Results from a randomized, controlled trial to compare the use of permanent radioactive implants (brachytherapy) with dose-escalated external beam radiotherapy in patients with prostate cancer show that the men who received brachytherapy were twice as likely to be cancer-free 5 years later. These results were presented at the third ESTRO (European Society for Therapeutic Radiology and Oncology) Forum in Barcelona, Spain.
The ASCENDE-RT1 trial is the first and only existing trial comparing low-dose-rate prostate brachytherapy (LDR-PB) for the curative treatment of prostate cancer with any other method of radiation therapy delivery, stated Professor James Morris, MD, FRCPC, from the Department of Radiation Oncology, Vancouver Cancer Centre, British Columbia Cancer Agency (BCCA), Vancouver, Canada.
The trial enrolled 398 men with cancer that had not spread outside the prostate gland who were judged to be at high risk of treatment failure, based on standard tests for a number of features of the cancer. The patients initially received androgen deprivation therapy (ADT), aimed at reducing levels of the male hormones that stimulate prostate cancer cells to grow. After eight months of ADT, all patients received 46 Gy of external beam radiotherapy to the prostate and regional lymph nodes.
Following this, 198 men received LDR-PB in which tiny radioactive seeds were implanted in the prostate gland while under general or spinal anaesthesia. The other 200 patients were randomized to dose-escalated external beam radiation therapy (DE-EBRT) and received an additional 32 Gy of external beam radiation to achieve a total prostate dose of 78 Gy.
“At 5 years follow up, we saw a large advantage in progression-free survival in the LDR-PB group,” Morris said. “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.”
LDR-PB is an extremely cost-effective treatment, the researchers said, but it does require prolonged training and experience in order to produce consistent results, and this may limit more widespread adoption. An additional problem is that, in the trial, the LDR-PB patients experienced more urinary side effects that those who received DE-EBRT.
In a separate presentation, Dr Sree Rodda, MRCP, FRCR, a clinical research fellow with Morris, told the conference that the incidence of severe late urinary side effects was three times higher in patients who received LDR-PB than in those who had DE-EBRT.
“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.” However, she said, “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.”