A new class of effective therapy for men with metastatic castration-resistant prostate cancer

Global news: A new class of effective therapy for men with metastatic castration-resistant prostate cancer

PROFESSOR MICHAEL HOFMAN

Each year The American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium is held. It is the preeminent genitourinary oncology event, co-developed by committees with representatives from the American Society of Clinical Oncology (ASCO), the American Society for Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO). The Symposium offers focused educational sessions and abstract presentations organised into each below the belt cancer type.

This year ANZUP reported the results of its “TheraP” (ANZUP 1603) clinical trial at this event.

TheraP is the first randomised trial comparing 177LuPSMA-617 (Lu-PSMA), a novel radioactive treatment, to the current standard-of-care chemotherapy called cabazitaxel for men with metastatic castration-resistant prostate cancer. These men had disease that had already progressed after standard chemotherapy.

This unique treatment involves first “mapping” the cancer with a PET scan, then treatment with a radioactive substance Lutetium-177 attached to a similar molecule as used for the PET scan. This novel dual approach of imaging and treatment is called “theranostics.”

The primary endpoint of the study was to compare the effects of the two treatments on change in PSA, a blood biomarker of prostate cancer. A favourable response was demonstrated, defined by reduction of PSA by 50% or more. This occurred in 66% of men assigned to receive 177Lu-PSMA-617 compared to 37% with cabazitaxel chemotherapy.

In addition, 177Lu-PSMA-617 also delayed the time to progression. This is defined by a rise in PSA or progression on CT or bone scans. Patients assigned to receive 177Lu-PSMA-617 were 37% less likely to progress. At 12 months, 19% of men assigned to 177Lu-PSMA-617 had not progressed, compared to 3% with cabazitaxel. Tumour shrinkage on CT scanning occurred in 49% assigned to receive 177Lu-PSMA 617 compared to 24% with cabazitaxel.

The 177Lu-PSMA-617 resulted in less side effects to patients than cabazitaxel. Severe adverse effects reported by physicians occurred in 33% with 177Lu-PSMA-617 compared to 54% with cabazitaxel. Patients reported less symptoms with 177Lu-PSMA-617 including hair loss, diarrhoea, fatigue, insomnia, dizziness, urinary symptoms, sore hands/feet and skin rash.

Study Chair Prof. Michael Hofman, of the Peter MacCallum Cancer Centre, said “The theranostics imaging test enables selection of men likely to benefit, whilst the treatment kills tumours and spares normal tissues. This new class of targeted treatment offers men quality of life and better response rates than chemotherapy. It is likely to be available globally in the next 2 years.”

“TheraP is the first trial in the world comparing Lu-PSMA to an active and effective treatment, and has provided evidence that Lu-PSMA might be a good alternative option to chemotherapy for men with advanced and pre-treated prostate cancer. This is the culmination of years of work by a large team of clinicians, researchers, and community representatives,” said ANZUP Chair Professor Ian Davis.