Prospective, Multicenter Validation Study of Magnetic Resonance Volumetry for Response Assessment After Preoperative Chemoradiation in Rectal Cancer: Can the Results in the Literature be Reproduced?

M.H. Martens*, M.M. van Heeswijk, J.J. van den Broek, S.X. Rao, V. Vandecaveye, R.A. Vliegen, W.H. Schreurs, G.L. Beets, D.M. Lambregts, R.G.H. Beets-Tan

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


PURPOSE: To review the available literature on tumor size/volume measurements on magnetic resonance imaging for response assessment after chemoradiotherapy, and validate these cut-offs in an independent multicenter patient cohort. METHODS AND MATERIALS: The study included 2 parts. (1) REVIEW OF THE LITERATURE: articles were included that assessed the accuracy of tumor size/volume measurements on magnetic resonance imaging for tumor response assessment. Size/volume cut-offs were extracted; (2) Multicenter validation: extracted cut-offs from the literature were tested in a multicenter cohort (n=146). Accuracies were calculated and compared with reported results from the literature. RESULTS: The review included 14 articles, in which 3 different measurement methods were assessed: (1) tumor length; (2) 3-dimensonial tumor size; and (3) whole volume. Study outcomes consisted of (1) complete response (ypT0) versus residual tumor; (2) tumor regression grade 1 to 2 versus 3 to 5; and (3) T-downstaging (ypT<cT). In the multicenter cohort, best results were obtained for the validation of the whole-volume measurements, in particular for the outcome ypT0 (accuracy 44%-80%), with the optimal cut-offs being 1.6 cm(3) (after chemoradiation therapy) and a volume reduction of Delta80% to 86.6%. Accuracies for whole-volume measurements to assess tumor regression grade 1 to 2 were 52% to 61%, and for T-downstaging 51% to 57%. Overall accuracies for tumor length ranged between 48% and 53% and for 3D size measurement between 52% and 56%. CONCLUSIONS: Magnetic resonance volumetry using whole-tumor volume measurements can be helpful in rectal cancer response assessment with selected cut-off values. Measurements of tumor length or 3-dimensional tumor size are not helpful. Magnetic resonance volumetry is mainly accurate to assess a complete tumor response (ypT0) after chemoradiation therapy (accuracies up to 80%).
Original languageEnglish
Pages (from-to)1005-1014
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number5
Publication statusPublished - 1 Jan 2015

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