Mature Toxicity and Effectiveness Outcomes Associated With Three Treatment Schedules of High-Dose-Rate Brachytherapy Monotherapy for Favorable Risk Prostate Cancer

Document Type

Conference Proceeding

Publication Date

9-2023

Publication Title

Brachytherapy

Abstract

Purpose

To present long-term toxicity and efficacy outcomes of three prostate high-dose-rate (HDR) brachytherapy schedules: 38 Gy in 4 fractions, 24 Gy in 2 fractions, and 27 Gy in 2 fractions for men with low or intermediate risk prostate cancer.

Materials and Methods

Patients treated with HDR brachytherapy monotherapy for prostate cancer from 1999-2020 were identified in a prospectively maintained, single institution database. Patients with AJCC T-stage ≤ T2b, Gleason score ≤ 7, and prostate-specific antigen level ≤ 20 ng/mL were included. Patients with less than two years of follow-up and those treated with single fraction HDR brachytherapy were excluded. Acute and chronic genitourinary (GU) and gastrointestinal (GI) toxicities were defined as side effects occurring ≤ 6 months and ≥ 6 months after radiation therapy, respectively, and were graded according to the Common Terminology Criteria for Adverse Events version 3.0. Biochemical failure was determined using Phoenix criteria. 10-year biochemical control (BC) and local control (LC) rates were estimated using the Kaplan-Meier method. Univariate (UVA) and multivariate analysis (MVA) were performed to determine predictors of biochemical and local failure. Toxicity variables were analyzed with the Chi-squared test.

Results

Six hundred seventy-one patients were included. 310 received 38 Gy in 4 fractions, 129 received 24 Gy in 2 fractions, and 232 were treated with 27 Gy in 2 fractions. Date ranges of treatment for the respective fractionation schedules were 1999-2010, 2007-2016, and 2009-2020 with a median follow-up of 12.8 years, 10.6 years, and 8.1 years (p<0.001), respectively. Two hundred thirty-one (74.5%), 92 (71.3%), and 81 (34.9%) patients (p<0.001) had NCCN low-risk disease, respectively, with the remaining patients having intermediate-risk disease. Upfront androgen deprivation therapy (ADT) was given to 63 (20.3%), 4 (3.1%), and 10 (4.3%) patients (p<0.001), respectively. Respective rates of acute grade ≥ 2 GU toxicity were 11.1%, 12.3%, and 25.0% (p=0.004), while acute grade ≥ 2 GI toxicity was 2.3%, 1.0%, and 1.4% (p=0.74). Rates of chronic grade ≥ 2 GU toxicity were 17.0%, 22.6%, and 26.5% (p=0.06), respectively, while rates of chronic grade ≥ 2 GI toxicity were 1.3%, 1.9%, and 1.6% (p=0.91). For low-risk patients, 10-year rates of BC were 97.8%, 89.3%, and 94.4% (p<0.001), and LC were 99.0%, 94.8%, and 98.0% (p=0.045). For intermediate-risk patients, 10-year BC was 95.8%, 74.2%, and 83.4% (p=0.003), and 10-year LC was 98.4%, 78.7%, and 87.4% (p=0.01), respectively. On UVA, higher pre-treatment PSA, higher Gleason score, 50% or more biopsy cores positive, perineural invasion (PNI), smaller prostate volume, lack of ADT, and 24 Gy or 27 Gy treatment schedules were significant predictors of biochemical failure, and pre-treatment PSA, Gleason score, PNI, and 24 Gy or 27 Gy treatment schedules remained significant on MVA. On UVA, higher pre-treatment PSA, higher Gleason score, PNI, and 24 Gy or 27 Gy treatment schedules were significant predictors of local recurrence, and pre-treatment PSA, PNI, and 24 Gy or 27 Gy treatment schedules remained significant on MVA.

Conclusions

HDR brachytherapy monotherapy with 38 Gy in 4 fractions for favorable-risk prostate cancer was associated with improved long-term BC and LC compared with 24 Gy/27 Gy in 2 fractions, without any associated increase in GI or GU toxicity rates. Prospective evaluation of HDR brachytherapy monotherapy treatment schedules should be considered.

Volume

22

Issue

5 Suppl

First Page

S51

Comments

American Brachytherapy Society Annual Meeting, June 22-24, 2023, Vancouver, British Columbia, Canada

DOI

10.1016/j.brachy.2023.06.076

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