INTRODUCTION
Predominant lymphocytic nodular Hodgkin's lymphoma (PLNHL) is a rare lymphoma. No evidence-based guidelines for initial or relapse treatment have been published.
Two patients relapsing 12 and 17 months after initial treatment with rituximab were included in a phase II trial of radioimmunotherapy (RIT).  Yttrium 90 was coupled to rituximab (90Y-rituximab) ; a first infusion of rituximab is given (250mg/m2) d1 and 8  and directly followed by 90Y-rituximab (14,8 MBq/kg). The rational of using unlabeled (“cold”) antibodies before RIT is to provide a more favorable biodistribution profile. 

CASE # 1:
A 27 y.o. man noticed in April 2008 a bulky right axillary mass (CS IA). 
The diagnosis of NLPHL, CD20+ was established. The treatment consisted in radiation therapy (RT) and 4 consolidation courses of Rituximab. The 18FDG-PET/CT after 6 months showed a complete metabolic response but after 18 months a moderate hypermetabolic activity in infracarinal lymphadenopathies and spleen is described. In October 2010, relapse is confirmed by lymph node and a RIT is accepted by the patient. This leads to a complete remission which is still ongoing after 8 years. No adverse events were observed.

CASE #2:
A 38 y.o. man presented with bilateral supraclavicular lymphadenopathies due to a  PLNHL (CD30 +, CD20 +) stage IIA. Rituximab treatment (4 weekly courses) was started in August 2007. Response assessment by18FDG-PET/CT, performed 4 months after the end of the treatment, showed a complete metabolic response. Eleven months after the end of treatment, 18FDG-PET/CT revealed a 2cm diameter retroperitoneal lymph node which increased to 5 cm in diameter at 21 months. RIT is started in September 2009, according to our protocol. Six months after RIT, 18FDG-PET/CT showed a complete metabolic remission, persisting 9 years later. No side effects are reported.

CONCLUSION 
PLNHL is a very sensitive disease as demonstrated by high cure rate in early stages. In two patients, salvage treatment with RIT, achieved complete response for 8+ years compared to less than 2 years after rituximab alone. To our knowledge, RIT has never been reported for this indication.

Long-term follow-up of 2 patients treated with 90Y-rituximab Radioimmunotherapy for relapse of Predominantly Lymphocytic Nodular Hodgkin's Lymphoma