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?

Rodrigo O. Perez, Angelita Habr-Gama, Guilherme P. São Julião, Joaquim Gama-Rodrigues, Afonso H.S. Sousa, Fabio Guilherme Campos, Antonio R. Imperiale, Patricio B. Lynn, Igor Proscurshim, Sergio Carlos Nahas, Carla Rachel Ono, Carlos Alberto Buchpiguel

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63 Scopus citations


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 ([18FDG]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 18FDG 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.

Original languageEnglish (US)
Pages (from-to)1159-1165
Number of pages7
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number5
StatePublished - Dec 1 2012

All Science Journal Classification (ASJC) codes

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research

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