Imaging modalities in prostate cancer

Bahjat moussa PGY4 urologyDr 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 TRUS-

guided 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 whole-body 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