Real-world data on treatment and outcomes of patients with primary mediastinal large B-cell lymphoma: a Swedish lymphoma register study
Authors: Tove Wästerlid, Sverker Hasselblom, Joel Joelsson, Caroline E. Weibull, Georgios Rassidakis, Birgitta Sander, Karin E. Smedby
Journal: Blood Cancer Journal (2021)

Dear Editor,Primary mediastinal large B-cell lymphoma (PMBL) is an aggressive lymphoma subtype that predominantly affects women in their 3rd-4th decade.Due to the rarity of PMBL, optimal treatment, including choice of chemotherapy regimen and necessity of radiotherapy (RT), is not established [1][2][3] .In view of the low median age at diagnosis, minimising long-term toxicity while still achieving cure, is essential in ideal PMBL management.To improve knowledge regarding long-term outcomes and optimal management of PMBL we examined patient characteristics, treatment choice, relative survival and excess mortality among all patients registered with PMBL in the population-based Swedish Lymphoma Register (SLR) 2007-2018.Established in 2000, the SLR prospectively records lymphomaspecific patient characteristics and since 2007 also data on active treatment, treatment type and response, with a coverage of ∼95% of all lymphoma cases diagnosed in Sweden.Further, for cases included from the Stockholm area (n = 39) central pathology review (by experienced hematopathologists BS and GR) was performed on all patients with available material (n = 37) of which all were confirmed to be true PMBL cases.The study was approved by the Regional Board of the Ethical Committee in Stockholm (2015/2028-31/2).During the study period, 172 patients were registered with a PMBL diagnosis in the SLR, of whom 98 (57%) were women.The median age was 37.5 years (range 18-85).Median follow-up time for patients alive at end of follow-up was 8 years (range 1.7-13.6years) and 24 (14%) of the patients died.The majority of patients presented with stage I-II disease (n = 116, 67%), 154 (90%) had elevated serum-lactate dehydrogenase (S-LDH), and 152 (88%) had a WHO performance status (PS) score of 0-1.Most patients had bulky disease (>10 cm in diameter) at diagnosis (n = 119, 69%) and 44 (26%) had extranodal disease (Table 1).For 92% of the patients, PET was used to assess response.Increasing age was associated with poorer survival (HR continuous age = 1.07, 95% CI: 1.05-1.09).Other factors associated with higher mortality rates in unadjusted and age-adjusted Cox models were PS 2-4 (HR = 3.6, 95% CI: 1.4-9.1)and age-adjusted (aa) IPI 2-3 (HR = 3.0, 95% CI: 1.3-6.9).Treatment information was available for 156 (91%) patients, whom all received immunochemotherapy, apart from one patient who did not receive active treatment.The most commonly administered regimen was R-CHOEP-14 (n = 90, 58%).Sixteen patients (10%) received R-Hyper-CVAD (cyclophosphamide, doxorubicin, vincristine, dexamethasone, high dose methotrexate and cytarabine), 37 (24%) R-CHOP-14 (of which 3 were R-CHOP-21), 11 (7%) DA-EPOCH-R and 1 (<1%) R-VACOP-B.The median age was highest among patients treated with R-CHOP (49 years), compared to 35, 38 and 41 years for patients administered R-CHOEP-14, R-Hyper-CVAD or DA-EPOCH-R, respectively.Apart from age, patient characteristics were similar between regimens, but with a slightly higher proportion of patients with PS 2-4 in the R-CHOP group and patients with stage III-IV disease in the R-Hyper-CVAD group.The majority (95%) of patients completed the planned number of