FDG-PET provides the best correlation with the tumor specimen compared to MRI and CT in rectal cancer

J. Buijsen*, J. van den Bogaard, M.H. Janssen, F.C. Bakers, S. Engelsman, M. Ollers, R.G.H. Beets-Tan, M. Nap, G.L. Beets, P. Lambin, G. Lammering

*Corresponding author for this work

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PURPOSE: To compare CT-, MR- and PET-CT based tumor length measurements in rectal cancer with pathology. PATIENTS AND METHODS: Twenty-six rectal cancer patients underwent both MR and PET-CT imaging followed by short-course radiotherapy (RT 5x5Gy) and surgery within 3days after RT. Tumor length was measured manually and independently by 2 observers on CT, MR and PET. PET-based tumor length measurements were also generated automatically using the signal-to-background-ratio (SBR) method. All measurements were correlated with the tumor length on the pathological specimen. RESULTS: CT-based measurements did not show a valuable correlation with pathology. MR-based measurements correlated only weakly, but still significantly (Pearson correlation=0.55resp. 0.57; p<0.001). Manual PET measurements reached a good correlation with pathology, but less strong (Pearson correlation 0.72 and 0.76 for the two different observers) than automatic PET-CT based measurements, which provided the best correlation with pathology (Pearson correlation of 0.91 (p<0.001)). Bland-Altman analysis demonstrated in general an overestimation of the tumor diameter using manual measurements, while the agreement of automatic contours and pathology was within acceptable ranges. A direct comparison of the different modalities revealed a significant better precision for PET-based auto-contours as compared to all other measurements. CONCLUSION: Automatically generated PET-CT based contours show the best correlation with the surgical specimen and thus provide a useful and powerful tool to accurately determine the largest tumor dimension in rectal cancer. This could be used as a quick and reliable tool for target delineation in radiotherapy. However, a 3D volume analysis is needed to confirm these results.
Original languageEnglish
Pages (from-to)270-276
Number of pages7
JournalRadiotherapy and Oncology
Issue number2
Publication statusPublished - Feb 2011


  • PET-CT
  • MR
  • Rectal cancer
  • Automatic contours
  • Pathology correlation

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