Radiotherapy With Rituximab Is Better than Radiotherapy alone In First Line Treatment Of Localized Follicular Lymphoma. Time To Change a Standard Strategy?

Localized stages of follicular lymphoma (I-II) have been traditionally treated with involved field radiotherapy (IF-RT), which seems to be able to cure a significant proportion of patients. On the other hand, nearly half of patients relapse within 10 years. The late distant relapses remain the problem. Rituximab (anti CD20 antibody) is low-toxic, efficient systemic therapy for follicular lymphoma (FL). In vitro models bring the evidence of significant synergism between rituximab and radiotherapy. Up to now, there are no clinical data about clinical benefit of rituximab addition to the IF-RT. This study compares IF-RT alone vs. IF-RT with rituximab in early-stages of FL.

Between 2005-2012, through the prospectively maintained multicentric database (Czech Lymphoma Group; CLG), we identified patients with stage I-II FL treated with IF-RT (dose ≥ 24Gy) or IF-RT (dose ≥ 24Gy) with rituximab or rituximab alone. Patients receiving IF-RT with chemotherapy were not included. Complete staging including CT (neck, thorax, abdomen and pelvis) and bone marrow biopsy was performed at diagnosis. We compared EFS and OS between these three treatment arms. Rituximab (4 doses á 375mg/m²) was administered prior start of radiotherapy in combined arm. The total doses of rituximab varied between 4-8 doses á 375mg/m² in rituximab monotherapy subgroup as well as in combined arm. Response to treatment was evaluated with CT 6-12 weeks after last dose of therapy.

For the study period, approximately 1700 pts. of FL were identified in CLG database; 101pts with stage I-II FL (grade 1-3A) were included in the analysis. 65 patient were treated with radiotherapy alone (RT), 14 pts. with rituximab alone (R) and 14 pts. received rituximab and radiotherapy (R+RT), 8 pts. were excluded because of incomplete data. Median follow up was 4.57 (2.25- 12.6) years since diagnosis. There were no differences of age, performance status, FLIPI, proportion of bulky or extranodal tumor. In subgroup treated with R+RT was higher proportion of FL grade 3A in comparison with R or RT alone arms (35% vs. 1.5% vs. 7.5%; p.007). Complete response rate was 92% in RT arm, 100% in arm with R+RT and 86% in group treated with R alone, difference did not reach statistical significance. Median of event free survival was 3.35years in RT group, not reached in R+RT arm and 5.1 years in patients treated with R alone. EFS differences are statistically significant (p.035), but with no impact on overall survival.

In spite of fact, that RT is considered to be a good initial treatment for localized FL, rituximab alone or better in combination with RT seems to give better results in terms of long-term global control of disease. Our preliminary results should be confirmed with other studies and longer follow up is needed to verify or not the impact of rituximab on survival in early stages of FL.

The work is support by research grant NT/12193-5 and MHCZ-DRO FNBr65269705.

Mayer:Roche: Consultancy, Research Funding; Glaxo: Consultancy, Research Funding. Trneny:Roche: Honoraria, Research Funding.