Detection of the index tumour and tumour volume in prostate cancer using T2-weighted and diffusion-weighted magnetic resonance imaging (MRI) alone.
OBJECTIVE
To examine the performance of T2-weighted (T2W) and diffusion-weighted (DW) magnetic resonance imaging (MRI) for detecting the index tumour in patients with prostate cancer and to examine the agreement between MRI and histology when assessing tumour volume (TV) and overall tumour burden.


METHODS
The study included 199 consecutive patients with biopsy confirmed prostate cancer randomised to MRI before radical prostatectomy from December 2009 to July 2012. MRI-detected tumours (MRTs) were ranked from 1 to 3 according to decreasing volume and were compared with histologically detected tumours (HTs) ranked from 1 to 3, with HT 1 = index tumour. Whole-mount section histology was used as a reference standard. The TVs of true-positive MRTs (MRTVs 1-3) were compared with the TVs found by histology (HTVs 1-3). All tumours were registered on a 30-sector map and by classifying each sector as positive/negative, the rate of true-positive and -negative sectors was calculated.


RESULTS
The detection rate for the HT 1 (index tumour) was 92%; HT 2, 45%; and HT 3, 37%. The MRTV 1-3 vs the HTV 1-3 were 2.8 mL vs 4.0 mL (index tumour, P < 0.001), 1.0 mL vs 0.9 mL (tumour 2, P = 0.413), and 0.6 mL vs 0.5 mL (tumour 3, P = 0.492). The rate of true-positive and -negative sectors was 50% and 88%, κ = 0.39.


CONCLUSIONS
A combination of T2W and DW MRI detects the index tumour in 92% of cases, although MRI underestimates both TV and tumour burden compared with histology.
Department of Radiology and Nuclear Medicine, Oslo University Hospital, Aker, Norway.
Erik
E
Rud
Department of Pathology, Oslo University Hospital, Ullevål, Norway.
Dagmar
D
Klotz
Department of Urology, Oslo University Hospital, Aker, Norway.
Kristin
K
Rennesund
Department of Urology, Oslo University Hospital, Aker, Norway.
Eduard
E
Baco
Department of Urology, Oslo University Hospital, Aker, Norway.
Viktor
V
Berge
Unit of Biostatistics and Epidemiology, Oslo University Hospital, Ullevål, Norway.
Diep
D
Lien
Department of Pathology, Oslo University Hospital, The Norwegian Radiumhospital, Oslo, Norway.
Aud
A
Svindland
Department of Urology, Oslo University Hospital, Aker, Norway.
Eskild
E
Lundeby
Department of Urology, Oslo University Hospital, Aker, Norway.
Rolf E
RE
Berg
Department of Urology, Oslo University Hospital, Aker, Norway.
Lars M
LM
Eri
Department of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway.
Heidi B
HB
Eggesbø
D000368:Aged; D038524:Diffusion Magnetic Resonance Imaging; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D047368:Tumor Burden
MRI; diffusion-weighted MRI; index tumour; prostate cancer; tumour volume