Low-dose-rate (LDR) brachytherapy with or without androgen deprivation therapy may be the optimal treatment option for men with T1c to T3a prostate cancer (PCa), according to a new retrospective study published in Oncology Letters.

Compared with radical prostatectomy (RP), LDR appears to achieve equivalent biochemical relapse-free survival (bRFS) and clinical relapse-free survival time (cRFS) rates.

Investigators compared bRFS and cRFS between 218 patients who underwent LDR brachytherapy with 125I seeds and 211 patients who underwent RP. All patients received treatment from January 2010 and June 2015; and the median follow-up time was 46.6 months.

“There has been a controversy over the merits and demerits of these 2 treatments, said corresponding author Weigang Yan, MD, of Peking Union Medical College Hospital in Beijing, China.

At 1, 2, and 5 years post-treatment, the bRFS rate in the brachytherapy group was 89.4%, 87.2%, and 79.9%, respectively. In the RP arm, the rates were 91.0%, 82.8%, and 72.2%, respectively. At those same time points, the cRFS rates in the brachytherapy group were 99.1%, 97.7%, and 94.9%, respectively. For the RP patients, the rates were 99.0%, 96.2%, and 94.5%, respectively.

On multivariate analysis, T stage T2b or higher independently predicted biochemical failure.

The risk of biochemical failure was significantly higher for the RP group compared with the brachytherapy arm among patients with a Gleason score of 3+4 or less or an initial PSA level of 10 ng/mL or less. Therefore, the investigators believe LDR brachytherapy is a better option for these patients, Dr Yan told Renal & Urology News.

The researchers noted that it is difficult to directly compare both treatment modalities head-to-head because of methodologic biases arising from the differences in baseline characteristics. In general, men who are offered LDR brachytherapy tend to be older and have higher comorbidity scores and more aggressive cancer-associated features, according to the authors. In the current study, the median age of the men was 71 years overall, but it was 74 years in the brachytherapy group compared with 66 years for the RP group.

All men in the RP group underwent laparoscopic procedures. The mean radiation dose for men in the brachytherapy was 144 Gy. In addition, 89% of brachytherapy patients received neoadjuvant or adjuvant andogen deprivation therapy (ADT) compared with 24.6% of the patients in the RP group.

During follow-up, only 3 patients in the RP group and 4 in the brachytherapy group died. As a result of these low mortality rates, the authors noted, it was not possible to compare cancer-specific and other-cause mortality between the groups. “Although the study’s median follow-up time of 46.6 months was sufficient to capture a considerable number of systemic failure events, it may have remained too brief to achieve mortality results,” the authors wrote.

Other limitations included differences in baseline characteristics and the use of ADT between the groups, they noted.

Kosj Yamoah, MD, PhD, Section Chief of Genitourinary Radiation Oncology, and Director of Radiation Oncology Disparities Research at the Moffitt Cancer Center in Tampa, Florida, said the study is important because it confirms similar findings but in a more modern cohort. “Given that this is a more modern cohort of patients spanning 2010 to 2015, this study represents a more current staging era and is less likely to be subject to issues with stage migration when analyzing older cohorts,” Dr Yamoah said. He added that the follow-up period of less than 4 years is relatively short for localized PCa, so clinicians must interpret the findings cautiously.

Leonard J. Appleman, MD, PhD, an oncologist at the University of Pittsburgh Medical Center’s Hillman Cancer Center, said the new study adds to a considerable body of retrospective investigations of the use of brachytherapy for localized PCa.  The study was well-conducted and the paper was well-written. “For low-risk disease,” Dr Appleman said, “it doesn’t matter very much which local therapy you pursue in terms of long-term survival. For the higher-risk cases, I think there are less data for brachytherapy as a single modality.”

Soroush Rais-Bahrami, MD, Associate Professor of Urology and Radiology and the Co-Director at the Program for Personalized Prostate Cancer Care at the University of Alabama at Birmingham, said the new findings are limited because of the use of ADT. “The vast majority of patients who got brachytherapy got some sort of androgen deprivation,” Dr Rais-Bahrami said, “but in the radical prostatectomy patients, the vast majority got no form of hormone deprivation therapy. So, we have to be careful how we look at these data,” said Dr. Rais-Bahrami. “The 2 groups were not well matched in this study based on the ADT given.” 

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Bobby Liaw, MD, Clinical Director of Genitourinary Oncology for the Mount Sinai Health System in New York, noted that, because the study was conducted at a single institution, the applicability to the broader PCa patient population is questionable. “One center might have a particular way of doing things,” Dr. Liaw said. “They [the investigators] attempted to make this a randomized study, but the patients picked which arm they went into. It would be nice to have purely randomized study, but because of patient bias it has not been possible.”

Another limitation as the absence of information about doctors arrived at the decision to place patients on hormone therapy, he said. “Brachytherapy is not offered everywhere, and it requires specialized training,” Dr. Liaw said. “They needed another arm, looking at external beam radiation therapy.”

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Reference

Zhou Z, Yan W, Zhou Y, et al.125I low-dose-rate prostate brachytherapy and radical prostatectomy in patients with prostate cancer. Oncol Lett. 2019;18:72-80.

doi: 10.3892/ol.2019.10279