Department of Radiation Oncology, H. Lee Moffitt Cancer Center & Research Institute, Tampa FL, USA.
Cancer Control. 2024 Jan-Dec;31:10732748241270595. doi: 10.1177/10732748241270595.
Stereotactic body radiotherapy (SBRT) is widely used for localized prostate cancer and implementation of MR-guided radiotherapy has the advantage of tighter margins and improved sparing of organs at risk. Here we evaluate outcomes and time required to treat using non-adaptive MR-guided SBRT (MRgSBRT) for localized prostate cancer at our institution.
From 9/2019 to 11/2021 we conducted a retrospective review of 80 consecutive patients who were treated with MRgSBRT to the prostate. Patients included low (LR) (5%), favorable intermediate (FIR) (40%), unfavorable intermediate (UIR) (49%), and high risk (HR) (6%). Short-term androgen deprivation therapy was used in 32% of patients. Target volumes included prostate gland and proximal seminal vesicles with an isotropic 3 mm margin. Treatment was prescribed to 36.25 Gy in 5 fractions every other day with urethral sparing. Hydrogel spacer was used in 18% of patients. Time on the linac was recorded as beam on time (BOT) plus total treatment time (TTT) including gating. Analyzed outcomes included PSA response and patient reported outcomes scored by the American Urological Association (AUA) questionnaire and toxicity per CTCAE v5. General linear regression model was used to analyze factors affecting PSA and AUA in longitudinal follow up, and chi-square test was used to assess factors affecting toxicity.
Median follow up was 19.3 months (3.8 - 36.6). Median BOT was 4.6 min (2.6 - 7.2) with a median TTT of 11 min (7.6 - 15.8). Pre-treatment vs post-RT median PSA was 6.36 (2.20 - 19.6) vs 0.85 (0.19 - 3.6), respectively ( < 0.001). PSA decrease differed significantly when patients were stratified by risk category, favoring LR/FIR vs UIF/HR group ( = 0.019). Four (5%) patients experienced a biochemical failure (BCF), with a median time to BCF of 20.4 months (7.9 - 34.5). Median biochemical failure free survival (BCFFS) was not reached, with 2-yr and 4-yr BCFFS of 97.1% and 72.1%, respectively. Patients with LR/FIR disease had 100% 2-yr and 4-yr BCFFS, whereas patients with UIF/HR had 95% and 41% 2-yr and 4-yr BCFFS ( = 0.05). Mean pre-treatment AUA was 7.3 (1 - 25) vs 11.3 (1 - 26) at first follow-up; however, AUA normalized to baseline over time. Urethral Dmax ≥35 Gy trended to lower AUA score at all follow-ups ( = 0.07). Forty-one (51%) patients reported grade 1-2 genitourinary toxicities at the 1 month follow up. Grade 3 toxicity (proctitis) was noted in 1 patient. There was no decrease in any grade rectal toxicity with use of hydrogel spacer (3 vs 6, = 0.2). No grade ≥4 toxicities was observed.
MRgSBRT has the potential for treatment adaptation but this comes at the cost of increased resource utilization. Our experience with non-adaptive MRgSBRT of the prostate highlights its short treatment times as well as efficacy with good PSA control and low toxicity profile.
立体定向体放射治疗（SBRT）广泛用于局部前列腺癌，而实施磁共振引导放射治疗的优势在于更严格的边缘和更好地保护危险器官。在这里，我们评估了在我们机构使用非适应性磁共振引导 SBRT（MRgSBRT）治疗局部前列腺癌的结果和所需时间。
从 2019 年 9 月至 2021 年 11 月，我们对 80 例连续接受 MRgSBRT 治疗的前列腺癌患者进行了回顾性分析。患者包括低危（LR）（5%）、低中危（FIR）（40%）、中高危（UIR）（49%）和高危（HR）（6%）。32%的患者接受了短期雄激素剥夺治疗。靶区包括前列腺和近端精囊，各向同性 3mm 边界。采用 5 次隔日 36.25Gy 处方剂量，同时保留尿道。18%的患者使用了水凝胶间隔器。记录在线加速器上的时间为射束开启时间（BOT）加包括门控在内的总治疗时间（TTT）。分析结果包括 PSA 反应和美国泌尿外科学会（AUA）问卷评分的患者报告结果以及按 CTCAE v5 评估的毒性。采用一般线性回归模型分析影响 PSA 和 AUA 纵向随访的因素，采用卡方检验分析影响毒性的因素。
中位随访时间为 19.3 个月（3.8-36.6）。中位 BOT 为 4.6 分钟（2.6-7.2），中位 TTT 为 11 分钟（7.6-15.8）。治疗前与治疗后中位 PSA 分别为 6.36（2.20-19.6）和 0.85（0.19-3.6）（<0.001）。当患者按风险类别分层时，PSA 降低差异具有统计学意义，LR/FIR 组优于 UIF/HR 组（=0.019）。4 例（5%）患者发生生化失败（BCF），中位 BCF 时间为 20.4 个月（7.9-34.5）。中位生化无失败生存（BCFFS）未达到，2 年和 4 年 BCFFS 分别为 97.1%和 72.1%。LR/FIR 疾病患者的 2 年和 4 年 BCFFS 均为 100%，而 UIF/HR 疾病患者的 2 年和 4 年 BCFFS 分别为 95%和 41%（=0.05）。治疗前平均 AUA 为 7.3（1-25），首次随访时为 11.3（1-26）；然而，AUA 随着时间的推移逐渐恢复到基线水平。所有随访时，尿道 Dmax≥35Gy 与较低的 AUA 评分趋势相关（=0.07）。41 例（51%）患者在 1 个月随访时报告有 1-2 级泌尿生殖毒性。1 例患者出现 3 级毒性（直肠炎）。使用水凝胶间隔器并没有降低任何级别的直肠毒性（3 例 vs 6 例，=0.2）。未观察到任何≥4 级毒性。
MRgSBRT 有治疗适应的潜力，但这是以增加资源利用为代价的。我们使用非适应性 MRgSBRT 治疗前列腺癌的经验强调了其治疗时间短，PSA 控制良好，毒性谱低的优势。
