Bioevaluation study of 32P-CP-PLLA particle brachytherapy in a rabbit VX2 lung tumor model

Objective: The purpose of this study was to investigate the therapy effects of intratumoral administration of P-32-CP-PLLA particles in a rabbit VX2 lung tumor model. Methods: 16 rabbits with tumors were randomly divided into 4 groups. 4 rabbits served as untreated controls, and others received intratumoral administration of P-32-CP-PLLA particles with CT guidance. The total radioactivities in treated groups were as follows: a low activity was 93 MBq (n=4) (group 1), a medium activity was 185 MBq (n=4) (group 2) and a high activity was 370 MBq (n=4) (group 3). Brachytherapy treated VX2 tumors underwent F-18-FDG PET/CT at 0 day, 3 day, 7 day and 14 day postinjection. In control group, F-18-FDG PET/CT images were acquired at the same time points but without any treatment. Bremsstrahlung SPECT images were performed at 14 days after intratumoral brachytherapy in treated groups. After Bremsstrahlung SPECT and last F-18-FDG PET/CT imagings, the rabbits were euthanized and the tumors were removed for histological examination. Results: Bremsstrahlung SPECT images study indicated that there was no leakage of P-32 out of the injection site at 14 days after treatment. Compared with the control, the tumor volumes in treated groups significantly decreased, and P-32-CP-PLLA particle produced a reduction in maximum or mean SUV of VX2 tumor (p < 0.05). The percentage changes in maximum and mean SUV gradually decreased in group 1 and group 2 from day 3 to day 14 (p < 0.05). A transient increase in F-18-FDG accumulation at group 3 occurred due to the inflammatory reaction elements. Activity dependence was seen in HE and PCNA staining after 14 days treatment among three treated groups (p < 0.05). Conclusions: Our data suggested that P-32-CP-PLLA particle localized on the injecting sites. This novel brachytherapy device efficiently suppressed the growth of the VX2 tumors implanted in the rabbit. (C) 2012 Elsevier Ltd. All rights reserved.