Iododeoxyuridine uptake and retention as a measure of tumor growth.
Iodine-131-iododeoxyuridine (IUdR) uptake and retention was measured in two C6 glioma cell lines (C6m and C6a) with different growth characteristics. Animals with intracerebral (i.c.) C6a tumors had a mean survival of 16 days, whereas only 1 of 20 animals with i.c. C6m tumors died during an 8-wk period of observation. The growth of i.c. C6m tumors could be described by the Gompertz equation; tumor doubling time increased from 1.9 to 5.2 days between Days 8 and 16 after tumor inoculation. Corresponding measurements of 131I-IUdR uptake and retention (24 hr after IUdR administration) by i.c. C6m tumors were also time-dependent and decreased from 0.075 to 0.027 to 0.011 %dose/g in 8-, 10- and 16-day-old tumors, respectively. Iodine-131-IUdR uptake in "rapidly growing" i.c. C6a tumors was substantially higher (0.30 %dose/g at 24 hr) than that in "slowly growing" i.c. C6m tumors and corresponded with differences in the survival data. Subcutaneous C6a tumors had comparable high uptake values (0.49 %dose/g at 24 hr), and 93% of total tumor radioactivity was recovered in DNA 24 hr after IUdR administration. Clearance of radioactivity was rapid in nonproliferative tissues; more than 80% of plasma radioactivity was cleared in 24 hr. Tumor-to-cortex radioactivity ratios ranged from 100/1 to 120/1 and 150/1 between 24, 48 and 96 hr after IUdR injection respectively. A "washout strategy," which reduces tissue background activity and increases specificity for PET and SPECT imaging of IUdR-DNA incorporation, is possible with longer-lived radioisotopes of iodine.
Tjuvajev
J
J
Cotzias Neuro-Oncology Laboratory, Memorial Sloan Kettering Cancer Center, New York, NY 10021.
Muraki
A
A
Ginos
J
J
Berk
J
J
Koutcher
J
J
Ballon
D
D
Beattie
B
B
Finn
R
R
Dahighian
F
F
Blasberg
R
R
D000818:Animals; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000401:mortality; D005910:Glioma / Q000000981:diagnostic imaging* / Q000401:mortality; D007065:Idoxuridine; D007457:Iodine Radioisotopes; D008297:Male; D051381:Rats; D011920:Rats, Inbred WF; D017208:Rats, Wistar; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D014407:Tumor Cells, Cultured
D007457:Iodine Radioisotopes; D007065:Idoxuridine