Correlations of post-implant regional dosimetric parameters at 24 hours and one month, with clinical results of low-dose-rate brachytherapy for localized prostate cancer

Evaluation of transrectal ultrasound-based dosimetry for brachytherapy of prostate cancer: a single-center experience

Purpose

To explore the possibility of intraoperative transrectal ultrasound (TRUS)-based dose verification in transperineal brachytherapy (BT) with iodine-125 (¹²⁵I) seeds for prostate cancer.

Material and methods

Fifteen patients with prostate cancer were treated using BT with ¹²⁵I seeds. Post-implant TRUS and computed tomography (CT) images were imported into treatment planning system (TPS) for dosimetry. Dosimetry parameters, including minimum dose received by 90% of the volume (D₉₀), percentage of the volume receiving 100% of prescribed dose (V₁₀₀), and percentage of the volume receiving 200% of prescribed dose (V₂₀₀) were calculated based on TRUS and CT images, separately. The D₉₀ value of TRUS-based dosimetry was transformed to its expected value. Comparisons of the dosimetric parameters between post-operative verification and preoperative plans were made by paired t-test. One-way ANOVA model was used to assess the differences in preoperative plans. Agreements were evaluated between the preoperative planning and post-operative actual dose parameters using Bland-Altman analysis.

Results

In total, 825 of ¹²⁵I seeds were implanted successfully in 15 patients. In TRUS-based dosimetry, 674 seeds (81%) were identified clearly in TRUS-based images, and the expected value of D₉₀ parameter showed no significant differences compared with the preoperative planning and CT post-operation results (p > 0.05). In CT-based dosimetry, 810 seeds (98%) were identified clearly in CT-based images, and there was good consistency of D₉₀, V₁₀₀, and V₂₀₀ values (p > 0.05). Post-implant CT-based dosimetry indicated that ¹²⁵I seed implantation had fulfilled the expected plan.

Conclusions

Intraoperative TRUS can be used for dosimetric verification of BT for prostate cancer.

Comparison of post-implant dosimetrics between intraoperatively built custom-linked seeds and loose seeds by sector analysis at 24 hours and 1 month for localized prostate cancer

Purpose

To compare post-implant dosimetrics between intraoperatively built custom-linked (IBCL) seeds and loose seeds (LS) at 24 hours and 1 month by sector analysis, and to evaluate the effect of IBCL seeds with regard to change in dosimetric parameters, in patients with prostate cancer treated with brachytherapy.

Material and methods

Consecutive patients treated for localized prostate cancer who received definitive brachytherapy between March 2013 and October 2017 were retrospectively analyzed. Prostate V₁₀₀ (PV₁₀₀), prostate D₉₀ (PD₉₀), prostate V₁₅₀ (PV₁₅₀), urethral D₃₀ (UD₃₀), urethral V₁₅₀ (UV₁₅₀), and rectal V₁₀₀ (RV₁₀₀) were assessed.

Results

Thirty-two patients were treated with LS and 32 patients were treated with IBCL seeds. The median follow-up time was 49.9 months in the LS group and 27.1 months in the IBCL group. PV₁₅₀, UV₁₅₀, and UD₃₀ at 24 hours and UD₃₀ at 1 month showed significant difference (F-test), and standard deviation (SD) tended to be lower in the IBCL group. Analysis of change in the variables revealed significance for ΔPV₁₀₀ and ΔPD₉₀ (F-test, p = 0.014 and < 0.001, respectively), and ΔPV₁₅₀ and ΔUD₃₀ showed marginal significance (p = 0.084 and 0.097, respectively). PV₁₅₀, UV₁₅₀, and UD₃₀ at 24 hours and 1 month were significantly lower in the IBCL group, and there was no significant difference in PV₁₀₀, PD₉₀, and RV₁₀₀ compared with the LS group (t-test). The homogeneity index (HI) was significantly higher in the IBCL group (p < 0.001).

Conclusions

In this retrospective single institutional study, there was a decrease in the SD of the dosimetric parameters in the IBCL group, and it was statistically significant in change in the variables between 24 hours and 1 month (F-test). The use of IBCL seeds significantly decreased PV₁₅₀, UV₁₅₀, and UD₃₀, and significantly improved HI, without lowering PD₉₀ or PD₁₀₀.

