P1180: ARE EXTRANODAL LIMITED-STAGE DIFFUSE LARGE B-CELL LYMPHOMA MORE AGRESSIVE THAN NODAL FORMS?

Abstract

Background: Limited-stage diffuse large B-cell lymphoma (DLBCL) is associated with favourable outcomes with overall survival of 70-80% at 10 years. Stage-modified IPI (sm-IPI) predicts the risk of relapse and death based on clinical factors that do not include extranodal (EN) involvement, although in some studies it has been associated with worse outcomes. Aims: To analyse the characteristics and outcomes of limited-stage DLBCL in a single center series and evaluate the prognostic impact of EN involvement. Methods: We conducted a retrospective analysis of consecutive patients with newly diagnosed stage I-II DLBCL treated with curative intent at a single centre from 2015 to 2019. Primary central nervous system (CNS) lymphoma, primary testicular lymphoma, primary mediastinal B-cell lymphoma and transformed lymphoma were excluded. Response to therapy was assessed according to Lugano criteria. Overall (OS) and progression free survival (PFS) were calculated by Kaplan-Meier method and comparisons done by the log rank test. Cumulative incidence of relapse was calculated using competing risk models and Gray test for group comparisons. Cox regression was used to identify prognostic factors for PFS. Results: Of 152 patients identified, 53 (35%) had EN disease and 99 (65%) were nodal (N). The most common EN sites were stomach (30%), sinus/nasal cavity (13%), skin and soft tissue (9%) and breast (9%). Seventy-two (47%) had low risk sm-IPI (45 N; 27 EN). Clinical characteristics were similar between both groups, except for stage (stage I in 50.9% of EN vs 32.3% of N cases) and bulky disease (EN 15.1% vs N 37.4%). All patients received R-CHOP (median 6 cycles; range 1-8). Eight patients, all with EN involvement (3 sinus/nasal cavity, 2 breast, 2 bone and 1 orbit), received CNS prophylaxis. Seventeen out of 152 patients received additional radiotherapy (RT), 71% of whom had nodal involvement; 16/17 were irradiated due to bulky disease and/or treatment with abbreviated immunochemotherapy. Globally, 89% patients had a complete response (CR) to treatment: 85% in the N and 96% in the EN group (p=0.212). Nine patients relapsed at a median of 18 (7-52) months after obtaining CR (6 from the N and 3 from the EN group). The 4-year cumulative incidence of relapse was similar: 11.2% (95%CI 9.0-13.9%) in EN and 6.7% (95%CI 5.9-7.5%) in N group (p=0.778). No gastric lymphomas relapsed. The most common sites of relapse were lymph nodes (3), soft tissue (3) and CNS (2). Nineteen (14 N; 5 EN) patients died at a median of 12 (0-47) months after starting treatment, mostly (52.6%) due to lymphoma progression. With a median follow-up of 43 months, 4-year OS and PFS were 87% and 82%, respectively. No significant survival differences were observed in patients with N or EN presentation with a 4-year PFS of 81.8% and 81.3% (p=0.428), respectively. On multivariable analysis adjusting for RT, sm-IPI and bulky disease, EN involvement was not associated with a decreased PFS compared with N involvement (HR 0.77; 95%CI 0.31-1.90; p=0.570). Image:Summary/Conclusion: Our study corroborates the very favourable outcomes of localized DLBCL. We could not find differences in PFS according to N and EN presentations when controlling for other prognostic factors. These results do not support different treatment strategies for EN disease; however, due to limited sample size the role of RT and the prognostic impact of specific locations cannot be fully ascertained.