Choline PET for Monitoring Early Tumor Response to Photodynamic Therapy

• Type of Material: Article
• Authors: Baowei Fei, Emory University; Hesheng Wang, Case Western Reserve University; Chunying Wu, Case Western Reserve University; Song-mao Chiu, Case Western Reserve University
• Language: English
• Date: 2010-01
• Publisher: Society of Nuclear Medicine
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2010 by the Society of Nuclear Medicine, Inc.
• Final Published Version (URL): http://jnm.snmjournals.org/content/51/1/130.long
• Title of Journal or Parent Work: Journal of Nuclear Medicine and Radiation Therapy
• ISSN: 0161-5505
• Volume: 51
• Issue: 1
• Start Page: 130
• End Page: 138
• Grant/Funding Information: National Cancer Institute : NCI
• Keywords: photodynamic therapy (PDT); choline molecular imaging; prostate cancer; tumor response; small-animal PET
• Research Categories: Health Sciences, Oncology

Abstract

Photodynamic therapy (PDT) is a relatively new therapy that has shown promise for treating various cancers in both preclinical and clinical studies. The present study evaluated the potential use of PET with radiolabeled choline to monitor early tumor response to PDT in animal models.Methods Two human prostate cancer models (PC-3 and CWR22) were studied in athymic nude mice. A second-generation photosensitizer, phthalocyanine 4 (Pc 4), was delivered to each animal by a tail vein injection 48 h before laser illumination. Small-animal PET images with 11C-choline were acquired before PDT and at 1, 24, and 48 h after PDT. Time–activity curves of 11C-choline uptake were analyzed before and after PDT. The percentage of the injected dose per gram of tissue was quantified for both treated and control tumors at each time point. In addition, Pc 4-PDT was performed in cell cultures. Cell viability and 11C-choline uptake in PDT-treated and control cells were measured. Results For treated tumors, normalized 11C-choline uptake decreased significantly 24 and 48 h after PDT, compared with the same tumors before PDT (P < 0.001). For the control tumors, normalized 11C-choline uptake increased significantly. For mice with CWR22 tumors, the prostate-specific antigen level decreased 24 and 48 h after PDT. Pc 4-PDT in cell culture showed that the treated tumor cells, compared with the control cells, had less than 50% 11C-choline activity at 5, 30, and 45 min after PDT, whereas the cell viability test showed that the treated cells were viable longer than 7 h after PDT. Conclusion PET with 11C-choline is sensitive for detecting early changes associated with Pc 4-PDT in mouse models of human prostate cancer. Choline PET has the potential to determine whether a PDT-treated tumor responds to treatment within 48 h after therapy.