Interventional therapy for human breast cancer in nude mice with (131)I gelatin microspheres ((131)I-GMSs) following intratumoral injection

INTRODUCTION: The aim of this study was to investigate the effects of (131)I gelatin microspheres ((131)I-GMS) on human breast cancer cells (MCF-7) in nude mice and the biodistribution of (131)I-GMSs following intratumoral injections. METHODS: A total of 20 tumor-bearing mice were divided into a treatment group and control group and received intratumoral injections of 2.5 mci (131)I-GMSs and nonradioactive GMSs, respectively. Tumor size was measured once per week. Another 16 mice received intratumoral injections of 0.4 mci (131)I-GMSs and were subjected to single photon emission computed tomography (SPECT) scans and tissue radioactivity concentration measurements on day 1, 4, 8 and 16 postinjection. The 20 tumor-bearing mice received intratumoral injections of 0.4 mci [(131)I] sodium iodide solution and were subjected to SPECT scans and intratumoral radioactivity measurements at 1, 6, 24, 48 and 72 h postinjection. The tumors were collected for histological examination. RESULTS: The average tumor volume in the (131)I-GMSs group on post-treatment day 21 decreased to 86.82 ± 63.6%, while it increased to 893.37 ± 158.12% in the control group (P < 0.01 vs. the (131)I-GMSs group). (131)I-GMSs provided much higher intratumoral retention of radioactivity, resulting in 19.93 ± 5.24% of the injected radioactivity after 16 days, whereas the control group retained only 1.83 ± 0.46% of the injected radioactivity within the tumors at 1 h postinjection. CONCLUSIONS: (131)I-GMSs suppressed the growth of MCF-7 in nude mice and provided sustained intratumoral radioactivity retention. The results suggest the potential of (131)I-GMSs for clinical applications in radiotherapy for breast cancer.