A Peter Mac clinical trial using a highly advanced, single-dose radiotherapy treatment has halted the spread of prostate cancer in some men, delaying the need for conventional lifelong hormone therapy.
The POPSTAR trial, led by Associate Professor Shankar Siva, involved patients whose prostate cancer had limited spread (one to three additional sites) and who would typically be put on lifelong hormone therapy. Side-effects of these testosterone-blocking treatments include menopause-like symptoms, such as hot flushes, loss of libido and longer-term bone issues like osteoporosis.
In this study, 33 trial patients were given a high precision, focused dose of stereotactic ablative body radiotherapy (SABR) - a technique that delivers radiotherapy with pinpoint accuracy - to each tumour site. The men were subsequently monitored for two years.
The prospective clinical trial was designed and conducted at Peter Mac from 2012-2016, and the results are published today in the journal European Urology.
“It’s just a simple outpatient day visit for about an hour to have each SABR treatment and that's it,” says Assoc Prof Siva.
“Men may then go for two years or more without having any additional treatment and the need for hormone therapy is delayed.
“About half of the patients in the trial didn't need hormone therapy at two years and, in about a third, the cancer didn't come back during the study period at all.”
The results suggest that this approach is safe, very well tolerated and effective for the targeted tumours. Overall 93 per cent of the treated cancer spots were controlled with the radiation treatment.
Importantly, quality of life was assessed with questionnaires and was found to be maintained at pre-treatment levels with this strategy. After a single SABR session to each cancer spot, 48 per cent of men did not require hormone therapy at 2 years, and in over a third of patients (39 per cent) the cancer did not progress.
“What we’ve found is that SABR can be a highly effective strategy in select men with limited spread of advanced prostate cancer, and we need further studies to better understand which men will best suited to this approach,” Assoc Prof Siva says.
“Ultimately our hope is to delay lifelong hormone therapy, and its potential side-effects, with a once-off SABR treatment as this would represent a major quality-of-life improvement for these men, and a real advance in the way we treat prostate cancer.”
POPSTAR trial patient Tony McDonnell, 77, was diagnosed with prostate cancer in 2011 and was placed on hormone treatment before he joined the trial in 2013.
He received a single dose of SABR radiation treatment to his tumour sites and he is no longer on hormone therapy and his secondary spots of cancer have disappeared.
"I used to get hot flushes on the hormone treatment - especially at night - but not anymore," says Tony.
Work is now underway on an international randomised clinical trial in collaboration with the UK. This larger study will investigate if this SABR technique will result in an extension of life in patients with limited spread (one to three additional sites) of advanced prostate cancer.
The paper is titled “Stereotactic Ablative Body Radiotherapy for Oligometastatic Prostate Cancer: A Single-Institutional Prospective Clinical Trial” and is published online at European Urology.