Background/Objectives: Stereotactic radiotherapy (SABR) is a recognized standard treatment modality for localized prostate cancer, though data is limited regarding the risk of increased toxicity when including the elective nodes (ENI) for high-risk disease. Placement of a peri-rectal spacer can decrease the risk of toxicity to the rectum when administering high-dose prostate radiotherapy. Herein we present toxicity findings for patients who underwent five-fraction prostate SABR with ENI in a setting with peri-rectal spacing.Methods: Genitourinary (GU) and gastrointestinal (GI) toxicity data was analyzed for patients with ≥12 months of follow-up who were treated with curative-intent five-fraction SABR with ENI. A radiopaque hydrogel spacer was placed for all eligible patients. The primary endpoints were the three-month toxicity, which was measured using CTCAEv5, and quality of life (QoL), which was measured using EPIC 26. Secondary endpoints included intermediate-term GU and GI toxicity between 6 and 12 months. Univariable logistic regression was used to assess associations between baseline patient characteristics and the presence of a peri-rectal hydrogel spacer and GU and GI toxicity.Results: Among the 100 patients treated, 69 had grade group 4/5 disease and 40 had evidence of T3a/3b extension. The ENI dose was 25 Gy/5, and 78.9% of the patients received 40 Gy to the prostate, while the remainder were given 36.25–37.5 Gy. A total of 70% underwent placement of a radiopaque hydrogel spacer. GU toxicities of grades 1, 2, and 3 were reported in 28/22/1% of the patients, respectively, at three months; in 18/11/0% at six months; in 11/9/0% at nine months; and in 5/3/0% at twelve months. GI toxicities of grades 1 and 2 were reported in 14/0% of the patients at three months and 8/1% at six months, with all cases resolving by nine months. MCICs in the urinary incontinence, urinary obstructive, and bowel domains were reported in 5%, 18%, and 4% at three months; by twelve months, these values decreased to 2%, 2%, and 0%, respectively. The presence of a hydrogel spacer resulted in reductions in high and intermediate doses to the rectum and had a significant inverse association with short-term GI toxicity (HR: 0.09, CI: 0.27–0.35,p:0.0004).Conclusions: In this prospective series, five-fraction SABR including ENI was well tolerated, and the presence of a hydrogel spacer was associated with a lower risk of rectal toxicity.
背景/目的：立体定向放疗（SABR）是局限性前列腺癌公认的标准治疗方式，但对于高危患者行选择性淋巴结照射（ENI）是否会增加毒性风险的数据有限。在高剂量前列腺放疗中植入直肠周围间隔物可降低直肠毒性风险。本研究旨在探讨接受直肠周围间隔物植入并行五分割前列腺SABR联合ENI治疗患者的毒性反应。 方法：分析随访时间≥12个月、接受根治性五分割SABR联合ENI治疗患者的泌尿生殖系统（GU）和胃肠道（GI）毒性数据。所有符合条件的患者均植入不透射线水凝胶间隔物。主要终点为采用CTCAEv5评估的3个月毒性反应及采用EPIC 26量表评估的生活质量（QoL）。次要终点包括6-12个月的中期GU和GI毒性。采用单变量逻辑回归分析基线患者特征、直肠周围水凝胶间隔物与GU/GI毒性的关联。 结果：在100例接受治疗的患者中，69例为分级组4/5级疾病，40例存在T3a/3b期扩展证据。ENI剂量为25 Gy/5次，78.9%患者前列腺接受40 Gy照射，其余患者接受36.25-37.5 Gy照射。70%患者植入了不透射线水凝胶间隔物。3个月时分别有28%/22%/1%患者出现1/2/3级GU毒性；6个月时为18%/11%/0%；9个月时为11%/9/0%；12个月时为5%/3%/0%。3个月时14%/0%患者出现1/2级GI毒性，6个月时为8%/1%，所有病例在9个月内完全缓解。3个月时尿失禁、尿路梗阻和肠道领域的最小临床重要变化（MCIC）发生率分别为5%、18%和4%；至12个月时分别降至2%、2%和0%。水凝胶间隔物的植入降低了直肠中高剂量照射体积，并与短期GI毒性呈显著负相关（HR: 0.09, CI: 0.27-0.35, p=0.0004）。 结论：在本前瞻性研究中，包含ENI的五分割SABR方案耐受性良好，水凝胶间隔物的植入与直肠毒性风险降低显著相关。
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