ESTRO 2024 - Abstract Book

S1153

Clinical - Haematology

ESTRO 2024

Oncologico Veneto - IRCCS, Radiotherapy Unit, Padova, Italy. 5 Fondazione IRCCS Istituto Nazionale Tumori, Radiation Oncology Unit, Milano, Italy. 6 Centro di Riferimento Oncologico di Aviano CRO-IRCCS, Department of Radiation Oncology, Aviano, Italy. 7 Azienda Ospedaliero-Universitaria Policlinico Umberto I, Sapienza, University of Roma, Department of Radiotherapy, Roma, Italy. 8 Radiotherapy Oncology, Sant'Andrea Hospital, Department of Medicine and Surgery and Translational Medicine, Roma, Italy. 9 A. Businco Hospital, ARNAS G. Brotzu, Department of Radiation Oncology, Cagliari, Italy. 10 Azienda Unità Sanitaria Locale, Piacenza, Radiation Oncology Center, Piacenza, Italy. 11 Santa Maria della Misericordia Hospital, Radiation Oncology Unit, Rovigo, Italy. 12 S. Maria Hospital, Radiation Oncology Center, Terni, Italy. 13 Santa Croce e Carle Hospital, Radiation Oncology, Cuneo, Italy

Purpose/Objective:

Early-stage extra-nodal indolent lymphoma presents in a variety of organs and with different histologies. It is typically diagnosed in a localized stage, making local treatments the preferred therapeutic approach. However, the treatment regimens used are variable, with some patients receiving systemic therapy despite the localized nature of disease. Literature data showed that radiotherapy (RT) was associated with optimal survival outcomes in this disease setting. Still, currently available studies have enrolled small patient samples and lacked homogeneity among patient cohorts. Studies have yet to provide conclusive evidence regarding the best therapeutic approach and, with regards to RT, the best dose regimen to adopt based on disease location.

Material/Methods:

We retrospectively included patients with stage IE or IIE indolent lymphoma referred to 13 Italian centers between 2003 and 2018. This study enrolled patients with any indolent histology (marginal zone lymphoma – MZL; follicular lymphoma – FL; small lymphocytic lymphoma – SLL; lymphoplasmacytic lymphoma – LPL; and Waldenström macroglobulinemia – WM) and any disease location except skin, testicle and central nervous system. All eligible patients had received RT with curative intent; inclusion criteria allowed the association of systemic therapy, with either rituximab or chlorambucil. Local disease control (LC), systemic disease control (SC), local relapse or systemic progression (RP), progression-free survival (PFS) and overall survival (OS) were analyzed through the univariate and multivariate (MVA) Cox proportional hazards regression and Kaplan-Meier method since the last day of RT.

Results:

Our study included 259 patients with early-stage extra-nodal lymphoma, 224 of whom (87%) had stage I disease. 143 (55%) patients were female and the median age was 66 years (range 19-92). The most represented histologies were MZL (190 patients, 73%) and FL (57 patients, 22%). The most common disease locations were the orbits (82 patients, 32%), the stomach (50 patients, 19%), the salivary glands (39 patients, 15%) and the head and neck region (30 patients, 12%). Less frequent sites included: muscles and soft tissues, breasts, bone, duodenum, thyroid, lungs and liver. Less than half the patients underwent disease staging with PET-CT scan (115 patients, 44%), whereas bone marrow biopsy had been performed in 143 patients (55%). A minimal percentage of patients (2%) had bulky disease at diagnosis. All patients were treated with RT, which was associated with systemic therapy in only 43 patients (17%). Median follow-up after treatment was 56 months. At 5 years post-treatment, LC, SC and RP were, respectively, 94%, 81% and 77%. LC was not significantly affected by any prognostic factor, including lymphoma histology and radiation dose. At MVA, age and radiation dose were found to be associated with PFS. In particular, patients aged 70 or older had a worse PFS than their younger counterparts (HR 1.59, p=0.046); moreover, those who had received radiation doses of ³24 Gy had a better PFS than those who had undergone low-dose RT (LDRT) with 4 Gy (HR 0.47,