Howard Thomas P, Ferguson Dianne, Han Zhaohui, Mamon Harvey J, Leeman Jonathan E, van Dams Ritchell
Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts; Harvard Radiation Oncology Program, Boston, Massachusetts.
Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts.
Int J Radiat Oncol Biol Phys. 2025 Jul 1;122(3):752-759. doi: 10.1016/j.ijrobp.2025.03.042. Epub 2025 Mar 31.
Reirradiation in the abdomen poses a challenge due to both interfraction and intrafraction motion of the target and nearby organs at risk. We hypothesized that magnetic resonance-guided stereotactic body radiation therapy (MRgSBRT) with daily online adaptation allows for safe and effective dose-escalated treatment by minimizing grade 3+ gastrointestinal toxicities.
We performed a single-institution retrospective review of 38 patients who received a total of 44 courses of MRgSBRT reirradiation within the abdomen. Clinical outcomes included local control, overall survival, and gastrointestinal toxicities assessed using Common Terminology Criteria for Adverse Events v5. Organs at risk (OAR) metrics of original and adapted plans were compared to assess the added value of daily adaptation.
Fourteen different primary histologies were treated, with the most common including pancreatic (18.2%), renal (18.2%), and prostate (15.9%) cancers. The most common site for reirradiation was abdominal lymph nodes (61.3%). A majority (70.4%) of MRgSBRT courses were preceded by prior stereotactic body radiation therapy. The median and modal prescribed dose of MRgSBRT reirradiation was 40 Gy in 5 fractions (biologically effective dose for α/β = BED = 72); 87% of courses were treated to a biologically effective dose for α/β = 10 of at least 59.5. Across 218 total fractions, daily adaptation improved planning target volume coverage by a mean of 4.1% (95% CI, 3.1%-5.1%, P < .0001) and met 100% of hard luminal gastrointestinal organs at risk 0.03 cc constraints that would have been exceeded without adaptation in 53.2% of fractions. The median follow-up after MRgSBRT reirradiation was 15.8 months. One-year local control and overall survival were 89.5% and 74.9%, respectively. Grade 3+ toxicity possibly related to MRgSBRT reirradiation was observed after 2 (4.5%) courses.
MRgSBRT allows for dose escalation and good local control in cases of abdominal reirradiation with acceptable toxicity. Daily adaptation provided substantial benefits in meeting safety goals and improving coverage. This retrospective study supports the development of a prospective clinical trial of MRgSBRT reirradiation in the abdomen.
腹部再程放疗面临挑战，因为靶区和附近危及器官存在分次间和分次内运动。我们假设，每日在线自适应的磁共振引导立体定向体部放疗（MRgSBRT）通过将3级及以上胃肠道毒性降至最低，可实现安全有效的剂量递增治疗。
我们对一家机构的38例患者进行了回顾性研究，这些患者共接受了44疗程的腹部MRgSBRT再程放疗。临床结局包括局部控制、总生存期，以及使用不良事件通用术语标准第5版评估的胃肠道毒性。比较初始计划和自适应计划的危及器官（OAR）指标，以评估每日自适应的附加价值。
治疗了14种不同的原发组织学类型，最常见的包括胰腺癌（18.2%）、肾癌（18.2%）和前列腺癌（15.9%）。最常见的再程放疗部位是腹部淋巴结（61.3%）。大多数（70.4%）MRgSBRT疗程之前接受过立体定向体部放疗。MRgSBRT再程放疗的中位和模式处方剂量为40 Gy，分5次照射（α/β的生物等效剂量=BED=72）；87%的疗程接受了α/β=10的生物等效剂量至少为59.5。在总共218次分次照射中，每日自适应使计划靶区体积覆盖率平均提高了4.1%（95%CI，3.1%-5.1%，P<.0001），并满足了100%的硬腔胃肠道危及器官0.03 cc的限制，若不进行自适应，53.2%的分次照射会超出该限制。MRgSBRT再程放疗后的中位随访时间为15.8个月。1年局部控制率和总生存率分别为89.5%和74.9%。2个疗程（4.5%）后观察到可能与MRgSBRT再程放疗相关的3级及以上毒性。
MRgSBRT在腹部再程放疗中可实现剂量递增和良好的局部控制，且毒性可接受。每日自适应在实现安全目标和改善靶区覆盖方面提供了显著益处。这项回顾性研究支持开展腹部MRgSBRT再程放疗的前瞻性临床试验。
