Permanent Radiotherapy Implants Reported to Decrease Prostate Cancer Recurrence Risk at 5 Years

Permanent Radiotherapy Implants Reported to Decrease Prostate Cancer Recurrence Risk at 5 Years

Dr. James Morris from the British Columbia Cancer Agency (BCCA) in Canada recently presented at the 3rd ESTRO Forum in Barcelona, Spain the results of the ASCENDE-RT trial (Androgen Suppression Combined with Elective Nodal and Dose Escanodal and Dose Escalated Radiation Therapy) assessing prostate cancer treatment via low-dose-rate prostate brachytherapy (LDR-PB), characterized by the use of permanent radioactive implants, in comparison to other radiation therapy delivery methods. The presentation was entitled “LDR Brachytherapy is Superior to 78 Gy of EBRT for Unfavourable Risk Prostate Cancer: The Results of a Randomized Trial.”

In total, 398 prostate cancer patients were enrolled in the ASCENDE-RT randomized controlled trial. All patients had cancer only in the prostate gland with no spread to other organs or tissues, and were considered to be at high risk for treatment failure. Initially, patients were given androgen deprivation therapy (ADT) in order to reduce male hormone levels known to induce the growth of prostate cancer cells. Eight months after ADT, patients received 46 Gray (measure of radiation dose) of external beam radiotherapy in their prostate and regional lymph nodes. After this procedure, 198 patients were submitted to LDR-PB, where tiny radioactive seeds were implanted in the prostate gland, while the remaining 200 patients were given dose-escalated external beam radiation therapy (DE-EBRT) with an extra 32 Gray to reach a total dose of 78 Gray.

Researchers found that patients who received brachytherapy were twice as likely to be cancer-free after five years in comparison to patients under EBRT. “At five years follow up, we saw a large advantage in progression-free survival in the LDR-PB group,” said Dr. Morris in a news release. “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 has, however, some inherent issues that may compromise a more widespread adoption, namely the fact that it is an extremely cost-effective treatment, and it requires prolonged training and experience to generate consistent results. Patients under LDR-PB treatment were also found to experience severe urinary side effects with a three times higher frequency in comparison to patients under 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,” said Clinical Research Fellow at Dr. Morris group, Dr. Sree Rodda. However, “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.”

LDR-PB boost has now been adopted at BCCA’s five cancer centers as the standard of care for men with unfavorable risk localized prostate cancer. “The ideal next step (…) would be to undertake randomized comparisons of LDR-PB boost against its principal alternatives” said Dr. Morris. “In the meantime, ASCENDE-RT has made an important contribution to the search for a more effective curative treatment for prostate cancer.”

“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 beam radiation therapy,” concluded the President of ESTRO, Dr. Philip Poortmans.

Prostate cancer is the second most common cancer in men, with almost one million new cases diagnosed every year worldwide. In the United States, it is estimated that 221,000 new cases will be diagnosed in 2015, resulting in approximately 27,500 deaths.

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