Radiation Changes Do Not Interfere With Postchemoradiation Restaging of Patients With Rectal Cancer by FDG PET/CT Before Curative Surgical Therapy
- Centre for Molecular Imaging, the Peter MacCallum Cancer Centre, Melbourne (Australia)
- Division of Surgical Oncology, Peter MacCallum Cancer Centre, Melbourne (Australia)
- Division of Radiation Oncology, Peter MacCallum Cancer Centre, Melbourne (Australia)
Purpose: Changes in F-18 fluorodeoxyglucose (FDG) uptake in normal tissues after chemoradiation therapy (CRT) potentially limit the ability of positron emission tomography (PET) to provide early assessment of therapeutic response. This study evaluated whether such changes negatively impact interpretation of posttherapy PET performed within 6 weeks of CRT completion and before definitive surgery in patients with locally advanced rectal cancer. The positive predictive value (PPV) and specificity of post-CRT PET, read clinically, was determined in 63 consecutive rectal cancer patients who had undergone preoperative CRT. Methods and Materials: A schema for identifying and scoring postradiation effects on PET was prospectively defined and applied in a blinded manner. This was compared with initial clinical reporting of response. Histologic assessment of the operative specimens was used as the reference standard. Correlation between clinical proctitis during CRT and radiation changes on subsequent PET was also assessed. Results: Clinical reporting of post-CRT PET yielded a high PPV (94%; 95% confidence interval, 89--100%) but may have been exaggerated by the low prevalence of complete tumor clearance (16%). The specificity was 80% with only two false-positive results. On blinded reading, significant post-CRT effects on PET were recorded in 4 of 63 patients (6% 95% confidence interval, 0-13%), but pattern recognition converted both false-positive PET results to a complete metabolic response. Clinical CRT proctitis was not correlated with PET findings. Conclusion: Postradiation effects do not appear to significantly compromise the interpretation of PET for therapeutic response assessment. The proposed PET pattern of response may further improve the specificity of PET.
- OSTI ID:
- 21276771
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 74, Issue 1; Other Information: DOI: 10.1016/j.ijrobp.2008.06.1944; PII: S0360-3016(08)03048-4; Copyright (c) 2009 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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