(P-277) An Updated Structured Review of the Epidemiology, Guidelines, and Real-world Treatment Patterns for Relapsed/refractory Primary Mediastinal Large B-cell Lymphoma

Background: Primary mediastinal large B-cell lymphoma (PMBCL) is a rare subtype of non-Hodgkin lymphoma that predominantly occurs in young adults. Treatment approaches are evolving, but the management of patients with PMBCL that are refractory to treatment remains a key challenge.

Objectives: A structured review was originally conducted from 1997‒2017 to understand the disease burden in PMBCL and refractory/relapsed (R/R) PMBCL. We provide an updated review (from 2017‒2020) on treatment patterns in R/R PMBCL, with a focus on understanding treatment advances in this area.

Methods: 3167 (1997‒2017) and 2091 (2017‒2020) records were screened, and 31 relevant studies were identified. Embase®, PubMed®, and the Cochrane library were searched for R/R PMBCL records from 1997‒2020, in accordance with PRISMA guidelines.

Results: The proportion of patients with R/R PMBCL was between 9.4‒13.5% (n=3 studies). There were 7 treatment guidelines for R/R PMBCL, including 4 published from 2017‒2020 (2 US, 1 Canada, and 1 UK). The guidelines recommended high-dose chemotherapy (HDT) and stem cell rescue (SCR) with/without radiotherapy in patients with R/R PMBCL. For patients that do not respond or continued to progress, the updated US and Canadian guidelines now recommend treatment with pembrolizumab (the only FDA-approved PD-1 inhibitor) and anti-CD19 chimeric antigen receptor-T (CAR-T) cell therapy for R/R PMBCL patients with ≥2 lines of prior systemic therapy. Real-world data were recorded in 28 studies (including 12 from 2017‒2020). Treatment patterns for R/R PMBCL were largely aligned with the guidelines and reported HDT, radiotherapy, SCR, PD-1 inhibitors, and anti-CD19 CAR-T cell therapy as the key options in these patients from cohorts in the United States, Canada, and Europe. Furthermore, there was evidence of a switch from autologous SCR to allogenic SCR for R/R PMBCL in the most recent studies.

Conclusions: This structured review provides an extensive overview of the evolving landscape in the management of patients with R/R PMBCL. It shows that treatment patterns quickly change to address unmet medical needs with new and approved therapies, such as pembrolizumab, being introduced into updated guidelines.