The Effects of Pulsed Radiation Therapy on Tumor Oxygenation in 2 Murine Models of Head and Neck Squamous Cell Carcinoma
Purpose: To evaluate the efficacy of low-dose pulsed radiation therapy (PRT) in 2 head and neck squamous cell carcinoma (HNSCC) xenografts and to investigate the mechanism of action of PRT compared with standard radiation therapy (SRT). Methods and Materials: Subcutaneous radiosensitive UT-SCC-14 and radioresistant UT-SCC-15 xenografts were established in athymic NIH III HO female mice. Tumors were irradiated with 2 Gy/day by continuous standard delivery (SRT: 2 Gy) or discontinuous low-dose pulsed delivery (PRT: 0.2 Gy × 10 with 3-min pulse interval) to total doses of 20 Gy (UT14) or 40 Gy (UT15) using a clinical 5-day on/2-day off schedule. Treatment response was assessed by changes in tumor volume, {sup 18}F-fluorodeoxyglucose (FDG) (tumor metabolism), and {sup 18}F-fluoromisonidazole (FMISO) (hypoxia) positron emission tomography (PET) imaging before, at midpoint, and after treatment. Tumor hypoxia using pimonidazole staining and vascular density (CD34 staining) were assessed by quantitative histopathology. Results: UT15 and UT14 tumors responded similarly in terms of growth delay to either SRT or PRT. When compared with UT14 tumors, UT15 tumors demonstrated significantly lower uptake of FDG at all time points after irradiation. UT14 tumors demonstrated higher levels of tumor hypoxia after SRT when compared with PRT as measured by {sup 18}F-FMISO PET. By contrast, no differences were seen in {sup 18}F-FMISO PET imaging between SRT and PRT for UT15 tumors. Histologic analysis of pimonidazole staining mimicked the {sup 18}F-FMISO PET imaging data, showing an increase in hypoxia in SRT-treated UT14 tumors but not PRT-treated tumors. Conclusions: Differences in {sup 18}F-FMISO uptake for UT14 tumors after radiation therapy between PRT and SRT were measurable despite the similar tumor growth delay responses. In UT15 tumors, both SRT and PRT were equally effective at reducing tumor hypoxia to a significant level as measured by {sup 18}F-FMISO and pimonidazole.
- OSTI ID:
- 22462377
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 92, Issue 4; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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