PP06  Presentation Time: 10:05 AM: Comparison of Perioperative & Subacute Postoperative Complications between LDR & HDR Brachytherapy for Prostate Cancer

Purpose The efficacy of low dose rate (LDR) and high dose rate (HDR) brachytherapy for prostate cancer have been well established. Fewer studies directly compare short-term perioperative complications between these modalities, and these often have small sample sizes and heterogeneous settings including brachytherapy boost after external beam radiotherapy (EBRT). The purpose of this study is to investigate the perioperative and subacute postoperative complications in patients undergoing exclusively LDR or HDR monotherapy at a single institution with a high volume brachytherapy program. We hypothesize a favorable acute and subacute toxicity profile in patients treated with HDR monotherapy compared to LDR. Materials and Methods Patients age >18 with biopsy proven prostate cancer and treated with HDR or LDR implants alone, between 1998-2021 were identified from a prospectively collected, IRB approved institutional database. Toxicities and grades were determined as per CTCAE v3, and those within 4 months of treatment were defined as perioperative or subacute postoperative complications associated with brachytherapy. We used Fisher's exact tests and Wilcoxon rank sum tests to determine the association between the complication groups and patient/treatment factors. Results There were a total of 759 patients included for analysis, 446 received LDR using 125iodine (125I) or 103palladium (103Pd), and 313 received HDR using 192iridium (192Ir). HDR patients were slightly older than LDR patients (median age 67 vs 65, p=0.001) and had higher risk features: HDR patients had higher Gleason scores (75.7% with GS 7+ versus 2.4% of LDR patients) and higher initial PSA values (16% with 10+ ng/mL versus 2.7% of LDR patients). Reported acute and subacute toxicity were mild with the most common toxicity among all patients being grade 1 GU frequency and nocturia, each at ∼50%. GI toxicity was rare, with highest incidence being grade 1 frequency in 12.6% of patients. Grade 3 toxicities were exceedingly rare, with only 1 grade 3 GI toxicity, and 18 (2.4%) cases of grade 3 urinary obstructive symptoms. There is a significant difference in toxicity profile between LDR and HDR. Patients receiving HDR had significantly less grade 2+ urinary symptoms, including dysuria (2.6% vs 9.0%, p<0.001), frequency (4.8% vs 9.9%, p=0.01), hematuria (1.0% vs 6.1%, p<0.001), nocturia (3.8% vs 9.9%, p=0.002), and urinary obstructive symptoms (8.9% vs 14.1%, p=0.03). Infection rates were low, with 12 (1.6%) patients total experiencing GU related infections requiring antibiotics: 8 (1.8%) from the LDR group and 4 (1.3%) from the HDR group. Lastly, there is a clear pattern of change in institutional practice, evolving from LDR based to now an HDR based program. Conclusions In this large single institution analysis, HDR monotherapy is associated with significantly less perioperative and subacute post-operative complications when compared to LDR monotherapy. Toxicity rates were low in both groups, although GU toxicities were significantly more common than GI in both modalities. These data provide evidence supporting a favorable toxicity profile of HDR monotherapy compared to LDR monotherapy for prostate cancer. Interestingly, data from this high volume brachytherapy program also revealed a greater proportion of HDR patients having more advanced disease prior to therapy, and the evolution of an institutional trend in treatment from only performing LDR to HDR only over time. The efficacy of low dose rate (LDR) and high dose rate (HDR) brachytherapy for prostate cancer have been well established. Fewer studies directly compare short-term perioperative complications between these modalities, and these often have small sample sizes and heterogeneous settings including brachytherapy boost after external beam radiotherapy (EBRT). The purpose of this study is to investigate the perioperative and subacute postoperative complications in patients undergoing exclusively LDR or HDR monotherapy at a single institution with a high volume brachytherapy program. We hypothesize a favorable acute and subacute toxicity profile in patients treated with HDR monotherapy compared to LDR. Patients age >18 with biopsy proven prostate cancer and treated with HDR or LDR implants alone, between 1998-2021 were identified from a prospectively collected, IRB approved institutional database. Toxicities and grades were determined as per CTCAE v3, and those within 4 months of treatment were defined as perioperative or subacute postoperative complications associated with brachytherapy. We used Fisher's exact tests and Wilcoxon rank sum tests to determine the association between the complication groups and patient/treatment factors. There were a total of 759 patients included for analysis, 446 received LDR using 125iodine (125I) or 103palladium (103Pd), and 313 received HDR using 192iridium (192Ir). HDR patients were slightly older than LDR patients (median age 67 vs 65, p=0.001) and had higher risk features: HDR patients had higher Gleason scores (75.7% with GS 7+ versus 2.4% of LDR patients) and higher initial PSA values (16% with 10+ ng/mL versus 2.7% of LDR patients). Reported acute and subacute toxicity were mild with the most common toxicity among all patients being grade 1 GU frequency and nocturia, each at ∼50%. GI toxicity was rare, with highest incidence being grade 1 frequency in 12.6% of patients. Grade 3 toxicities were exceedingly rare, with only 1 grade 3 GI toxicity, and 18 (2.4%) cases of grade 3 urinary obstructive symptoms. There is a significant difference in toxicity profile between LDR and HDR. Patients receiving HDR had significantly less grade 2+ urinary symptoms, including dysuria (2.6% vs 9.0%, p<0.001), frequency (4.8% vs 9.9%, p=0.01), hematuria (1.0% vs 6.1%, p<0.001), nocturia (3.8% vs 9.9%, p=0.002), and urinary obstructive symptoms (8.9% vs 14.1%, p=0.03). Infection rates were low, with 12 (1.6%) patients total experiencing GU related infections requiring antibiotics: 8 (1.8%) from the LDR group and 4 (1.3%) from the HDR group. Lastly, there is a clear pattern of change in institutional practice, evolving from LDR based to now an HDR based program. In this large single institution analysis, HDR monotherapy is associated with significantly less perioperative and subacute post-operative complications when compared to LDR monotherapy. Toxicity rates were low in both groups, although GU toxicities were significantly more common than GI in both modalities. These data provide evidence supporting a favorable toxicity profile of HDR monotherapy compared to LDR monotherapy for prostate cancer. Interestingly, data from this high volume brachytherapy program also revealed a greater proportion of HDR patients having more advanced disease prior to therapy, and the evolution of an institutional trend in treatment from only performing LDR to HDR only over time.