Stereotactic radiotherapy courses for men with intermediate risk, localised prostate cancer is as effective as standard care, according to the findings of a new trial presented at the recent American Society for Radiation oncology (ASTRO) annual meeting.
The phase 3 PACE B (Prostate Advances in Comparative Evidence) study found that using stereotactic body radiation therapy (SBRT) was non-inferior to standard treatment with moderately fractionated radiation in men with non-metastatic prostate cancer. SBRT had a five-year disease control rate of 96% compared to 95% for conventional radiation.
Researchers from the Royal Marsden Hospital in London, enrolled 874 men with a median age of 69.8 years from 38 centres in Canada and the UK.
Participants were randomly assigned to receive either SBRT (n = 443), which involved the delivery of five fractions over one to two weeks (36.25 Gy total dose), or a standard course of radiation (n = 441) with 39 fractions over 7.5 weeks (78 Gy) or 20 fractions over four weeks (62 Gy). The men were then followed for a median of 73.1 months.
The trial explored whether patients remained free of biochemical clinical failure (BCF), which was defined as an increase in PSA levels, distant metastases or other evidence that the cancer was returning, or death from prostate cancer.
SBRT treatment times have ‘huge implications‘
After five years after treatment with either modality, men treated with SBRT had a BCF-event-free rate of 95.7%, compared to 94.6% for those treated with standard care radiation. This demonstrated that SBRT was non-inferior to CRT (p-value for non-inferiority = 0.007).
Side effects were low in both groups, and not significantly different between treatment arms. At five years post-treatment, 5.5% of patients who received SBRT experienced grade 2 or higher side effects affecting the genital or urinary organs, compared to 3.2% in the conventional group (p = 0.14). Only one person in each arm of the study experienced grade 2 or higher gastrointestinal side effects (p = 0.99).
In discussing these findings, Professor Nicholas van As, consultant clinical oncologist, medical director of The Royal Marsden NHS Foundation Trust and the study lead, said: ‘Standard radiation treatment is already highly effective and is very well tolerated in people with localised prostate cancer.
‘But, for a healthcare system and for patients, to have this treatment delivered just as effectively in five days as opposed to four weeks has huge implications.‘
Stereotactic radiotherapy delivers treatment with high precision from a number of different angles around the body and helps to reduce adverse effects in the surrounding tissue. A study from earlier in 2023 found MRI-guided stereotactic radiotherapy reduced physician-reported toxic GU and gastrointestinal adverse effects than CT-guided stereotactic radiotherapy in men with prostate cancer.
