Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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