Hodgkin Variant of Richter's Transformation (HvRT) Among Chronic Lymphocytic Leukemia (CLL)/Small Lymphocytic Lymphoma (SLL) Patients in British Columbia (BC), Canada

Background: Richter transformation (RT) to diffuse large B-cell lymphoma (DLBCL) is a well-known complication of CLL/SLL, occurring in 2-10% of patients (pts); however, a minority transform to Hodgkin lymphoma, termed Hodgkin variant of RT (HvRT). Because of the rarity of HvRT, there is limited information regarding prognostic factors and treatment approach. The aim of this study was to evaluate clinical characteristics, treatment and survival of HvRT in a population based cohort of CLL/SLL pts in BC. Methods: Provincial databases were retrospectively reviewed from Jan. 1994 - Feb. 2020 to identify all CLL/SLL pts in BC with histologically proven HvRT using central pathology review. Overall survival (OS) was defined from HL diagnosis to death/last follow-up (f/u); progression-free survival (PFS) was defined from HL diagnosis to lymphoma progression, death or last f/u. Results: 32 pts with HvRT from CLL (N=18) or SLL (N=14) were identified. Median f/u for living pts from CLL/SLL diagnosis was 129 months (mos) (range, 25-504). Most pts were male (87%) with median age at CLL/SLL and HL diagnoses of 64 years (y) (range, 35-83) and 71 y (range, 51-86), respectively. Median interval from CLL/SLL diagnosis to HvRT was 67 mos (range, 0-403), with composite CLL/SLL and HL diagnosed in 5 pts (16%). At CLL/SLL diagnosis, 50% (15/30) had Rai or Ann Arbor stage 3-4; 7% (1/14) had del(17p), 29% (4/14) del(13q), 0% (0/14) del(11q), 29% (4/14) trisomy 12 and 50% (7/14) had no abnormalities. Most pts (80%; 24/30) had treatment for CLL/SLL prior to HvRT: purine analogues (PA) in 67% (20/30), alkylators in 50% (15/30), rituximab in 60% (18/30) and ibrutinib in 17% (5/30%). Median number of treatment lines prior to HvRT was 2 (range, 0-4) and median time from last CLL/SLL therapy to HvRT was 15 mos (range, 1-107). HvRT was characterized by Ann Arbor stage 3-4 in 87% (25/29) of cases, B symptoms in 67% (18/27), International Prognostic Score (IPS) ≥ 4 in 67% (18/27), and Epstein Barr virus (EBV) positivity in 59% (13/22). Richter Prognosis Score (RPS) was low risk (RPS 0-1) in 48% (10/21 pts), low-intermediate (RPS 2) in 33% (7/21) and high-int/high (RPS 3-5) in 19% (4/21). ABVD (adriamycin, bleomycin, vinblastine and dacarbazine) or ABVD-like therapy (AVD or modified ABVD dose/regimen) was the most common primary HL therapy, used in 65% (20/31). Others were alkylator-based regimens in 13% (4/31); brentuximab, ibrutinib and cyclosporine in 1 case each, and local excision in 1