Results of a phase I study evaluating the safety and biodistribution of ⁶⁸Ga-THP-PSMA PET/CT in patients with prostate cancer were published in The Journal of Nuclear Medicine (JNM) today.

⁶⁸Ga-THP-PSMA can be manufactured quickly using a ⁶⁸Ga generator and cold-kit vial analogous to procedures widely used for 99mTc radiotracer production, and therefore will enable rapid adoption and may widen the access of PET to prostate cancer patients.

⁶⁸Ga- THP-PSMA offers labelling in less than five minutes at room temperature.

Current alternatives, such as the DOTA or HBED chelator, incorporated in the widely used ⁶⁸Ga- HEBD-PSMA or ⁶⁸Ga-DOTATATE requires pH adjustment, heating and cooling, as well as possible purification, requiring significant manual handling and operator radiation dose or use of an automated synthesiser with the possibility of generating a mixture of compounds.

Data from this trial demonstrates that ⁶⁸Ga-THP-PSMA is comparable with standard of care, with background physiologic uptake was significantly lower with ⁶⁸Ga-THP-PSMA compared to ⁶⁸Ga-HBED-PSMA, whilst not changing the management in these patients, as well as concordance in the number of metastases identified.

"PSMA PET has rapidly emerged as practice changing imaging modality with significant advantages compared to conventional imaging such as CT, MRI or bone scanning” says Associate Professor Michael Hofman, and lead investigator of this study. “⁶⁸Ga-THP-PSMA provides the ability to rapidly manufacture PSMA in the clinic on-demand using a simple kit, and therefore can offer efficiencies to alleviate some of the challenges experienced by clinicians when utilising current alternatives where health services are strained, such as the UK - this may reduce the variation in adoption of this technology across the globe, which is a challenge we face in prostate cancer imaging. This is an important advance in order to make this new scan widely available to men with prostate cancer.”

Fourteen patients with biopsy proven adenocarcinoma of the prostate took part in the study and were split into two groups.

Group A included treatment naïve patients scheduled for surgery (prostatectomy).

Group B observed patients with metastatic prostate cancer (represented by demonstration of at least one unequivocal PSMA-avid focus), and compared ⁶⁸Ga-THP-PSMA PET/CT with standard of care, ⁶⁸Ga-HBED-PSMA-11 PET/CT.

Results demonstrated that ⁶⁸Ga-THP-PSMA can be safely administered, with no adverse events recorded in any patients.

Uptake seen in the prostate on ⁶⁸Ga-THP-PSMA PET/CT correlated with histopathologic PSMA expression seen on pathology finding following prostatectomy, highlighting the ability to non-invasively image prostate cancer directly.

⁶⁸Ga-PSMA positron emission tomography/computed tomography (PET/CT) is a non- invasive diagnostic technique to image prostate cancer with increased prostate-specific membrane antigen expression.

PSMA is a transmembrane protein primarily present in all prostatic tissues. Increased PSMA expression is seen in a variety of malignancies, most notably in prostate cancer. Adenocarcinomas of the prostate demonstrate PSMA expression in the majority of primary and metastatic lesions.

⁶⁸Ga-HBED-PSMA-11 PET/CT has demonstrated clinical utility in both staging of newly diagnosed patients and restaging.

More accurate staging of high risk patients may enable better selection of the most appropriate management strategy and avoid futile locoregional surgery or radiotherapy in patients with metastatic disease.

Professor Prokar Dasgupta, Professor and Chair of Urology at King's College London, Guy's Hospital, King's Health Partners comments, “While imaging such as multiparametric MRI has greatly improved the diagnostic and staging pathway in prostate cancer patients, bone scans to detect distant metastasis can often be inaccurate. PSMA PET scanning is fast becoming the imaging modality of choice in high-risk prostate cancer as well as in patients with recurrent disease. Accurate staging, particularly in patients with metastatic disease is absolutely vital. The challenge we face today lies in the cumbersome production of PSMA PET tracer, and so easy, rapid manufacturing would not only be a significant advance, but would also make such scanning widely available to patients.”

Source: Theragnostics Ltd