Final version prostate ca MR

Advances in MR Imaging of PROSTATE CANCER Demetri Papadatos, MD, FRCPC Abdominal Imaging Radiologist Director, Abdominal Imaging Fellowship Director, Percutaneous Radiofrequency Ablation The Ottawa Hospital PROSTATE CANCER  Most common malignancy of men in US after skin cancer  At autopsy, prostate cancer is found in   30% of men at age 50 almost 90% at age 90  About one in six men will be diagnosed with prostate cancer during lifetime  However, only / 34 will die of the disease PROSTATE CANCER  Many cancers are indolent, show no signs of clinical growth  Despite the long latent period, second commonest cause of cancer death in American men over age 55 ETIOLOGY - RISK FACTORS  All men are at a risk of developing prostate cancer  Age : Greatest risk factor risk increasing significantly after 50 yrs  Family history: Men with affected father or brother at increased risk ACA Recommendation to start screening 10 yrs earlier compare to general population  Genetic Factors – abnormal genes in 10 % but genetic testing is not available yet  Race:  more frequent and aggressive in African American men  Environmental and dietary factors HISTOPATHOLOGICAL TYPES  More than 95% of prostatic malignancies are adenocarcinomas  Rarely, a squamous or transitional cell neoplasm  Very rarely sarcoma SCREENING  Routine Screening is offered Men > 50 yrs  With a life expectancy of at least 10 yrs   Screening consists of : Digital rectal examination  Serum PSA levels  PSA (Prostatic Specific Antigen)  Secreted into blood stream by the prostate gland  It’s routine use for screening has lead an exponential rise in prostate cancers, which are being detected much earlier  Elevated PSA = non specific  Also seen in benign prostatic hypertrophy (BPH) and prostatitis (benign conditions) If PSA elevated  Repeat PSA level a few weeks later when probable occult prostatitis has resolved  Calculate PSA Density (PSA/gland volume) increases PSA specificity transrectal ultrasound (TRUS) = gland volume + ? Nodules  Free PSA increases PSA specificity    Low in CA Elevated in benign prostatic hypertrophy (BPH) If < 25 % of PSA is free – worrisome for cancer DIAGNOSIS  Diagnosis of prostate carcinoma is usually made by TRUS-guided core biopsy  However, can have +ve/rising PSA but –ve biopsies  Dilemma  Do these patients have prostate cancer ???  If so, why are the biopsies negative ??? Transrectal Ultrasound (TRUS) and Biopsy (Bx)  TRUS can assess gland volume (PSAD) and detect nodules  However, nodules may or may not represent cancer  Therefore, perform multiple biopsies in attempt to find the suspected cancer  TRUS is used to guide needle placement for biopsies TUMOR VOLUME TUMOR VOLUME  There is an association between primary tumor volume and local extent of disease, progression, and survival  A review of a large number of prostate cancers in surgical and autopsy specimens showed    Capsular penetration Seminal vesicle invasion and Lymph node metastases usually found only with tumors larger than 1.4 cc TUMOR VOLUME  Another study - ECE in 18 % with vol < cc 79% with volume > cc  Tumor volume – significant predictor of ECE  Bx, TRUS and T2-MRI disappointing in volume estimation  MRS provides more accurate volume estimation ROLE OF SPECTROSCOPY IN ESTIMATING TUMOR VOLUME  Relative tumor volume is determined on MRS ( counting the voxels containing abnormal spectra )  Improves Dx of ECE for both experienced and less experienced reader  Decrease inter observer variability – further studies required to assure improvement in the performance of truly inexperienced reader MR SPECTROSCOPY - MRS  Technically demanding and time consuming  Improvement in diagnostic accuracy and staging have been reported but not proved in multi institutional trials  ACR clinical trial is currently underway  Currently cannot be considered as routine diagnostic tool Diffusion-weighted Imaging (DWI)  Diffusion is the process of thermally induced random molecular displacement – Brownian motion  Diffusion properties of tissues are related    Amount of tissue water Tissue permeability Cancer tends to have restricted diffusion due to   High cell densities Abundant intracellular membranes DWI ADVANTAGES  Short acquisition time  High contrast resolution between tumor and normal tissue  No need for endorectal Coil DISADVANTAGES  Poor spatial resolution  Potential risk of image distortion by post biopsy Hg LOCAL STAGING N STAGING ABNORMAL NODES  Early metastases can occur in small nodes  Size and shape of nodes inaccurate for staging  ABNORMAL NODES  Rounded configuration  Short axis > 10 mm if oval, > mm if round  T1 OR T2 SI – not helpful  Enhancement suggestive of metastatic lymph node SHORTCOMINGS- NODAL STAGING  Normal sized nodes - contain cancer as micro metastases  Enlarged nodes may be reactive DETECTION OF ABNORMAL LYMPH NODES  Neither CT nor MRI is accurate as laparoscopic nodal dissection  Initial step prior to radical prostatectomy remains nodal dissection  MR is at least as accurate as CT in nodal staging  If good chance the prostate cancer has already spread to the lymph nodes laparoscopic lymph node dissection is a minimally invasive procedure to begin with Lymphotropic Nanoparticles        ULTRASMALL SUPER PARAMAGNETIC MR contrast agents taken up by macrophages Distributes to LNs throughout the body Injected intravenously and imaged 24 hrs later +++ susceptibility effect on T2* MR images Cannot enter tumor (no macrophages) Can differentiate normal/reactive lymph nodes from malignant ones Iron based contrast agents not approved by FDA (Ferumoxtran-10) Future trends  3T MRI       Increased SNR Increased spatial resolution ? Assessment of microscopic disease ? Need for Endorectoil Coil Standardized technique for CE-MRI with availability of vendor software Approval of Lymphotropic Nanoparticles for accurate nodal staging Thanks to: Arifa Sadaf Radiology, Radiographics and AJR Researchers who develop Prostate MR Thank You ... Endorectal Coil MRI T2 imaging (high sensitivity) and add:  Contrast-enhanced MRI (CE-MRI)  MR Spectroscopic Imaging (MRSI)  Diffusion-weighted MRI (DWI) DYNAMIC CONTRAST ENHANCED MRI – DCE MRI WHY... commonest cause of cancer death in American men over age 55 ETIOLOGY - RISK FACTORS  All men are at a risk of developing prostate cancer  Age : Greatest risk factor risk increasing significantly... cancer DIAGNOSIS  Diagnosis of prostate carcinoma is usually made by TRUS-guided core biopsy  However, can have +ve/rising PSA but –ve biopsies  Dilemma  Do these patients have prostate cancer