What is theranostics?
Managing a disease such as prostate cancer often requires continual tests and treatments. These tests and treatments can have side effects, are often expensive and interrupt daily life. Theranostics is a way to manage diseases like cancer through combining therapy and diagnostics. Indeed, the word theranostics is derived from the words therapy and diagnostic. The diagnostic test helps the clinician determine who might benefit from the therapy and once therapy has commenced, it provides a way to monitor the progress of the patient. Theranostics aim to increase survival, reduce side effects and reduce the overall number of tests and treatments that a patient must undergo.
Theranostics for prostate cancer
A theranostics approach to diagnose and treat prostate cancer requires two things:
- A diagnostic – a way to locate the prostate cancer cells are in the body and monitor any change
- A therapy – a way to kill the prostate cancer cells wherever they are in the body
In our blog earlier this year we reported the outcome of a PCFA funded phase III, multi-centre randomised clinical trial that tested the benefits of PSMA-PET scans for the diagnosis of prostate cancer. This study called ProPSMA was led by researchers from the Peter MacCallum cancer centre and is one of the key studies that has led to the establishment of ProsTIC (Prostate Theranostics and Imaging Centre of Excellence).
The ProPSMA study used PSMA-PET scans to detect prostate tumours that had spread to different parts of the body (metastases). PSMA, short for prostate specific membrane antigen, is a protein found on the surface of prostate cancer cells. A PSMA-PET scan is a very sensitive way of detecting prostate cancer cells. The approach uses a radioactive tracer molecule called Galium-68 linked to a molecule that, when in the body, can find and attach to PSMA on the surface of prostate cancer cells. This causes the cells to light up and be clearly seen on the PET scan (more information about this is in our previous blog).
Researchers conducted the ProPSMA study to determine if PSMA-PET scans were more accurate for detecting metastatic prostate tumours than the more commonly used CT and bone scans. The researchers also wanted to know if the results obtained from a PSMA-PET scan would change treatment decisions and reduce radiation exposure. The trial recruited men diagnosed with high-risk localised disease as determine from their biopsies. The key findings of this study are:
- PSMA-PET scans correctly identified 85% of men with metastatic tumours, compared to only 38% for CT and bone scans
- PSMA-PET scans were more likely to change treatment plans (28% of cases compared to 15% for CT and bone scans).
- Men having PSMA-PET scans had less radiation exposure during their scans than men having CT and bone scans.
- Men having PSMA-PET scans were less likely to have uncertain results from their tests (7% versus 23% uncertain findings from CT and bone scans).
The ProPSMA study showed that PSMA-PET scans are a very sensitive way to diagnose metastatic prostate cancer. You can read more about this study here.
To develop a therapy to combine with the PSMA-PET scan diagnostic, the radioactive tracer molecule was replaced with a radioactive molecule called Lutetium-177 creating a new molecule called 177Lu-PSMA-617 (Lu-PSMA for short). Once in the body, Lu-PSMA travels through the blood, attaches to prostate cancer cells and kills them.
In 2018, researchers from the Peter MacCallum cancer centre published the results of a small phase II single-centre clinical trial called LuPSMA trial that aimed to determine if Lu-PSMA was safe and effective as a treatment for men with metastatic castration-resistant prostate cancer whose disease had progressed after standard treatments. The trial recruited 30 men with metastatic castration-resistant prostate cancer whose disease had progressed after standard treatments including chemotherapy and second-generation androgen deprivation therapies. The results of the study were very promising and include
- PSA levels decreased by at least 50% in 17 of the men (57% of cases)
- Low toxicity – common side effects included dry mouth (87% of cases), nausea (50% of cases) and fatigue (50% of cases). A small number (13%) showed reduced platelet cells in their blood.
- Reduced pain levels
This study paved the way for the Peter MacCallum team to launch the TheraP clinical trial supported by a partnership between PCFA and ANZUP (Australian and New Zealand Urogenital and Prostate Cancer Trials Group). This multi-centre randomised phase II trial recruited 200 men with metastatic castration resistant prostate cancer whose disease had progressed after chemotherapy. The study compared LuPSMA theranostics with cabazitaxel treatment (a standard chemotherapy treatment). The study is still ongoing, but interim results were presented in May at the American Society of Clinical Oncology (ASCO) Annual Scientific Virtual Meeting.
Interim results from TheraP show
- PSA levels decreased by at least 50% in 66% of men on LuPSMA compared to 37% of men on cabazitaxel.
- Different side effects were observed for the different treatment. Only 1 man discontinued LuPSMA treatment compare to 3 men in the cabazitaxel group.
These are very promising results, but we will have to wait for the trial to be completed before we will know if LuPSMA increases overall survival in men with metastatic castration resistant prostate cancer.
What does theranostics mean for Australian men with prostate cancer?
Theranostics for prostate cancer offers new hope to Australian men and families impacted by the disease.
Australia is a world leader in theranostics and the launch of the Prostate Theranostics and Imaging Centre of Excellence (ProsTIC) at the Peter MacCallum Cancer Centre paves the way for theranostics to become standard of care for prostate cancer in the future.
ProsTIC is currently running a number of other clinical trials using LuPSMA, you can find more information on these trials at this link https://www.petermac.org/research/ProsTIC/prostic-clinical-trials.
For more information about ProsTIC is available at https://www.petermac.org/ProsTIC.
You can also watch the recent PCFA webinar called Personalised prostate cancer treatment of the future where Professor Michael Hofman and Professor Declan Murphy discuss theranostics for prostate cancer with PCFA CEO Professor Jeff Dunn AO.
PCFA will continue to advocate for affordable access to new treatments like these and invest in life-saving research to ensure no man dies before his time.