Download PET Tracers in Prostate Cancer

PET Tracers in Prostate Cancer
Ga-68 PSMA – The new kid on the block.
Prostate Specific Membrane Antigen (PSMA) is a type II membrane
glycoprotein. Nearly all prostate cancers over-express PSMA compared
with benign tissue. The expression increases with tumour aggressiveness,
metastatic disease and disease recurrence. It is also expressed in some other
tumours including clear cell RCC, some transitional cell cancers, colon cancer
and in tumour neovasculature.
The PET tracers target the extra-cellular moiety of PSMA and the most
commonly used is 68Ga(HBED-CC), an extra-cellular PSMA inhibitor. This
demonstrates good imaging characteristics, with high tumour to background
ratios, enabling detection of small volume disease.
Example 1: Ga-68 PSMA PET scan showing bony
metastases and a right iliac nodal met.
(Example from Siemens)
The most utilised role is in the detection of tumour recurrence post surgery,
with rising PSA. Detection rate of up to 73% for PSA between 0.5 and 1.0 and
> 97% if PSA greater than 2(1). It has a high sensitivity for pathological lymph
nodes, which are not enlarged on structural imaging and also able to screen
the body for bony metastases. The role in initial staging of high risk patients
is still being evaluated, as is guiding biopsy sites and in radio-guided surgical
excision of metastases.
Example 2: Ga-68 PSMA avid metastatic left internal iliac node
F-18 FDG PET
This is the standard PET tracer for use in Oncology. Uptake in tumours is related to glucose metabolism. It has not been
considered for routine use in prostate cancer imaging because many prostate cancers are characterised by slow glycolysis
and low FDG avidity, with significant overlap between prostate cancer and benign prostate hyperplasia. Also, significant
renal excretion of FDG and prominent bladder activity may obscure the prostate and adjacent pelvic nodal region.
It is probably not as sensitive as conventional bone scans in detecting bony metastases but is better at differentiating between
active and quiescent disease. It is a good guide to tumour aggressiveness, as only the higher grade tumours will be FDG avid. A
number of studies have highlighted the value of FDG PET/CT in the staging and
restaging of the more aggressive prostate cancers, with a Gleason score of 7 or
more. One study showed a sensitivity of 80% and a PPV of 87% for detection
of PC with Gleason score of 7 or more, in men who present with more than
an intermediate risk of PC based on elevated PSA levels(2). In several other
small studies in this patient group, PET detected 75% of histologically proven
metastatic lymph nodes, compared with 0% for CT(3) and in a retrospective
study of 91pts, PET detected local or systemic recurrence in 31%(4).
Example 4: Newly diagnosed prostate
cancer. Gleason score 8.
? cT3. For further staging.
Focal FDG activity seen in right prostatic
bed, corresponding with the site of the
known tumour on MRI.
Example 3: F-18 FDG PET Scan showing a T4 metastasis,
with low-grade FDG activity in a left inguinal node and
prostate bed. Image from JMIRO 54 (2010) 325–332,
(Courtesy Prof R Hicks)
Comprehensive care. Uncompromising quality.
drjones.com.au
DJPREF0067_Oct15
References: 1. Eiber et al, J Nucl Med 2015;56:668-674); 2.Minamimoto et al, Ann Nucl Med. 2011;25:21-27; 3. Liu, EMJ Oncol. 2013;1:161-67;
4. Schoder H et al, Clin Cancer Res. 2005;11:4761-9
PET Tracers in Prostate Cancer
F-18 FDG
F-18 NaF
F-18 Choline
Ga-68 PSMA
110 minutes
110 minutes
110 minutes
68 minutes
Bone & soft tissue
Bone only
Bone & soft tissue
Bone & soft tissue
Dependent on level of
tumour glycolysis
Level of osteoblastic activity
(same as bone scan)
Increased cell
membrane metabolism,
choline use and CK
expression
Over-expression of
PSMA on tumour cells
Routine
Trial only
No
From October 2015
No **
No
No
No
No - only those with
more aggressive PC,
with Gleason Score > 7
Yes
Yes
Yes
Potentially in more
aggressive PC, with
Gleason Score > 7
Yes - only bone
metastases
Yes - higher risk patients
Yes +/- assist in
identifying higher grade
of primary site to biopsy
Yes - in more
aggressive PC, with
Gleason Score > 7,
especially if higher PSA
Yes - bone only
Yes - detection rate
40-60% if PSA < 3
Yes - high sensitivity,
specificity and low PSA
levels
Half-life
Sites of detection
Mechanism of action
Availability
Medicare rebate for
prostate cancer
Suitable for all patients
Role in staging
Role in restaging/
biochemical recurrence
**Can obtain Medicare benefit if history of head and neck cancer, solitary pulmonary nodule, melanoma or colon cancer.
Other Urological services available:
MRI PROSTATE:
Available at St Andrew’s Hospital, Kurralta Park, Southern Specialist Centre
and Mt Barker Central.
CT UROGRAM:
Non contrast and post contrast imaging available at all metro and rural clinics.
(same day workups available for rural patients)
FLASH CT:
Low dose imaging and stone characterisation at Calvary Wakefield and
St Andrew’s Hospitals.
For further information on PET imaging or bookings,
Kurralta Park Clinic (Tennyson Centre) 520 South Road, Kurralta Park
Comprehensive care. Uncompromising quality.
DJPREF0067_Oct15
Ph: 1300 435 566
drjones.com.au