TOPLINE:

A pooled analysis of five prospective trials showed that stereotactic body radiotherapy (SBRT) was associated with a lower risk for biochemical failure over 10 years vs high-dose rate brachytherapy (HDR-BT), as well as fewer acute genitourinary side effects.

METHODOLOGY:

• SBRT and HDR-BT monotherapy are guideline-recommended treatment options for men with intermediate-risk prostate cancer. The modalities have similarities, including ablative techniques with high doses per fraction. However, prospective data comparing the two are lacking.
• To address this gap, researchers conducted a post hoc pooled analysis of individual patient data from five prospective trials involving 247 men with intermediate-risk prostate cancer who underwent SBRT (n = 180; mean age, 69.5 years) or HDR-BT (n = 67; mean age, 66.0 years).
• SBRT was delivered as either 40 Gy in five fractions to the prostate with a 5-mm planning target volume margin or 26 Gy in two fractions to the prostate with seminal vesicle expansion and a 2- to 3-mm planning target volume margin. HDR-BT was delivered as two fractions of 13.5 Gy each, administered 1-2 weeks apart, using intraoperative transrectal ultrasonography-based planning under general anesthesia.
• The primary outcome was biochemical failure (prostate-specific antigen [PSA] nadir plus 2.0 ng/mL). Secondary outcomes included patient-reported quality of life and clinician-reported adverse events. Median follow-up was 9.5 years.

TAKEAWAY:

• The cumulative incidence of biochemical failure was 7.8% vs 3.0% with HDR-BT vs SBRT at 5 years and 38.0% vs 10.4% with HDR-BT vs SBRT at 10 years (P < .001 for both). Overall, 19 patients (28.4%) vs 13 patients (7.2%) in the HDR-BT cohort vs the SBRT cohort had biochemical failure.
• In a multivariable analysis, HDR-BT vs SBRT was associated with a higher risk for biochemical failure (hazard ratio [HR], 5.26; P < .001), as was PSA level ≥ 10 ng/mL vs < 10 ng/mL (HR, 3.86; P < .001). Regarding PSA outcomes, the median PSA nadir was not significantly different between HDR-BT and SBRT (P = .14), but the 4-year PSA response rate was lower after HDR-BT (56.7% vs 68.3%; P = .02).
• Regarding adverse events, HDR-BT was associated with a higher incidence of acute genitourinary adverse events of grade 2 or higher than SBRT (74.6% vs 51.7%; P = .007). But there were no significant differences in the incidence of acute or late gastrointestinal or sexual adverse events.
• No significant differences were observed between the HDR-BT and SBRT cohorts in long-term patient-reported quality of life or in the cumulative incidence of distant metastases, cancer-specific survival, or overall survival.

IN PRACTICE:

“This study’s long-term outcomes, including that SBRT was associated with decreased biochemical failure, may inform discussions regarding radiation modality selection for intermediate-risk prostate cancer,” according to the authors of the study. The findings, they add, also highlight a potential need for ongoing follow-up past 5 years for men with intermediate-risk disease, particularly those undergoing HDR-BT.

SOURCE:

The study, led by Cristian Udovicich, MBBS, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, was published online in JAMA Network Open.

LIMITATIONS:

Dose fractionation in the SBRT cohort was heterogeneous, potentially affecting outcomes. There was an imbalance in the availability of data on adverse events, and patient-reported quality of life in the short term could not be assessed. Additionally, the findings may not be generalizable to HDR-BT regimens with more than two fractions.

DISCLOSURES:

The authors did not disclose any funding information. Several authors reported receiving personal fees from various sources including TerSera Therapeutics LLC, AstraZeneca, Bayer, Eisai, Pfizer, and others. One author reported holding a patent for an endorectal immobilization device issued to MOLLI Surgical. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.