AUA 2018: Molecular Imaging in GU Malignancies

San Francisco, CA ( Andrei Iaguru, MD provided an update the status of molecular imaging in GU malignancies. First, he focused on FDA-approved pharmaceuticals. 

1. 18FDG PET – the longest available molecular imaging, it utilized the increased glucose metabolism in cancer cells as a marker of malignancy. Based on NCCN guidelines, it can be used in certain GU malignancies.
- Bladder cancer: may be useful in select MIBC patients and pT3+ patients.
- Penile cancer: consider PET/CT for staging (skull-base to mid-thigh)
- Testicular cancer: in seminoma, particularly in post-chemotherapy setting.

2. 18F-Fluciclovine (Axumin) PET/CT
- FDA approved for biochemical recurrent Prostate cancer
- Uptake not specific for prostate cancer and may be seen in other malignancies/BPH
- It is not perfect, but may be helpful

3. 11C-Choline PET/CT
- Short half-life makes its use limited from a logistical standpoint
- Better at identifying bone mets than soft tissue mets – also in setting of BCR Prostate cancer

Next, he reviewed current research pharmaceuticals. Far and away, the most common is the PSMA PET scan.

- PSMA (prostate specific membrane antigen) – it is not prostate specific, not is it a membrane antigen! Yet, despite the misnomer, it has become an important adjunct – more easily available internationally than in the US. 
- It is increasingly being utilized in all stages of prostate cancer management – but the most common is also in BCR prostate cancer
- Stanford is currently using it in a research protocol for newly diagnosed intermediate risk prostate cancer  as well as in the BCR prostate cancer setting

2. Gastrin-releasing peptide Receptor (GRPR) Imaging in prostate cancer
- GRP-R are overexpressed in many malignancies, including prostate cancer
- As such, Stanford is also assessing this in the biochemical recurrence population
- Initial results demonstrated that it exceeded the detection rate of MRI for oligometastases
- As with other PET imaging modalities, it was PSA dependent – best in PSA > 5.
- Detection rates varied from 42% (PSA 0.2-1.0) to 92% (PSA>5.0).

3. Imaging angiogenesis (Integrin alpha5-beta3)
- Prostate cancer, along with other malignancies, are often very vascular with high degree of angiogenesis
- As such, novel imaging modalities are targeting angiogenesis markers
- These are much earlier in the development pathway

Lastly, he reviewed future directions of molecular imaging.  Theragnostics – the combination of therapy and diagnostics. In this field, a therapeutic agent is linked to the diagnostic marker, thereby carrying the treatment right to the tissue of interest.

1. 177Lu-PSMA radioligand therapy – the best known and published so far. Lutetium is linked to PSMA targeting agents and is taken directly to the tissue. Early reports have been promising with some patients having dramatic response. However, larger series and long-term results are pending.

Further work in this area may help expand treatment options for patients with prostate cancer!

Presented by: Andrei Iaguru, MD, Stanford University, Palo Alto, CA

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA