Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin (TM) radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma
Ga. Wiseman et al., Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin (TM) radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma, CR R ONC H, 39(1-2), 2001, pp. 181-194
Radiation dosimetry studies were performed in patients with non-Hodgkin's l
ymphoma (NHL) treated with Y-90 Zevalin (TM) ((90)yttrium ibritumomab tiuxe
tan, IDEC-Y2B8) on a Phase III open-label prospectively randomized multicen
ter trial. The trial was designed to evaluate the efficacy and safety of Y-
90 Zevalin radioimmunotherapy compared to rituximab (Rituxan (R), MabThera
(R)) immunotherapy for patients with relapsed or refractory low-grade, foll
icular, or transformed NHL. An important secondary objective was to determi
ne if radiation dosimetry prior to Y-90 Zevalin administration is required
for safe treatment in this patient population. Methods: Patients randomized
into the Zevalin arm were given a tracer dose of 5 mCi (185 MBq) In-111 Ze
valin ((111)indium ibritumomab tiuxetan) on Day 0, evaluated with dosimetry
, and then administered a therapeutic dose of 0.4 mCi/kg (15 MBq/kg) Y-90 Z
evalin on Day 7. Both Zevalin doses were preceded by an infusion of 250 mg/
m(2) rituximab to clear peripheral B-cells and improve Zevalin biodistribut
ion. Following administration of In-111 Zevalin, serial anterior and poster
ior whole-body scans. were acquired and blood samples were obtained. Reside
nce times for 90Y were estimated for major organs, and the MIRDOSE3 compute
r software program was used to calculate organ-specific and total body radi
ation absorbed dose. Patients randomized into the rituximab arm received a
standard course of rituximab immunotherapy (375 mg/m(2) weekly x 4). Result
s: In a prospectively defined 90 patient interim analysis, the overall resp
onse rate was 80% for Zevalin vs. 44% for rituximab. Wr all patients with Z
evalin dosimetry data (N = 72), radiation absorbed doses were estimated to
be below the protocol-defined upper limits of 300 cGy to red marrow and 200
0 cGy to normal organs. The median estimated radiation absorbed doses were
71 cGy to red marrow (range: 18-221 cGy), 216 cGy to lungs (94-457 cGy), 53
2 cGy to liver (range: 234-1586 cGy), 848 cGy to spleen (range: 76-1902 cGy
), 15 cGy to kidneys (0.27-76 cGy) and 1484 cGy to tumor (range: 61-24 274
cGy). Toxicity was primarily hematologic, transient, and reversible. The se
verity of hematologic nadir did not correlate with estimates of effective h
alf-life (half-life) or residence time of Y-90 in blood, or radiation absor
bed dose to the red marrow or total body. Conclusions Y-90 Zevalin administ
ered to NHL patients at non-myeloablative maximum tolerated doses delivers
acceptable radiation absorbed doses to uninvolved organs. Lack of, correlat
ion between dosimetric or pharmacokinetic parameters and the severity of he
matologic nadir suggest that hematologic toxicity is more dependent on bone
marrow reserve in this heavily pre-treated population. Based on these find
ings, it is safe to administer Y-90 Zevalin in this defined patient populat
ion without pre-treatment In-111-based radiation dosimetry. (C) 2001 Elsevi
er Science Ireland Ltd. All rights reserved.