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

Research output: Contribution to journalArticleAcademicpeer-review

32 Citations (Scopus)


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

Cite this