ORLANDO, FL USA (UroToday.com) - Dr. Steven Larson presented work from his group at MSKCC on positron emission tomography (PET) which he is using to identify locally invasive and castration-resistant prostate cancer (CRPC), based on biological rationales. He uses imaging biomolecules, which are fundamental to the prostate cancer state, such as glucose and androgen. He showed that patients with high-grade prostate cancer tend to express the Warburg effect in tumor tissue, which makes 18FDG PET a valid imaging modality. Interestingly, this modality can be used at the time of recurrence, and patients with a PSA > 2.4 ng/mL or a rapidly rising PSa had a high rate of 18FDG-PET-positive studies.
Dr. Larson then reviewed his group’s data on androgen receptor (AR)-based imaging with 18F-DHT, which binds AR with similar kinetics to native androgens. When comparing 18FDG and 18F-DHT in 135 patients in a prospective study, they showed that some patients have uptake of both radiopharmaceuticals within the same metastatic lesions. Patients with uptake of both molecules tended to have a worse prognosis. Interestingly, he used imaging to guide therapy, showing that presence of 18F-DHT-avid lesions tended to be sensitive to enzalutamide, with PET-based complete response on follow up. He also presented his work on imaging PSMA using 89Zr-J591, which is a radiopharmecutical monoclonal antibody. This molecule identifies occult metastatic disease in CRPC patients. 90% of 89Zr-J591-avid bone lesions are seen on conventional CT scan, but about 10% are occult, and this was proven with biopsy of the lesions.
In summary, the MSKCC group has made tremendous strides in non-invasive imaging of advanced prostate cancer patients, and such imaging may be used in lieu of biomarkers to rationally inform clinical treatment decisions.
Presented by Steven M. Larson, MD at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA
Memorial Sloan Kettering Cancer Center, New York, NY USA
Written by Philip Abbosh, MD, PhD, medical writer for UroToday.com
