Results from the NRG Oncology NRG-RTOG 0232 clinical trial adding external beam radiotherapy (EBRT) to brachytherapy (BT) in men with intermediate-risk prostate cancer indicate that there was no improvement in freedom from progression (FFP) rates for patients.

Late hostile events were significantly increased (> 6 months from treatment start) in genitourinary (GU)/gastrointestinal (GI) and analyzed as grade 2+ and as grade 3+ for patients on the trial who received the mixture of EBRT and BT (COMBO arm) in comparison with patients who received BT alone (BT arm). These results, which were recently published within the Journal of Clinical Oncology, suggest that BT should remain the usual of look after this population.

Many variations and intensifications of each EBRT and brachytherapy have been tested mainly in the upper and lower risk tiers of prostate cancer patients. Intermediate-risk prostate cancer patients represent an unlimited and heterogeneous grouping, which may make it difficult to seek out a particular therapy combination that appropriately treats their disease and the variability of risks which are possible inside this population while avoiding added toxicity.”

Jeff Michalski, Study Lead Writer, Washington University Siteman Cancer Center

NRG-RTOG 0232 randomly assigned588 men with intermediate-risk prostate cancer to either the COMBO or the BT treatment arm and 579 were eligible/analyzed. The COMBO arm consisted of 287 patients versus 292 on the BT arm. The first objective of the trial was to find out whether the mixture of EBRT and BT improved 5-year FFP using the ASTRO definition. Secondary objectives of the trial included FFP using the Phoenix definition, biochemical failure (per ASTRO and Phoenix), disease-specific mortality, local progression, distant metastases, survival, and toxicity.

There was not a big improvement with the COMBO treatment for 5-year FFP rates by each ASTRO and Phoenix definitions. The 5-year FFP-ASTRO rate (95% CI) was 86% (81-90) on the COMBO arm versus 83% (78-87) with on the BT arm. The 5-year FFP-Phoenix rate was 88% (84-92) on the COMBO arm versus 86% (81-90) on the BT arm. There have been no differences between treatment arms for acute GU and GI toxicities; nonetheless, 5-year cumulative incidence of late grade 2 or higher GU/GI toxicities was 43% (37-49) within the COMBO arm and 26% (21-31) within the BT arm (p<0.0001). 5-year cumulative incidence for late grade 3 or higher GU/GI toxicities was 8% (5-12) within the COMBO arm and 4% (2-6) within the BT arm (p=0.006). There have been no grade 5 GU/GI toxicities.

“Although these results favor brachytherapy alone as an ordinary of care, it can be crucial to notice that more research is required to explore local treatment options for chosen intermediate-risk patients that safely improves outcomes,” added Dr. Michalski.

Further evaluation is going on for the quality-of-life secondary endpoint of the NRG-RTOG 0232 study. These data might be reported individually.

Supported by grants UG1CA189867 (NCORP), U10CA180868 (NRG Operations), U24CA180803 (IROC), and U10CA180822 (SDMC) from the National Cancer Institute (NCI).