Low-dose-rate (LDR) brachytherapy appears to provide excellent outcomes in men treated for localized organ-confined prostate cancer (PCa), according to researchers at Mayo Clinic in Rochester, Minnesota.
In a study of 974 men who received I-125 LDR brachytherapy for low- and intermediate-risk PCa, a team led by radiation oncologist Brian Davis, MD, found that the 10-year rate of freedom from biochemical failure was 88% overall, but was significantly worse for men with intermediate- than low-risk disease (76% vs 92%). The local recurrence rate was 2.1% at 10 years.
The men had a mean follow-up period of 72 months. The investigators defined biochemical failure by Phoenix criteria (PSA nadir + 2 ng/mL).
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On multivariable analysis, primary Gleason 4+3 disease, higher pretreatment PSA, and absence of androgen deprivation therapy (ADT) were the only factors associated with biochemical failure. Gleason 4+3 disease increased the likelihood of distant metastasis and PCa-specific death, Dr Davis’ team reported online ahead of print in Brachytherapy.
Michael R. Folkert, MD, PhD, Assistant Professor of Radiation Oncology at the University of Texas Southwestern Medical Center in Dallas, who was not involved in the new study, called the work by Dr Davis and his colleaguess a high-quality investigation with a carefully followed patient population.
“This paper reaffirms what most radiation oncologists specializing in prostate brachytherapy already know,” Dr Folkert told Renal & Urology News. “For low risk and favorable intermediate-risk prostate cancer, prostate brachytherapy represents an elegant and highly effective treatment in expert hands. Prostate brachytherapy is a convenient and proven approach for managing prostate cancer with a single visit to the operating room for seed placement.”
For patients with more aggressive disease, such as those with Gleason 4+3 disease, a PSA level greater than 10 ng/mL, or disease involving half or more of the prostate, brachytherapy alone may be insufficient, as cancer control rates were only 74% at 5 years in the current study. “This still compares favorably with surgery, where 5-year control in the unfavorable intermediate-risk population would be expected to be between 32% and 68%,” Dr Folkert said.
Judd W. Moul, MD, Professor of Surgery and the Director of the Duke Prostate Center at Duke University Medical Center in Durham, North Carolina, said these study findings are highly relevant because the researchers looked at a very large series with a relatively long-term follow-up. “The authors use the Phoenix criteria, which is a full 2-point rise in the post-treatment PSA level from the post-treatment nadir PSA,” Dr Moul said. “While this is proper and meets guideline criteria for biochemical recurrence after radiation, it is also somewhat controversial as compared to the recurrence definition of 0.2 or higher for surgically treated men. In other words, some experts, particularly experts who favor surgery, feel the Phoenix definition of recurrence of allowing the PSA as high as 2.0 or even greater (if the nadir was detectable) artificially makes radiation ‘look better’ than surgery with regard to biochemical control.”
However, he said he generally tells his patients that all treatments for low- and intermediate-risk disease offer similar outcomes at 7 to 10 years, and this study confirms that. Despite the findings from Dr Davis’ team, Dr Moul said he believes surgery is generally preferable for disease control for men who have a greater than 20-year life expectancy. “However, I really would love to see these data reexamined after a median of 15 years of follow-up to help answer the age-old question of what is better for young men with very long life-expectancy,” he said.
Urologic oncologist Soroush Rais-Bahrami, MD, Associate Professor of Urology and Radiology at the University of Alabama at Birmingham, said the oncologic outcomes with LDR prostate brachytherapy as measured in this current study are less optimal in patients with Grade Group 3 or greater tumors. These men may be better candidates for other forms of treatment, including radical prostatectomy or external beam radiation therapy with concurrent ADT. Also, “as the use of active surveillance increases for men diagnosed with low-grade and selected favorable intermediate-risk Grade Group 2 cancers, the oncologic efficacy of LDR brachytherapy as a single-modality treatment should be balanced with its risks and side effect profile,” Dr Rais-Bahrami said.
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References
Routman DM, Funk RK, Stish BJ, et al. Permanent prostate brachytherapy monotherapy with I-125 for low- and intermediate-risk prostate cancer: Outcomes in 974 patients. Brachytherapy. 2018; published online ahead of print.
