The Prognostic Value of Positron Emission Tomography Findings in the Treatment of Primary Mediastinal (Thymic) Large B-Cell Lymphoma

BACKGROUND. Combined positron emission tomography/computed tomography (PET-CT) with [18F]fluorodeoxyglucose is an essential instrument of monitoring the response to chemotherapy in primary mediastinal (thymic) large B-cell lymphoma (PMBCL). Of outstanding interest is the interpretation of PET-CT findings with respect to the frequent persistence of large residual mediastinal tumor after the end of drug therapy in PMBCL patients.

AIM. To assess the prognostic value of PET-CT findings at different treatment stages in patients with newly diagnosed PMBCL.

MATERIALS & METHODS. This study is based on the clinical data from 28 PMBCL patients (altogether, 131 patients are followed-up) who were treated with R-DA-EPOCH ± radiotherapy at the NN Blokhin National Medical Cancer Research Center from 2011 to 2024. The median age was 35 years (range 21–48 years), most patients were women (n = 23; 82 %). This group of patients was selected because of the availability of PET-CT data to be closely analyzed prior to treatment, after 3 cycles (interim PET-CT), and by the end of the drug stage. This paper focuses on the data of 20 PMBCL patients including not only Deauville criteria (DC) for response but also the following technically determinable volumetric parameters: total metabolic tumor volume (TMTV), total lesion glycolysis (TLG), as well as standardized uptake values (SUVmax, SUVpeak, ΔSUVmax, ΔSUVpeak, and rSUVmax), maximum diameter (Dmax and ΔDmax), and products of perpendicular lesion diameters (PD, ΔPD).

RESULTS. With a 23-month median follow-up, the 2-year progression-free survival (PFS) in the total group was 78.6 % whereas the 2-year overall survival was 100 %. Incomplete metabolic response (DC 4–5) was reported in 19 (68 %) patients by the interim PET-CT and in 15 (54 %) patients by the end-of-treatment PET-CT. At the same time, the prognosis in patients with DC 4 and DC 5 was markedly different, but the 2-year PFS in the groups with complete (DC 1–3) and partial (DC 4) metabolic response appeared to be identical and accounted for 85 %. Moreover, all patients with DC 5 showed disease progression after chemotherapy. In PMBCL, two volumetric parameters (TMTV and TLG) have a particularly high prognostic value: the 2-year PFS in the group with high and low TMTV was 40 % and 93 %, respectively, and with high and low TLG it was 57 % and 92 %, respectively.

CONCLUSION. PET-negative status (DC 1–3) confirmed already by the interim analysis is a reliable factor for favorable prognosis in PMBCL. After completing drug therapy, a considerable proportion of patients show incomplete metabolic response (DC 4–5). However, long-term survival rates corresponding to DC 4 are noninferior to those in patients with DC 1–3, whereas in patients with DC 5, they are considerably worse. High TMTV and TLG values prior to chemotherapy are associated with unfavorable course of the disease.

• A.S. Subbotin NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-4648-2362 (unauthenticated)
• Arman Vachakanovich Arakelyan NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522; IM Sechenov First Moscow State Medical University, 2 korp. 4 Bolshaya Pirogovskaya ul., Moscow, Russian Federation, 119435 https://orcid.org/0000-0003-4911-0959 (unauthenticated)
• G.S. Tumyan NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-5771-4413 (unauthenticated)
• V.V. Solomyanyi NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0009-0007-6294-5826 (unauthenticated)
• B.M. Khakulova NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0001-7344-7688 (unauthenticated)
• A.A. Semenova NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0003-4951-3053 (unauthenticated)
• M.Yu. Kichigina NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-2715-2528 (unauthenticated)
• I.Z. Zavodnova NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0001-6674-8634 (unauthenticated)
• V.O. Shpirko NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-2300-0332 (unauthenticated)
• Yu.I. Klyuchagina NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522; IM Sechenov First Moscow State Medical University, 2 korp. 4 Bolshaya Pirogovskaya ul., Moscow, Russian Federation, 119435 https://orcid.org/0000-0003-2748-9208 (unauthenticated)
• S.F. Ramazanova NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0009-0008-7084-0060 (unauthenticated)
• U.G. Koshkina NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0009-0000-1023-5426 (unauthenticated)
• O.P. Trofimova NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-7204-370X (unauthenticated)
• M.A. Senchenko NN Blokhin National Medical Cancer Research Center, 23 Kashirskoye sh., Moscow, Russian Federation, 115522 https://orcid.org/0000-0002-9921-5620 (unauthenticated)
• V.Yu. Kirsanov IM Sechenov First Moscow State Medical University, 2 korp. 4 Bolshaya Pirogovskaya ul., Moscow, Russian Federation, 119435 https://orcid.org/0000-0003-1034-4432 (unauthenticated)

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