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.
Radiother Oncol. 2023 May;182:109576. doi: 10.1016/j.radonc.2023.109576. Epub 2023 Feb 22.
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).
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.
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.
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.
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。
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。
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。
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。
