Prostate-specific antigen kinetics and biochemical control following stereotactic body radiation therapy, high dose rate brachytherapy, and low dose rate brachytherapy: A multi-institutional analysis of 3502 patients.

BACKGROUND AND PURPOSE: Stereotactic body radiation therapy (SBRT), low dose rate brachytherapy (LDR-BT) and high dose rate brachytherapy (HDR-BT) are ablative-intent radiotherapy options for prostate cancer (PCa). These vary considerably in dose delivery, which may impact post-treatment prostate-specific antigen (PSA) patterns and biochemical control. We compared PSA kinetics between SBRT, HDR-BT, and LDR-BT, and assessed their relationships to biochemical recurrence-free survival (BCRFS). METHODS AND MATERIALS: Retrospective PSA data were analyzed for 3502 men with low-risk (n = 2223; 63.5%), favorable intermediate-risk (n = 869; 24.8%), and unfavorable intermediate-risk (n = 410; 11.7%) PCa treated with SBRT (n = 1716; 49.0%), HDR-BT (n = 512; 14.6%), or LDR-BT (n = 1274; 36.4%) without upfront androgen deprivation therapy at 10 institutions from 1990 to 2017. We compared nadir PSA (nPSA), time to nPSA, achievement of nPSA <0.2 ng/mL and <0.5 ng/mL, rates of nPSA <0.4 ng/mL at 4 years, and BCRFS. RESULTS: Median follow-up was 72 months. Median nPSA and nPSA <0.2 ng/mL were stratified by risk group (interaction p ≤ 0.001). Median nPSA and time to nPSA were 0.2 ng/mL at 44 months after SBRT, 0.1-0.2 ng/mL at 37 months after HDR-BT, and 0.01-0.2 ng/mL at 51 months after LDR-BT (mean log nPSA p ≤ 0.009 for LDR-BT vs. SBRT or HDR-BT for low/favorable intermediate-risk). There were no differences in nPSA <0.4 ng/mL at 4 years (p ≥ 0.51). BCRFS was similar for all three modalities (p ≥ 0.27). Continued PSA decay beyond 4 years was predictive of durable biochemical control. CONCLUSION: LDR-BT led to lower nPSAs with longer continued decay compared to SBRT and HDR-BT, but no differences in BCRFS.

Outcomes of Breast Cancer Patients Treated with Accelerated Partial Breast Irradiation Via Multicatheter Interstitial Brachytherapy: The Pooled Registry of Multicatheter Interstitial Sites (PROMIS) Experience.

PURPOSE: To report outcomes for breast-conserving therapy using adjuvant accelerated partial breast irradiation with interstitial multicatheter brachytherapy by a cooperative group of institutions. METHODS: From 1992 to 2013, a total of 1356 patients were treated with breast-conserving surgery and adjuvant accelerated partial breast irradiation using interstitial multicatheter brachytherapy. A total of 1131 patients had >1 year of data available to assess oncologic and cosmesis outcomes. Median age was 59 years old (range 22-90 years). Histologies treated included 1005 (73 %) invasive ductal carcinoma and 240 (18 %) ductal carcinoma-in situ. T stages were 18 % Tis, 75 % T1, and 8 % ≥T2. Nodal status was 73 % N0 and 6 % N1a. Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 was positive in 83, 70, and 6 %, respectively. Cox multivariate analysis for local control was performed using histology, age, estrogen receptor status, tumor size, grade, margin, and nodal status. RESULTS: The mean (SD) follow-up was 6.9 years (4.3). The 10-year actuarial risk (95 % confidence interval) of an ipsilateral breast tumor recurrence was 7.6 % (5.6-10.1). Other 10-year actuarial risks (95 % confidence interval) were regional failure 2.3 % (1.4-3.7), distant metastasis 3.8 % (2.5-5.7), cause-specific survival 96.3 % (94.2-97.6), overall survival 86.5 (83.0-89.3), and new contralateral cancers 4.6 % (3.0-6.9). On multivariate analysis, high grade (hazard ratio 2.81) and positive margin status (hazard ratio 18.42) were the only two significant variables associated with an increased risk of local recurrence. Physician-reported cosmesis was excellent/good in 84 % (98 of 116) of patients with >5 years of follow-up. CONCLUSIONS: This is the largest report of outcomes with interstitial breast brachytherapy. This treatment resulted in excellent long-term local control and cosmesis outcomes.