The influence of tumor stage and metastasis on the biodistribution of gallium-67 citrate in the murine Lewis lung carcinoma model

The biodistribution of i.v. administered [67Ga]citrate was investigated in the Lewis lung carcinoma/male B6D2F1 mouse model. Tumors were implanted intramuscularly (10(5) cells or 10(6) cells in suspension) into the thigh, or subcutaneously (10(7) cells or 2 mm3 fragments) into the tail of recipient mice. Intramuscular tumors were allowed to grow for 16, 24, or 33 days; tail tumors developed for 2 wk (fragment implants) or 3 wk (10(7) cells in suspension) after which the primary tumor was amputated along with adjacent fragments of the tail tissue. Gamma camera scintigraphy and dissection/radiometric biodistribution studies indicated that: (a) tumors and metastases took up 5-6% of the injected dose/g except when large necrotic areas were present in the primary tumor; (b) blood levels of 67Ga increased in all tumor-bearing animals, with up to tenfold increases in the i.m. tumor model at later stages of the growth; (c) hepatic uptake increased as a function of tumor size/age, and (d) all tissue:blood ratios declined as the neoplastic tissues progressed. The results are discussed with respect to tumor progression and metastatic disease.