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Mechanism of Action Combidex in MR Imaging
Mukesh Harisinghani, MD
Department of Radiology,
Massachusetts General Hospital
2
Overview
Current limitations for LN staging in cancer
Combidex enhanced MRI Mechanism of action
Fulfills unmet clinical need of staging LN in patientswith known primary cancer
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Why Image Lymph Nodes?
Accurate staging of the primary cancer
Appropriate treatment
Prostate Cancer
LN Positive Treatment changed to non-surgical
Get a sense of the prognosis
Bladder Cancer
Node Negative 10-year survival 57–87%
Node Positive 5-year survival 35–38%
Risk of death increases 20% with each additional + LN
Cheville et al. Cancer 97, 2003.
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Current LN Staging
Non-InvasiveNon-Invasive
ImagingImaging
InvasiveInvasive
Surgical LN Sampling (gold standard)Surgical LN Sampling (gold standard)
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Size Criteria
< 10 mm< 10 mm
< 8 mm< 8 mm
BenignBenign
> 10 mm> 10 mm
> 8 mm> 8 mm
MalignantMalignant
BenignBenign MalignantMalignant
18 mm in short axis 5 mm in short axis
Size criterion is inaccurateSize criterion is inaccurate
Morphology – Fatty Hilum
MalignantMalignantBenignBenign
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Morphology – Central Necrosis
CT in Cervical Cancer
Positive predictive valueof 100% for nodal metastases
Most necrotic nodes haddiameter > 2 cm
Yang et al. AJR 2000;175.
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Pelvic Lymphadenectomy
Pelvic lymph node dissection (PLND) accompanied by frozen section pathological examination
Standard pelvic lymphadenectomyis limited
Extended pelvic lymphadenectomy
Incidence of lymph node metastases increased from 10% to 26.2%
Heidenreich et al. J Urol. April 2002.
Extended lymph node dissection Obturator nerve injury Trauma to major vessels
Narayan et al. Urology 1994;44:519–24.
Frozen section pathologic analysis has false negative rate of 30–40%
Young et al. J Clin Path 52,1999.
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Current Need
Non-invasive techniqueNon-invasive technique that detects andcharacterizes LN with high degreeof sensitivity and specificity
Broad anatomic coverageBroad anatomic coverage for all LN
Combidex(ferumoxtran-10)
NanoparticlesSize: 21 nmR1: 17 mMsec-1R2: 48 mMsec-1
Uptake by normal lymph nodes
Combidex(ferumoxtran-10)
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Technique
1.5 T MR systems using pelvic phasearray coil (Siemens Magnetom, GE Horizon)
Imaging time/sequences (25 minutes/patient) T2 FSE sequences T2* gradient echo sequences 3D gradient echo sequences
Post-processing 3D reconstruction
Pre-contrastPre-contrast Post-contrastPost-contrast
24 hours
20 mm20 mm
Unenhanced MRUnenhanced MR Combidex enhanced MRCombidex enhanced MR
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Clinical Impact
Improved clinical staging
Surgical planning
Radiation therapy planning
Image-guided intervention
COMBIDEX®COMBIDEX®
(ferumoxtran-10)(ferumoxtran-10)