Addition of a brachytherapy boost to external beam radiation therapy (EBRT) reduces prostate cancer (PCa) recurrence at the expense of genitourinary (GU) toxicity. Whether brachytherapy boost technique, specifically low-dose-rate (LDR-BT) versus high-dose-rate (HDR-BT), impacts treatment-related toxicity is unclear.
Between 2012-2018, 106 men with intermediate/high risk PCa underwent EBRT (37.5-45 Gy in 1.8-2.5 Gy/fraction) plus brachytherapy boost, either with LDR-BT (110 Gy I-125 or 100 Gy Pd-103; n = 51) or HDR-BT (15 Gy x1 Ir-192; n = 55). Patient-reported outcomes (PRO) were assessed by International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index Composite (EPIC-CP) surveys at 3-6-month intervals for up to three years following treatment, with higher scores indicating more severe toxicity. Provider-reported GU and gastrointestinal (GI) toxicity was graded per CTCAE v5.0 at each follow-up. Linear mixed models comparing PROs between LDR-BT versus HDR-BT were fitted. Stepwise multivariable analysis (MVA) was performed to account for age, gland size, androgen deprivation therapy use, and alpha-blocker medication use. Incidence rates of grade 2+ GU/GI toxicity was compared using Fisher's exact test.
Use of LDR-BT was associated with greater change in IPSS (p=0.003) and EPIC-CP urinary irritative score (p = 0.002) compared with HDR-BT, but effect size diminished over time (LDR-BT versus HDR-BT: baseline to 6-/24-month mean IPSS change, +6.4/+1.4 versus +2.7/-3.0, respectively; mean EPIC-CP irritative/obstructive change, +2.5/+0.1 versus +0.9/+0.1, respectively). Results remained significant on MVA. Post-treatment grade 2+ GU toxicity was significantly higher in the LDR-BT group (67.5% versus 42.9% for LDR-BT and HDR-BT, respectively; p <0.001). There were no differences between groups in incontinence, bowel function, and erectile function, or grade 2+ GI toxicity.
Compared with LDR-BT, HDR-BT was associated with lower acute patient- and provider-reported GU toxicity.
Brachytherapy. 2021 Aug 18 [Epub ahead of print]
Vishal R Dhere, Benjamin W Fischer-Valuck, Subir Goyal, Yuan Liu, Tiffany M Morgan, Elizabeth Ghavidel, Drew M Moghanaki, Bruce W Hershatter, Pretesh R Patel, Ashesh B Jani, Karen D Godette, Peter J Rossi, Sagar A Patel
Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta GA., Department of Biostatistics and Bioinformatics, Emory University, Atlanta GA., New Hanover Regional Medical Center, Wilmington NC., Calaway Young Cancer Center, Valley View Hospital, Glenwood Springs CO., Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta GA. Electronic address: .