Purpose To identify an anatomic structure predictive for acute (AUT) and late (LUT) urinary toxicity in patients with prostate cancer treated with low-dose-rate brachytherapy (LDR) with or without external beam radiation therapy (EBRT). Materials and Methods From 7/2002 to 1/2013, 927 patients with prostate cancer (median age, 66) underwent LDR brachytherapy using I-125 (n=753) or Pd-103 (n=174) as definitive treatment (n=478) and as a boost (n=449) followed by supplemental EBRT (median dose, 50.4 Gy). Structures contoured on Day 0 postimplant CT scan included prostate, urethra, bladder, and the bladder neck, defined as 5 mm around the urethra between the catheter balloon and the prostatic urethra. AUT and LUT were assessed using CTCAE v 4. Clinical and dosimetric factors associated with AUT and LUT were analyzed using Cox regression and receiver-operating characteristic analysis to calculate area under the receiver operator curve (ROC) (AUC). Results Grade ≥2 AUT and grade ≥2 LUT occurred in 520 (56%) patients and 154 (20%) patients, respectively. No grade 4 toxicities were observed. Bladder neck D2cc retained significant association with AUT (hazard ratio [HR], 1.03; 95% CI, 1.03–1.04) (P<.0001) and LUT (HR, 1.01; 95% CI, 1.00–1.03 (P=.014) on multivariable analysis. When comparing bladder neck with the standard dosimetric variables using ROC analysis (prostate V100>90%, D90>100%, V150>60%, urethra D20>130%), bladder neck D2cc>50% was shown to have the strongest prognostic power for AUT (AUC, 0.697; P<0.0001) and LUT (AUC, 0.620; P<.001). Conclusions Bladder neck D2cc>50% was the strongest predictor for grade ≥2 AUT and LUT in patients treated with LDR brachytherapy. These data support inclusion of bladder neck constraints into brachytherapy planning to decrease urinary toxicity.

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PurposeTo compare health-related quality of life (HRQOL) of high-dose-rate brachytherapy (HDRB) versus low dose-rate brachytherapy (LDRB) for localized prostate cancer in a multi-institutional phase 2 randomized trial.Methods and MaterialsMen with favorable-risk prostate cancer were randomized between monotherapy brachytherapy with either Iodine-125 LDRB to 144 Gy or single-fraction Iridium-192 HDRB to 19 Gy. HRQOL and urinary toxicity were recorded at baseline and at 1, 3, 6, and 12 months using the Expanded Prostate Cancer Index Composite (EPIC)-26 scoring and the International Prostate Symptom Score (IPSS). Independent samples t test and mixed effects modeling were performed for continuous variables. Time to IPSS resolution, defined as return to its baseline score ±5 points, was calculated using Kaplan-Meier estimator curves with the log-rank test. A multiple-comparison adjusted P value of ≤.05 was considered significant.ResultsLDRB and HDRB were performed in 15 and 16 patients, respectively, for a total of 31 patients. At 3 months, patients treated with LDRB had a higher IPSS score (mean, 15.5 vs 6.0, respectively; P = .003) and lower EPIC urinary irritative score (mean, 69.2 vs 85.3, respectively; P = .037) compared with those who received HDRB. On repeated measures at 1, 3, 6, and 12 months, the IPSS (P = .003) and EPIC urinary irritative scores (P = .019) were significantly better in the HDR arm, translating into a lower urinary toxicity profile. There were no significant differences in the EPIC urinary incontinence, sexual, or bowel habit scores between the 2 groups at any measured time point. Time to IPSS resolution was significantly shorter in the HDRB group (mean, 2.0 months) compared with the LDRB group (mean, 6.0 months; P = .028).ConclusionsHDRB monotherapy is a promising modality associated with a lower urinary toxicity profile and higher HRQOL in the first 12 months compared with LDRB.

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