Prostate tumor delineation using multiparametric magnetic resonance imaging: Inter-observer variability and pathology validation.
OBJECTIVE
Boosting the dose to the largest (dominant) lesion in radiotherapy of prostate cancer may improve treatment outcome. The success of this approach relies on the detection and delineation of tumors. The agreement among teams of radiation oncologists and radiologists delineating lesions on multiparametric magnetic resonance imaging (mp-MRI) was assessed by measuring the distances between observer contours. The accuracy of detection and delineation was determined using whole-mount histopathology specimens as reference.


METHODS
Six observer teams delineated tumors on mp-MRI of 20 prostate cancer patients who underwent a prostatectomy. To assess the inter-observer agreement, the inter-observer standard deviation (SD) of the contours was calculated for tumor sites which were identified by all teams.


RESULTS
Eighteen of 89 lesions were identified by all teams, all were dominant lesions. The median histological volume of these was 2.4cm(3). The median inter-observer SD of the delineations was 0.23cm. Sixty-six of 69 satellites were missed by all teams.


CONCLUSIONS
Since all teams identify most dominant lesions, dose escalation to the dominant lesion is feasible. Sufficient dose to the whole prostate may need to be maintained to prevent under treatment of smaller lesions and undetected parts of larger lesions.
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Peter
P
Steenbergen
Radiation Oncology, University Hospitals Leuven, Department of Oncology, KU Leuven, Belgium.
Karin
K
Haustermans
Pathology, University Hospitals Leuven, Department of Imaging & Pathology, KU Leuven, Belgium.
Evelyne
E
Lerut
Radiology, University Hospitals Leuven, Department of Imaging & Pathology, KU Leuven, Belgium.
Raymond
R
Oyen
Radiology, University Hospitals Leuven, Department of Imaging & Pathology, KU Leuven, Belgium.
Liesbeth
L
De Wever
Radiation Oncology, University Hospitals Leuven, Department of Oncology, KU Leuven, Belgium.
Laura
L
Van den Bergh
Department of Radiation Oncology, University Medical Center Utrecht, The Netherlands.
Linda G W
LG
Kerkmeijer
Department of Radiology, University Medical Center Utrecht, The Netherlands.
Frank A
FA
Pameijer
Department of Radiology, University Medical Center Utrecht, The Netherlands.
Wouter B
WB
Veldhuis
Department of Radiation Oncology, University Medical Center Utrecht, The Netherlands.
Jochem R N
JR
van der Voort van Zyp
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Floris J
FJ
Pos
Department of Radiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Stijn W
SW
Heijmink
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Robin
R
Kalisvaart
Department of Radiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Hendrik J
HJ
Teertstra
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Cuong V
CV
Dinh
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Ghazaleh
G
Ghobadi
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. Electronic address: u.vd.heide@nki.nl.
Uulke A
UA
van der Heide
D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D015588:Observer Variation; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy / Q000601:surgery; D011829:Radiation Dosage
Dose escalation; Inter-observer variability; Multiparametric MRI; Prostate cancer; Radiotherapy; Tumor delineation