 3 patients with different types of newly diagnosed ALL before the start of the therapy and after the end of induction. Characteristic of patients were: the first‐ male, 55 age, with BII type Ph‐negative ALL, with t(6;11) with generalized bone involvement and ossalgia; the second ‐ female, 33 age, with BII type Ph‐positive ALL, p190type of transcript without extramedullary involvement; and the third‐ female, 28 age, with TIII type ALL, with TCR A/D rearrangement, with massive mediastinal lesion, bilateral renal and ovarium involvement. PET/CT was applied in 10 patients with Ph‐negative ALL/LBL after the end of consolidation by ALL‐2009/ALL‐2016 protocols. The characterization of patients (Table): 6/4 (60%/40%) M/F, 9/1 (90%/10%) B/T type Ph‐negative ALL, 8/1/1 (80%/10%/10%) with mediastinum/lymph nodes/renal and ovarium involvements, 3/7 (30%/70%) with or without bone marrow involvement, nobody with CNS involvement, 5/5 (50%/50%) with or without autoSCT, 3/7 (30%/70%) with or without radiotherapy in consolidation. Results: The results of PET/CT in three patients with different variants of newly diagnosed ALL/LBL were analyzed and it was shown that all patients had metabolic activity of 18F‐FDG in all morphologically and immunohistochemically (immunophenotypically) confirmed lesions (SUV 3,9‐8,7). An analysis of the results of PET/CT after the consolidation therapy with/without autoSCT in patients with Ph‐negative ALL was performed, and it has shown that all patients had PET‐negative remission of the disease and MRD negative status in bone marrow by flow cytometry. With a median follow‐up of 20.5 months (from 15 to 44 months), only one patient out of 10 patients had isolated CNS relapse after 10 months of remission. In another 9 patients, with a median CR duration of 19 months (from 14 to 43 months), complete clinical and hematological remission is maintained. Summary/Conclusion: The results demonstrated that all specific lesions in ALL/LBL patients, medullary and extramedullary, were capable to accumule 18F‐FDG in PET. This fact provides opportunities for further studies of this method in assessing the completeness of remission in patients with extramedullary lesions. The value of PET/CT in ALL/LBL patients with central nervous system involvement remained unexplored. If the suggestions arising from this report are confirmed, FDG‐PET/CT may be included in future clinical practice for disease staging, evaluating the response to the chemotherapy in identified lesions and in the restaging for recurrence of extramedullary disease. image