对于寡转移瘤的立体定向消融放疗（SABR），危险器官（OARs）是否应优先于靶区覆盖？基于人群的 II 期 SABR-5 试验的二次分析。
Should organs at risk (OARs) be prioritized over target volume coverage in stereotactic ablative radiotherapy (SABR) for oligometastases? a secondary analysis of the population-based phase II SABR-5 trial.
机构信息
University of British Columbia, British Columbia, Canada; British Columbia Cancer, Kelowna, British Columbia, Canada.
University of British Columbia, British Columbia, Canada; British Columbia Cancer, Surrey, British Columbia, Canada.
出版信息
Radiother Oncol. 2023 May;182:109576. doi: 10.1016/j.radonc.2023.109576. Epub 2023 Feb 22.
BACKGROUND AND PURPOSE
Stereotactic ablative radiotherapy (SABR) for oligometastases may improve survival, however concerns about safety remain. To mitigate risk of toxicity, target coverage was sacrificed to prioritize organs-at-risk (OARs) during SABR planning in the population-based SABR-5 trial. This study evaluated the effect of this practice on dosimetry, local recurrence (LR), and progression-free survival (PFS).
METHODS
This single-arm phase II trial included patients with up to 5 oligometastases between November 2016 and July 2020. Theprotocol-specified planning objective was to cover 95 % of the planning target volume (PTV) with 100 % of the prescribed dose, however PTV coverage was reduced as needed to meet OAR constraints. This trade-off was measured using the coverage compromise index (CCI), computed as minimum dose received by the hottest 99 % of the PTV (D99) divided by the prescription dose. Under-coverage was defined as CCI < 0.90. The potential association between CCI and outcomes was evaluated.
RESULTS
549 lesions from 381 patients were assessed. Mean CCI was 0.88 (95 % confidence interval [CI], 0.86-0.89), and 196 (36 %) lesions were under-covered. The highest mean CCI (0.95; 95 %CI, 0.93-0.97) was in non-spine bone lesions (n = 116), while the lowest mean CCI (0.71; 95 % CI, 0.69-0.73) was in spine lesions (n = 104). On multivariable analysis, under-coverage did not predict for worse LR (HR 0.48, p = 0.37) or PFS (HR 1.24, p = 0.38). Largest lesion diameter, colorectal and 'other' (non-prostate, breast, or lung) primary predicted for worse LR. Largest lesion diameter, synchronous tumor treatment, short disease free interval, state of oligoprogression, initiation or change in systemic treatment, and a high PTV Dmax were significantly associated with PFS.
CONCLUSION
PTV under-coverage was not associated with worse LR or PFS in this large, population-based phase II trial. Combined with low toxicity rates, this study supports the practice of prioritizing OAR constraints during oligometastatic SABR planning.
背景与目的
立体定向消融放疗（SABR）治疗寡转移瘤可能提高生存率，但安全性问题仍令人担忧。为了降低毒性风险，在基于人群的 SABR-5 试验中，SABR 计划优先考虑危及器官（OARs），牺牲了靶区覆盖率。本研究评估了这种做法对剂量学、局部复发（LR）和无进展生存期（PFS）的影响。
方法
这是一项单臂 II 期试验，纳入了 2016 年 11 月至 2020 年 7 月期间最多有 5 个寡转移灶的患者。方案规定的计划目标是将 95%的计划靶区（PTV）用 100%的处方剂量覆盖，但是需要满足 OAR 限制以降低 PTV 覆盖率。通过覆盖率妥协指数（CCI）来衡量这种权衡，CCI 计算为接受最高 99%PTV 的最小剂量（D99）除以处方剂量。低于覆盖范围定义为 CCI＜0.90。评估了 CCI 与结局之间的潜在关联。
结果
共评估了 381 例患者的 549 个病灶。平均 CCI 为 0.88（95%置信区间[CI]，0.86-0.89），196 个病灶（36%）覆盖不足。非脊柱骨病灶的平均 CCI 最高（0.95；95%CI，0.93-0.97），共 116 个病灶；脊柱病灶的平均 CCI 最低（0.71；95%CI，0.69-0.73），共 104 个病灶。多变量分析显示，覆盖不足与较差的 LR（HR 0.48，p=0.37）或 PFS（HR 1.24，p=0.38）无关。最大病灶直径、结直肠和“其他”（非前列腺、乳腺或肺）原发肿瘤与较差的 LR 相关。最大病灶直径、同步肿瘤治疗、无疾病间隔短、寡进展状态、起始或改变全身治疗、PTV Dmax 高与 PFS 显著相关。
结论
在这项大型基于人群的 II 期试验中，PTV 覆盖不足与较差的 LR 或 PFS 无关。结合低毒性发生率，本研究支持在寡转移 SABR 计划中优先考虑 OAR 限制的做法。
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