Abstract: S1597

Type: Oral Presentation

Presentation during EHA24: On Sunday, June 16, 2019 from 08:00 - 08:15

Location: Hall 5

Background

The role of consolidation radiotherapy (RT) after rituximab-chemotherapy (R-CT) in DLBCL is not completely defined. Historically, bulky sites at diagnosis are irradiated after R-CT, whereas residual disease  at other sites is considered as treatment failure. Since  2007, complete remission (CR)  is defined as PET negativity  and some groups postulated that PET negative areas after R-CT do not need  consolidation RT.

Aims
To assess  the role of RT in PET-negative and in PET-positive  low-risk DLBCL patients after R-CT

Methods
The DLCL10 trial  was a phase II study of  patients >=18 years with DLBCL defined at low risk according to the MiNT study,(aa IPI 0 and bulky, aa IPI 1 with/without bulky) conducted in 19  FIL centers. Patients  were treated with 6 courses  of RCHOP-14 or R-CHOP-21 and final response was evaluated with FDG-PET. Both pre and post treatment PET scans were centrally reviewed through the Widen web platform by a panel of five nuclear medicine experts. Positive scans were those centrally classified with Deauville score 3-4-5 .The first 2 concordant reviewers decided the final results. Patients with one residual FDG-uptaking area (RUA) were planned to receive  RT, 36 Gray involved-field, regardless of  the presence of bulky disease at diagnosis, while patients with multiple RUA were shifted to salvage systemic therapy. Primary aim was to obtain  2-year PFS of at least 85% for PET negative patients observed after R-CT; secondary endpoints were overall survival and response

Results
From January 2012 to December 2017, 115 consecutive patients were enrolled, and 109 were evaluable. Patients had a median age of 58 yrs (47-65); M:F 60/49; 90% DLBCL de novo. Fifteen patients  presented with aa IPI 0, and 94 with aa IPI 1, among whom 20  with bulky disease; 72 patients received  RCHOP-14 and 37 RCHOP-21. The median follow-up was 36 months and 6 patients died (2 lymphoma, 3 toxicitiy, 1 unknown). A total of 105 patients completed the chemotherapy program, while four were discontinued for lymphoma progression (1), toxicity (2, both died) and unknown cause (1). At the end of treatment 83 patients  had negative PET, whereas 17 had single RUA  and received RT. In PET-negative patients, PFS was 90.6% (95% CI 81.1-95.4) at 2 years and 88.7% (95% CI 78.4-94.3) at 3 years.  After RT, 15 out of 16 evaluable cases reached CR, one PR and one was not evaluable. None of them relapsed. Thus, all patients with positive focal findings after R-CT were cured with focal RT.  Concerning the 35 patients with bulky disease, 20  reached negative PET and 15 had RUA after R-CT (1 PD). There were two relapses in the negative PET/non irradiated group and none in the  positive PET /RT group.  In the total population, 3-year PFS and OS are 85.1% (95%CI 76.4-89.3) and 94% (95% CI 87.3-97.7), respectively.

Conclusion
Our data suggest that irradiating only sites of unique residual PET uptake, regardless of bulky at onset, can be considered as  a reasonable strategy for low risk DLBCL patients. In patients with bulky disease, PET-driven RT allowed RT sparing in approximately half of patients. Moreover, consolidation RT in those with  focal residual PET positivity, guaranteed excellent prognosis (17/17 cured) and has to be recommended as a valid option.

Session topic: 19. Aggressive Non-Hodgkin lymphoma - Clinical

Keyword(s): Diffuse large B cell lymphoma, International prognostic index, PET, Radiotherapy