Optimal Timing for Assessment of Tumor Response to Neoadjuvant Chemoradiation in Patients With Rectal Cancer: Do All Patients Benefit From Waiting Longer Than 6 Weeks?
- Department of Gastroenterology, Colorectal Surgery Division, University of Sao Paulo School of Medicine, Sao Paulo (Brazil)
- Angelita and Joaquim Gama Institute, Sao Paulo (Brazil)
- Department of Radiology, Nuclear Medicine Division, University of Sao Paulo School of Medicine, Sao Paulo (Brazil)
Purpose: To estimate the metabolic activity of rectal cancers at 6 and 12 weeks after completion of chemoradiation therapy (CRT) by 2-[fluorine-18] fluoro-2-deoxy-D-glucose-labeled positron emission tomography/computed tomography ([{sup 18}FDG]PET/CT) imaging and correlate with response to CRT. Methods and Materials: Patients with cT2-4N0-2M0 distal rectal adenocarcinoma treated with long-course neoadjuvant CRT (54 Gy, 5-fluouracil-based) were prospectively studied ( (ClinicalTrials.org) identifier (NCT00254683)). All patients underwent 3 PET/CT studies (at baseline and 6 and 12 weeks from CRT completion). Clinical assessment was at 12 weeks. Maximal standard uptake value (SUVmax) of the primary tumor was measured and recorded at each PET/CT study after 1 h (early) and 3 h (late) from {sup 18}FDG injection. Patients with an increase in early SUVmax between 6 and 12 weeks were considered 'bad' responders and the others as 'good' responders. Results: Ninety-one patients were included; 46 patients (51%) were 'bad' responders, whereas 45 (49%) patients were 'good' responders. 'Bad' responders were less likely to develop complete clinical response (6.5% vs. 37.8%, respectively; P=.001), less likely to develop significant histological tumor regression (complete or near-complete pathological response; 16% vs. 45%, respectively; P=.008) and exhibited greater final tumor dimension (4.3 cm vs. 3.3 cm; P=.03). Decrease between early (1 h) and late (3 h) SUVmax at 6-week PET/CT was a significant predictor of 'good' response (accuracy of 67%). Conclusions: Patients who developed an increase in SUVmax after 6 weeks were less likely to develop significant tumor downstaging. Early-late SUVmax variation at 6-week PET/CT may help identify these patients and allow tailored selection of CRT-surgery intervals for individual patients.
- OSTI ID:
- 22149673
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 84, Issue 5; Other Information: Copyright (c) 2012 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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