Transcript Imaging modalities in prostate cancer

Imaging modalities in prostate
cancer
Bahjat moussa PGY4 urology
Dr Georges Assaf Moderator
24-04-14
PET in PC patients
• Role of functional imaging
– not well established yet
• The aim of this review
– to offer an overview about the main applications
of choline PET in PC patients
Detection of intra-prostatic cancer
• Use of choline PET/CT for initial diagnosis and
local staging of prostate cancer
– not recommended as a first line screening method
• The only potential application of PET/CT
– increase the detection rate of cancer on repeated
TRUS-guided biopsies
– in patients in which at least 2 inconclusive TRUSguided biopsy have been already performed
Staging
• The use of choline PET/CT for preoperative LN
staging
– showed very contradictory results
– However good specificity and PPV
– limited to patients with very high risk for LN
positive status according to nomograms
• At the present time
– routine clinical use of choline PET/CT cannot be
recommended in staging patients with PC
• A negative Choline PET/CT
– is not sufficient to rule out a lymph-adenectomy
• PET could be useful to exclude from surgery
– patients with high surgical risk in which the
presence of LN lesions were assessed by PET (high
PPV)
• PET/CT showed
– sensitivity 60%
– a much better specificity 97%
Restaging
• Imaging should be able to find the site of
recurrence
– distinguish between local failure and distant
metastasis
Detection of LN and distant recurrence in PC patients
with biochemical recurrence
– significantly high detection rate
– relationship between detection rate and Trigger
PSA values
– a relationship between detection rate and PSA
kinetics
• a crucial role as first diagnostic procedure in patients
who demonstrate a fast growing PSA kinetics and low
Trigger PSA
• In case of slow growing PSA kinetics
– sensitivity of PET does not seems to be so high
– questionable if a PET/CT should be performed as
first imaging procedure
• In case of local relapse
– TRUS and/or pelvic endorectal MR remain the first
procedures
– choline PET/CT could have only a complementary
role to exclude the presence of distant metastasis,
before a local RT salvage treatment
Conclusion
• Use of choline PET/CT for initial diagnosis and
staging
– is not recommended as a first-line method
• Most important application of choline PET/CT
– restaging of the disease in case of biochemical
relapse for the detection of LN and distant
recurrence
Conclusion
• Choline PET/CT
– could play a crucial role as first diagnostic
procedure in PC patients who show a fast growing
PSA kinetics
• The diagnostic evidence is stronger in
restaging than in staging settings
• Proper patient selection
– PSA level
– PSA doubling time
– initial tumor stage
is the key to avoiding FN results up front
• The use of choline PET/CT scanning
– May accurately provide the localisation of the site
of prostate recurrence in a single step
• Choline PET/CT’s detection rate of recurrences
rises together with the increase in PSA serum
value
• According to the current available data
– the routine use of choline PET/CT scanning cannot
be commonly recommended for PSA values <1
ng/ml
• Independent predictors of positive choline
PET/CT
– PSA DT
– previous biochemical failure
– locally advanced tumour
– pathologic lymph node disease at initial staging
• Can choline positron emission
tomography/computed tomography help
individualise treatment decisions?
