Radiotherapy for Clinically Localized T3b or T4 Very-High-Risk Prostate Cancer-Role of Dose Escalation Using High-Dose-Rate Brachytherapy Boost or High Dose Intensity Modulated Radiotherapy

Hideya Yamazaki,Haruumi Okabe,Takuya Kimoto,Satoaki Nakamura,Daisuke Shimizu,Ken Yoshida,Gen Suzuki,Koji Masui,Norihiro Aibe

doi:10.3390/cancers13081856

Hideya Yamazaki, Haruumi Okabe + Show 7 more

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https://doi.org/10.3390/cancers13081856

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Abstract

Simple SummaryRecently, high-risk prostate cancer was subdivided to a very-high-risk group considered to have the worst prognosis, including clinical stage T3b–T4, primary Gleason pattern 5, or more than four biopsy cores with Gleason score 8–10. Among these, T3b–T4 stage is a special interest in radiotherapy because of their wider target volume outside the prostate. We examined this subgroup and found that dose escalation in radiotherapy both with brachytherapy or intensity modulated radiotherapy (IMRT) improved biochemical free survival rate but not in prostate cancer specific survival rate and overall survival rate.To examine the efficacy of dose escalating radiotherapy into patients with cT3b or T4 localized prostate cancer, we compared Group A (86 conventional dose external beam radiotherapy: EBRT group, treated with 70–72 Gy) and group B (39 high dose EBRT group (HDEBRT group, 74–80 Gy) and 124 high-dose-rate brachytherapy (HDR) + EBRT (HDR boost)) using multi-institutional retrospective data. The actuarial 5-year biochemical disease-free survival (bDFS) rate, prostate cancer specific survival rate (PSS), and overall survival rate (OS) were 75.8%, 96.8%, and 93.5%. Group B showed superior 5-year bDFS rate (81.2%) as compared to the group A (66.5%) (p < 0.0001) with a hazard ratio of 0.397. Equivocal 5-year PSS (98.3% and 94.8% in group B and group A) and OS (both 93.7%) were found between those groups. Accumulated late grade ≥ 2 toxicities in gastrointestinal and genitourinary tracts were similar among those three groups. Therefore, both HDEBRT and HDR boost could be good options for improving the bDFS rate in cT3–T4 localized prostate cancer without affecting PSS and OS.

Highlights

With modern imaging and techniques, we could speculate that high dose rate brachytherapy (HDR) could potentially treat the T3b–4 diseases that had invaded outside the prostate [10], and we examined the outcome of HDR boost in cT3b–4 prostate cancer
We examined the data of patients treated with HDR boost [11] and external beam radiotherapy (EBRT) in a retrospective fashion (Table 1)
high dose EBRT (HDEBRT)), and BED/EQD2Gy for each treatment were shown in Tables S1 and S2

Summary

Introduction

Prostate cancer is the most common solid organ malignancy in men in developed countries [1], and the second leading cause of cancer death in the United States of America (USA) [1]. Advanced treatments have improved outcome, it has become difficult to choose the best treatment modality because there are many curative treatment options, such as surgery, external beam radiotherapy (EBRT), and brachytherapy (BT) [2]. High-risk prostate cancer was recently subdivided to include a very-high-risk group considered to have the worst prognosis, including clinical stage T3b–T4, primary Gleason pattern 5, or more than four biopsy cores with Gleason score 8–10 [2].

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