Acute and late toxicities in localized prostate cancer patients treated with low-dose 125I brachytherapy (110 Gy) in combination with external beam radiation therapy versus brachytherapy alone (160 Gy)

Purpose

The aim of this analysis was to compare acute and late toxicities between low-dose-rate brachytherapy (LDR-BT) (110 Gy) in combination with 45 Gy in 25 fractions external beam radiation therapy (EBRT) and LDR-BT (160 Gy) alone for localized prostate cancer.

Material and methods

One hundred five consecutive patients with localized prostate cancer treated from May 2014 to May 2017 were included in this retrospective analysis. Sixty patients received combination therapy and 45 patients received BT monotherapy. The LDR-BT procedure was performed using ¹²⁵I seeds.

Results

The median follow-up time was 28 months in both groups. Three-year effect rates were overall survival: 100% in both groups. The biochemical failure rate was 2.3% in the combination group and 0% in the monotherapy group (p = 0.373). No patients died during the study period. In both groups, almost all the patients experienced acute urethritis. There was a significant difference between the combination therapy group (8.3%) and BT monotherapy group (11.1%) in late genitourinary (GU) toxicities ≥ grade 2 (p = 0.035). Only 2 patients (3.3%) in the combination therapy group developed late ≥ grade 2 rectal hemorrhage. There were no significant differences between two groups in hematuria ≥ grade 2 (p = 0.068) or rectal hemorrhage ≥ grade 2 (p = 0.206).

Conclusions

To our knowledge, this is the first report to compare the GU and gastrointestinal toxicities between the combination therapy and BT monotherapy (160 Gy) for localized prostate cancer. Unexpectedly, there were more late GU toxicities (except for hematuria) in the BT monotherapy group.

Five-year effectiveness of low-dose-rate brachytherapy: comparisons with nomogram predictions in patients with non-metastatic prostate cancer presenting significant control of intra- and periprostatic disease

PURPOSE

To assess the effectiveness of low-dose-rate (LDR) brachytherapy in patients with localized prostate cancer and to compare the outcome with predictions from Kattan and Partin nomograms at 60 months after seed implantation.

MATERIAL AND METHODS

One thousand, one hundred and eighty-seven patients with localized prostate cancer at low-, intermediate-, or high-risk of progression received LDR brachytherapy using iodine-125 seeds with curative intent, applied as monotherapy or in combination with external beam radiation therapy (EBRT), and/or androgen deprivation therapy (ADT). At 60 months after seed implantation, data of 1,064 patients (1,058 alive + 6 who died of prostate cancer) were analyzed for biochemical progression-free survival (bPFS) based on prostate-specific antigen (PSA) levels using the Phoenix definition. Five-year bPFS probabilities were determined for various risk group classifications (d'Amico, Mt. Sinai, MSKCC/Seattle, NCCN). Outcomes were also compared to patient-individualized nomogram predictions of 5-year bPFS (Kattan 2002) and probability of organ-confined disease (Kattan 2002, Partin 2007).

RESULTS

Overall, 93.3% (993/1,064) of the patients were free of biochemical progression within 5 years, while the average 5-year bPFS probability according to the Kattan nomogram was significantly lower (85%, p < 0.001). Outcomes were significantly better than Kattan nomogram predictions in the subgroup of patients with monotherapy as well as in patients additionally treated with EBRT. Comparison of the overall outcome with nomogram predictions for organ-confined disease (Kattan nomogram: 50%; Partin nomogram: 65%) revealed a significant probability of LDR brachytherapy to destroy periprostatic tumor spread (p < 0.001) in all risk group constellations, even in high-risk patients.

CONCLUSIONS

The results indicate high effectiveness of LDR brachytherapy in all risk groups, significantly better than predicted with the Kattan nomogram in most subgroups. The significant superiority of LDR brachytherapy compared to nomogram predictions of organ-confined disease suggests that LDR brachytherapy effectively controls both intra- and periprostatic disease.