Recent results of a controlled, randomized clinical trial comparing the use of permanent radioactive implants (brachytherapy) with external beam, dose-escalated radiotherapy in individuals suffering with prostate cancer revealed that patients who received brachytherapy were 2 times more likely to be cancer-free 5 years after treatment. The results were presented by James Morris, professor at the Department of Radiation Oncology, Vancouver Cancer Centre, British Columbia Cancer Agency (BCCA), Vancouver, Canada, during the 3rd ESTRO Forum in Barcelona, Spain.
The ASCENDE-RT1 trial is the first and only study comparing low-dose-rate prostate brachytherapy (LDR-PB) to address treatment of prostate cancer with any kind of radiation therapy delivery method.
A total of 398 men diagnosed with cancer not yet spread to other zones outside the prostate gland were enrolled in the trial. These men, based on several features of the cancer, were at high risk of treatment failure. At first, individuals received androgen deprivation therapy (ADT), aimed to reduce levels of male hormones that stimulate prostate cancer cells to grow. After 8 months of receiving ADT, men were treated with 46 Gy2 of external beam radiotherapy targeted at the prostate and regional lymph nodes.
After this approach, 198 men received LDR-PB, and very small radioactive seeds were implanted in their prostate glands. The remaining 200 patients were randomized to dose-escalated external beam radiation therapy (DE-EBRT) and were addressed with an additional 32 Gy of external beam radiation to achieve a total prostate dose of 78 Gy.
“At five years follow up, we saw a large advantage in progression-free survival in the LDR-PB group. Although, to date, overall survival and prostate cancer-specific survival do not appear to differ between the two groups, existing trends favor LDR-PB and an overall survival advantage is likely to emerge with longer follow-up,” said Prof Morris.
LDR-PB is an effective and affordable treatment but requires long experience and training to conquer consistent results. Further, some side effects were experienced: LDR-PB individuals experienced more urinary side effects than DE-EBRT (three times more). “Many of these severe adverse effects were temporary and reversible, or could be ameliorated by procedures. Moreover, more than 80% of patients in the LDR-PB arm had few or no long term urinary side effects. The long-term prevalence of severe urinary toxicity in the LDR-PB patients was 8% compared to just 2% for the DE-EBRT patients. An important challenge for the future will be the reduction of these adverse effects while maintaining the advantages of LDR-PB,” Dr. Morris explained.
“The ideal next step would be to undertake randomized comparisons of LDR-PB boost against its principal alternatives — temporary high-dose-rate brachytherapy implants (HDR-PB)3, stereotactic body radiation therapy using extreme hypofractionation4, and combined surgery and post-operative radiation therapy. In the meantime, ASCENDE-RT has made an important contribution to the search for a more effective curative treatment for prostate cancer,” professor Morris added.
“This study illustrates very nicely how the best results can be obtained by combining various treatment options instead of trying to get the most out of one single modality. Brachytherapy is an extremely efficient and safe radiation oncology modality, and this trial shows that it can have a wider field of applicability than simply in very localized and low risk tumors when combined with other techniques — in this case, androgen deprivation therapy and external bean radiation therapy,” commented Philip Poortmans, ESTRO’s president.