Aims

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.

Materials and methods

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.

Results

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.

Conclusions

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.

中文翻译：

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局部复发性直肠癌等毒再照射立体定向消融体放疗的潜力

目标

局部复发性直肠癌 (LRRC) 的非手术治疗是一个需求未得到满足的领域，没有明确的标准治疗方法和极差的结果。患者通常在初始多模式治疗期间接受放射治疗，并且历史上的再照射仅限于保守剂量，随后短期症状得到控制。最近，立体定向消融体放射治疗 (SABR) 已在英格兰 LRRC 的再照射中显示出前景，但仅限于相对适中的 30Gy 剂量处方，分 5 次。我们建议使用等毒剂量处方在 LRRC 中实现 SABR 至更高剂量，该处方具有每年固定 15% 的组织恢复率，可接受的风险器官 (OAR) 限制。

材料和方法

对在当地中心接受 SABR 再照射治疗的 LRRC 患者进行了审核。确定患者，确定自先前放疗以来的剂量和时间，计算再照射 OAR 限制并进行回顾性重新计划。

结果

在目前接受 SABR 的患者（17 名患者，21 个目标）中，可实现 5 次剂量增加至 30 Gy 以上，80 Gy（α/β = 10）的生物有效剂量可递送至计划目标体积的 80% 或更多在 21 个目标中的 8 个。

结论

等毒 SABR 再照射应被视为 LRRC 的潜在治疗选择，以最大限度地提高患者预后，同时限制过度毒性。尽管可能是保守的，但需要临床结果数据来确定使用每年 15% 的组织恢复的 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 的总体存活率的影响。