Purpose: We used small animal positron emission tomography (PET) imaging to monitor the time-course of tumor metabolic response to hormone and chemotherapy in a murine model of hormone-sensitive breast cancer.
Procedures: Estrogen receptor positive murine mammary carcinomas were inoculated in Balb/c mice. Small animal PET imaging using 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) was used to assess tumor metabolic activity. Imaging was done before and at days 1, 7, and 14 after the administration of doxorubicin, methotrexate, letrozole, or placebo. The tumor uptake of FDG was calculated from a region-of-interest drawn around the tumor.
Results: All treatments resulted in a decrease in tumor growth rate and end volume compared to untreated control. FDG uptake was also markedly decreased after treatment although a flare reaction was observed on PET at day 7, the intensity of which varied according to the treatment modality.
Conclusion: PET imaging is sensitive to detect early changes associated with therapy in murine breast cancer models. A flare reaction was observed 7 days after the initiation of therapy.