Androgen deprivation (ADT) was used in 74%, with a 12-month duration for the majority but some IR patients prescribed 0-6 months. Quality of Life (QoL) was prospectively collected using the International Prostate Symptom Score (IPSS), International Index of Erectile Function (IIEF), and the Expanded Prostate Cancer Index Composite (EPIC) at baseline, 1, 3, and 6 months after the start of radiation, then every 6 months until 3 years and every 12 months until 5 years. The study was completed at one regional Cancer Center in the province of British Columbia, Canada, where LDR boost has been commonly used for these patients for many years. In 2010 an HDR prostate brachytherapy program was introduced, and it was observed that HDR patients seemed to recover much more quickly after completing their combined EBRT and brachytherapy than we were accustomed to seeing after an LDR boost. Thus, this randomized trial was initiated to test our clinical suspicion.
Shortly after opening to accrual in 2014, the trial increased in importance. The results of the Ascende-RT trial were published in 2017 demonstrating remarkable efficacy of the LDR boost compared to EBRT alone (78 Gy) in a similar cohort of patients with unfavorable prostate cancer, all of whom also received 12 months of ADT.2-3 Biochemical “no evidence of disease” (BNED) at 9 years was 83% compared to 62% for 78Gy (p=0.004). Unfortunately, this efficacy came at a price, with unacceptable cumulative grade 3 GU toxicity reported at 18.3%. Although much of this toxicity was managed and resolved, such that the 5-year prevalence of grade 3 GU toxicity was down to 8.8%, this was still much higher than that experienced by many brachytherapy practitioners. Our QoL trial, designed with the hope of showing that HDR boost patients had an easier time with treatment than LDR boost patients, now had a second mission. It would provide a second look at late toxicity using patient-reported outcomes prospectively collected on this cohort of LDR boost patients who followed Ascende-RT.
Our Findings
HDR boost patients do recover more quickly than LDR as determined by both the IPSS and the EPIC urinary score (6 months for recovery to baseline for HDR vs. 18 months for LDR) but contrary to the Ascende RT results, there was no surplus of late GU toxicity observed in these LDR boost patients. The EPIC urinary score was the same for both types of brachytherapy from 18 months to 60 months. In terms of CTCAE V5 toxicity, there was only 1 late grade 3 event in each arm.
For the EPIC bowel score, the low point for both cohorts was 12 months. This may seem late but it must be recalled that both cohorts received 46 Gy of EBRT. The HDR patients then recovered to close to baseline, with the difference being less than the MCID (minimal clinically important difference), while LDR patients maintained a difference from baseline that was slightly greater than the MCID out to 5 years. There was one grade 3 CTCAE V5 late GI event in the LDR arm but none in the HDR arm.
Our conclusions are that if both types of brachytherapy boost are available, HDR patients do tend to recover more quickly, but an LDR boost is also safe with no difference in long term urinary QOL out to 5 years between the 2 treatments.
Efficacy results comparing the 2 types of boost will be presented this year and may be the deciding factor when selecting one type of brachy over the other.
Written by: Juanita Crook, MD, FRCPC, Professor of Radiation Oncology, University of British Columbia, BCCA Center for the Southern Interior, Kelowna, British Columbia, Canada
References:
- Crook J, Moideen N, Arbour G, et al. A Randomized Trial Comparing Quality of Life After LDR or HDR Prostate Brachytherapy Boost with Pelvic External Beam Radiation Therapy. Int J Radiat Oncol Biol Phys. 2024. doi:10.1016/j.ijrobp.2024.02.064
- Morris WJ, Tyldesley S, Rodda S, et al. Androgen Suppression Combined with Elective Nodal and Dose Escalated Radiation Therapy (the ASCENDE-RT Trial): An Analysis of Survival Endpoints for a Randomized Trial Comparing a Low-Dose-Rate Brachytherapy Boost to a Dose-Escalated External Beam Boost for High- and Intermediate-risk Prostate Cancer. Int J Radiat Oncol Biol Phys. 2017;98(2):275-285. doi:S0360-3016(16)33484-8 [pii]
- Rodda S, Morris WJ, Hamm J, Duncan G. ASCENDE-RT: An Analysis of Health-Related Quality of Life for a Randomized Trial Comparing Low-Dose-Rate Brachytherapy Boost With Dose-Escalated External Beam Boost for High- and Intermediate-Risk Prostate Cancer. Int J Radiat Oncol Biol Phys. 2017;98(3):581-589. doi:S0360-3016(17)30405-4 [pii]