Oxford University Hospitals NHS Trust, Oxford, UK; Department of Oncology, University of Oxford, Oxford, UK.
Institute of Cancer Sciences, University of Glasgow, Glasgow, UK; Beatson West of Scotland Cancer Centre, Glasgow, UK.
Clin Oncol (R Coll Radiol). 2022 Sep;34(9):571-577. doi: 10.1016/j.clon.2022.04.007. Epub 2022 Apr 30.
The non-surgical management of locally recurrent rectal cancer (LRRC) is an area of unmet need, with no defined standard treatment and extremely poor outcomes. Patients typically receive radiotherapy during initial multimodality treatment and historically re-irradiation has been limited to conservative doses with subsequent short-term symptom control. Recently, stereotactic ablative body radiotherapy (SABR) has shown promise in re-irradiation of LRRC in England, but is limited to a relatively modest dose prescription of 30Gy in five fractions. We propose that SABR can be achieved in LRRC to higher doses using an isotoxic dose prescription with fixed 15% per annum tissue recovery for acceptable organ at risk (OAR) constraints.
Patients with LRRC at a local centre treated with SABR re-irradiation were audited. Patients were identified, the dose and time since previous radiotherapy determined, re-irradiation OAR constraints calculated and retrospective re-planning carried out.
In patients currently receiving SABR (17 patients, 21 targets), dose escalation above 30 Gy in five fractions was achievable, with a biological effective dose of 80 Gy (alpha/beta = 10) deliverable to 80% or more of the planning target volume in eight of the 21 targets.
Isotoxic SABR re-irradiation should be considered a potential treatment option for LRRC to maximise patient outcomes while limiting excess toxicity. Although probably conservative, clinical outcome data are needed to determine the suitability of OAR constraints using 15% per annum tissue recovery and the impact on local control rates, patient quality of life and overall survival of isotoxic SABR.
局部复发性直肠癌（LRRC）的非手术治疗是一个未满足的需求领域，目前尚无明确的标准治疗方法，治疗效果极差。患者在初始多模式治疗期间通常接受放疗，并且历史上再放疗仅限于保守剂量，随后进行短期症状控制。最近，立体定向消融体放射治疗（SABR）在英国复发性 LRRC 再放疗方面显示出了希望，但仅限于相对适度的 30Gy 剂量处方，分为 5 个分数。我们提出，使用固定的 15%每年组织恢复的等效剂量处方，SABR 可以在 LRRC 中实现更高的剂量，以达到可接受的危及器官（OAR）限制。
对在当地中心接受 SABR 再放疗的 LRRC 患者进行了审核。确定了患者，确定了剂量和上次放疗的时间，计算了再放疗 OAR 限制，并进行了回顾性再计划。
在目前接受 SABR 治疗的患者中（17 例患者，21 个靶区），可以实现超过 30Gy 分 5 次的剂量升级，21 个靶区中有 8 个靶区的生物有效剂量为 80Gy（α/β=10），可达到 80%或更多的计划靶区体积。
等毒 SABR 再放疗应被视为 LRRC 的一种潜在治疗选择，以最大限度地提高患者的治疗效果，同时限制过度毒性。尽管可能比较保守，但需要临床结果数据来确定使用 15%每年组织恢复的 OAR 限制的适用性，以及对局部控制率、患者生活质量和等毒 SABR 总体生存率的影响。
