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Single tumor cell uptake and dosimetry of technetium‐99m Fab′ anti‐CD22 in low‐grade B‐cell lymphoma
Author(s) -
Lindén Ola,
Hindorf Cecilia,
Tennvall Jan,
Segrén Sverker,
Wingardh Karin,
Strand SvenErik
Publication year - 2002
Publication title -
cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.052
H-Index - 304
eISSN - 1097-0142
pISSN - 0008-543X
DOI - 10.1002/cncr.10296
Subject(s) - cd22 , nuclear medicine , medicine , cd19 , raji cell , lymphoma , flow cytometry , b cell , b cell lymphoma , cell , antibody , pathology , chemistry , immunology , biochemistry
BACKGROUND A patient with follicular lymphoma was investigated with 0.5 mg Fab′ anti‐CD22 labeled with 1100 MBq technetium‐99m ( 99m Tc). A computed tomography scan performed a week later revealed regression. This unexpected response prompted an investigation of single cell dosimetry of low‐energy electron emitters. METHODS Another patient with low‐grade, unclassifiable B‐cell lymphoma with a low expression of CD22 was injected with 99m Tc anti‐CD22. Blood samples were drawn 30 minutes, 4 hours, and 24 hours after injection. Lymphoma cells (CD19+) and T cells (CD3+), which served as control cells, were separated using a flow cytometer. The radioactivity of the two cell populations was measured in an NaI(Tl) well‐type detector. The mean uptake per cell and absorbed dose were calculated. The CD22 expression of the patient's cells and of a B‐cell lymphoma cell line (Raji) were assessed by flow cytometry for the extrapolation of the absorbed dose from the patient's cells to a cell line with higher CD22 expression. RESULTS The average number of 99m Tc atoms per CD19+ and CD3+ cell 4 hours postinjection were 5.4 and 0.054, respectively. Depending on the assumed ratio between antibody and CD22 molecules (1:2 or 1:1), the CD22 expression on the patient's cells and Raji cells varied from 2800 to 5700 and from 37,000 to 74,000 per cell, respectively. The average absorbed dose per cell ranged from 4 × 10 −7 to 0.1 grays (Gy). CONCLUSIONS It seems feasible to assess the mean single tumor cell uptake of 99m Tc targeted by Fab′ anti‐CD22 in a patient's lymphoma using sorted cell populations, thereby allowing single cell dosimetry. Extrapolation of the absorbed dose from 99m Tc to cells with higher CD22 expression was made and under certain conditions absorbed doses of 0.1 Gy were obtained, indicating the potential relevance of low‐energy electron emitters to therapy. Cancer 2002;94:1270–4. © 2002 American Cancer Society. DOI 10.1002/cncr.10296