PSMA

PSMA is a cell surface antigen expressed  to a limited degree on certain normal cells.

It is a neurotransmitter in the brain and a folate hydrolase receptor in the gut.

It allows folate to be transported to the circulation after ingestion of food.

It is over expressed in prostate cancer with an increase of 1000 fold or even 10,000 fold compared with normal tissues.

PSMA expression decreases three to tenfold in the presence  of androgen.

High expression of PSMA in metastatic castration resistant prostate cancer independently is associated with reduced survival.

In the setting of prostate cancer PSMA expression generally increases along with the cancer grade, and it also increases following hormonal therapy.

PSMA expression tends to be higher  in metastatic than  in primary prostate tumors.

PSMA is not present in 100% of prostate cancers or in 100% of cells within a prostate tumor.

Prostate biopsy and autopsy studies by PSMA imaging revealed positivity in approximately 90% of prostate cancer sites.

PSMA levels are highly linked to the androgen receptor pathway.

PSMA levels increase as  resistance to hormonal therapy develops.

 Prostate tumors that are not driven by the androgen receptor such as neuroendocrine, small cell and undifferentiated prostate cancers are commonly PSMA negative.

PSMA traces utilize Gallium and fluorine-18 that bind PSMA receptor.

PSMA luteum radionuclide therapy is available for Prostate cancer.

These tracers are used with positron emission tomography/computer tomography scan in prostate cancer.

Imaging and biopsy are the main ways to establish PSMA positivity.

Indium  111 capromab, Ga 68, F-18 our approved imaging modalities for localization of PSMA positive tumors.

PSMA PET/CT has a high sensitivity and high specificity in evaluating prostate cancer compared with conventional imaging such as CT, bone scan, and MRI.

The radiotracer is taken up by the prostate cancer, and allows the identification of disease in the prostate gland, lymph glands and invested metastatic sides.

PSMA PET/CT can detect disease as small as 3 mm in the lymph nodes, which is not possible with conventional imaging.

PSMA/CT scans provide high specificity and benign lesions do not light up.

PSMA-based imaging is not 100% sensitive and can produce false negative results.

PSMA PET-CT/MRI does not reliably detect nodal metastasis measuring less than 5 mm.

With PSMA/CT is possible to visualize abnormalities in the prostate bed and local regionally to us lymph nodes and distant spread evenly when PSA levels are extremely low.

Can be utilized to determine the response to systemic therapy for prostate cancer.

More than 95% of high-risk prostate cancers have high PSMA expression.

5-10% of prostate cancer is denied express detectable amounts of PSMA.

PSMA expression can change as the disease of prostate cancer progresses, particularly after multiple regimens of treatment.

With increasing poorly differentiated tumor the PSMA expression can be lost and will not be positive on scan.

PSMA PET/CT can be used to identify sites of biochemical recurrence in which patients have small volume disease or oligometastases.

Metastatic prostate cancer with a high expression of PSMA is likely to respond to PSMA-directed therapy.

Lu-PSMA-617 delivers beta-particle radiation selectively to PSMA positive cells and the surrounding micro environment.