• Confirmatory data are still needed
• Choline PET/CT imaging has recently been
proposed to allow new opportunities for
individualised treatment on recurrent lesions
after radical treatment for PCa
• Patients with local recurrence after RP
– best treated by salvage RT when the PSA serum
level is <0.5 ng/ml
• Choline PET/CT scanning is not commonly
useful in this scenario
– low detection rate for PSA serum values <1 ng/ml
• Choline PET/CT scanning, providing wholebody information on Pca spread
– may be useful in selecting patients to be referred
to local treatment
– by distinguishing those patients with local
recurrences from those who present with distant
metastases
Salvage lymphadenectomy
• Choline PET/CT scanning
– very useful for indicating the presence of lymph
nodal involvement
• in patients who present with a progressive PSA increase
after radical treatment
• it provides a basis for further treatment decisions
Role of MRI
According to the guidelines
PSA increase over a threshold of 0.2 ng/ml later
than 6 to 12 months after radical prostatectomy
• suggests treatment failure with a high risk of local
recurrence
increase within a shorter period
• correlates with distant metastasis
For EBRT; biochemical failure
• increasing PSA level after a nadir level
Transrectal ultrasound-guided biopsy
• The current reference standard for the
detection of local recurrence in patients with
biochemical failure
• Invasive
• may fail to depict some tumours because only
a small fraction of the gland is sampled
Computed tomography
• Not widely used for the detection of local
recurrence
– low accuracy in the differentiation of local
recurrence from postsurgical scarring
MRI
• MRI can accurately detect local recurrences
after EBRT and radical prostatectomy
– DCE MRI is particularly accurate
• The addition of 1H-MRSI to DCE MRI
– significantly improve the diagnostic accuracy of
local prostate cancer recurrence
MRI
– usually used for local staging in intermediate and
high risk patient groups
– useful in low risk patients as well
– sensitivity and specificity 75% and 95%
respectively
• Functional MRI techniques
– diffusion-weighted magnetic resonance (DW-MR)
– dynamic contrast-enhanced (DCE-MR)
– MR spectroscopy
• Conventional MRI
– only able to diagnose metastatic lymph nodes
bigger than 10 mm
• A newly invented MRI technique lymphotropic
superparamagnetic nanoparticles
– detect occult lymph node metastasis smaller than
10 mm
– 100% sensitivity and 95.7% specificity
MR Spectroscopy
• Measures the level of specific metabolites in
the prostate gland
– Combination of choline and creatine is measured
in MRS
– The other metabolite that MRS measures is citrate
• accumulate in peripheral zone
• high in normal prostate tissue but decreases in
malignant tissues
MR Spectroscopy
• The ratio of Cho+Cr/Ci
– used for evaluation of prostate cancer
• Higher ratio
– in favor of higher risk of malignancy
– more than 0.75 is considered as significant and is
consistent with prostate cancer
MR Spectroscopy
• More accurate in detecting prostate cancers
with high grade of malignancy
– in low grade cancers its accuracy is limited
Dynamic Contrast Study
• Works based on neo angiogenesis in tumor
cells
• Angiogenesis rate is high
– newly made vessels have low integrity in their wall
– more permeable than normal vessels
Dynamic Contrast Study
• Gadolinium contrast agent is injected
– then serial 3D T1- weighted images are obtained
• Fast leakage of contrast agent from leaky
tumoral vasculature
– early enhancement of tumoral tissue in T1 weighted MRI
– early wash out of contrast agent are seen in
prostate cancer
Diffusion Weighted Imaging
• Works based on water molecules movements
– Water molecules movement decrease in a high
cellular environment
– so diffusion become lower
• Sensitivity and specificity of DWI when added
to T2-Weighted MRI for detecting prostate
cancer is about 84% and 87% respectively
MRI Ability to Detection Bony
Metastasis
• The most sensitive and specific technique in
detecting bony metastasis
Whole-body DW imaging
• The most newly MRI technique
• Very helpful in detection of prostate cancer
and its metastasis as well as post cancer
therapy fallow up
Local Staging of Prostate Cancer
• High resolution MR images
– especially with the use of endorectal coil
– can show with high accuracy
• whether the tumor is confined to prostate gland or
there is extra capsular extension
• The gold standard approach for:
– Diagnosis
– Staging and management of prostate cancer
Is using 1.5 T MR machines with both endorectal
and pelvic phased-array coils
Evaluation of Local Recurrence After
Treatment
• MR spectroscopy detects recurrence after
radical prostatectomy
– 84% and 88% sensitivity and specificity
respectively
• DWMRI
– capable to detect cancer recurrence after radical
prostatectomy in patients that conventional MRI
has missed recurrence
• DW-MR imaging alone shows low sensitivity in
cancer recurrence detection after
radiotherapy (25%)
• In combination with T2-Weighted MRI
– sensitivity increases to 62%
– Specificity in both condition is acceptable (92% vs
97%)
High resolution Multiparametric MR
imaging
• includes:
– regular T1 weighted and T2 weighted images
– dynamic contrast-enhanced MRI
– diffusion weighted imaging
– MR spectroscopy
High resolution Multiparametric MR
imaging
• Obtained in 1.5 T MR machines with simultaneous use
of pelvic and endorectal coils
– best imaging modality in prostate cancer
• useful for
– detection and local staging of prostate cancer
– follow-up of patients after radical prostatectomy or
radiation therapy
– detection of skeletal metastasis
– targeting biopsies in patients highly suspicious of prostate
cancer but with previous negative TRUS guided biopsies
References