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31P magnetic resonance spectroscopy detection of response-predictive adenosine triphosphate decrease in irradiated
P E Sijens1, N J Baldwin, T C Ng
1Magnetic Resonance Research Center, Cleveland Clinic Foundation, Ohio, USA.
Investigative Radiology
|January 1, 1997
Summary
Radiation-induced fibrosarcoma (RIF-1) tumor ATP reduction after x-ray therapy predicts treatment success. Early metabolic shifts in RIF-1 tumors indicate potential treatment efficacy.
Area of Science:
- Biomedical imaging
- Cancer research
- Magnetic resonance spectroscopy
Background:
- Previous phosphorus-31 (31P) magnetic resonance (MR) spectroscopy studies used subcurative doses of x-ray irradiation on RIF-1 tumors.
- A more effective x-ray dose was employed in this study to correlate treatment efficacy with early 31P MR spectral changes.
Purpose of the Study:
- To investigate the correlation between early metabolic changes detected by 31P MR spectroscopy and the efficacy of a curative dose of x-ray irradiation in RIF-1 tumors.
- To determine if early alterations in high-energy phosphates predict tumor response to radiation therapy.
Main Methods:
- Subcutaneous RIF-1 tumors in 60 mice were analyzed using 31P MR spectroscopy.
- Spectroscopy was performed before a single 40 Gy x-ray dose and at multiple time points up to 216 hours post-irradiation.
Main Results:
- Early increases in inorganic phosphate and decreases in adenosine triphosphate (ATP) were observed within 2-12 hours post-irradiation (P < 0.00001).
- These metabolic changes persisted up to 48 hours.
- A reduction in ATP at 48 hours correlated significantly with subsequent tumor shrinkage (r = -0.59; P < 0.00001).
Conclusions:
- Sustained loss of RIF-1 tumor ATP is a predictive marker for radiation therapy efficacy.
- Transient changes in high-energy phosphates do not necessarily indicate cell death or treatment failure.