Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
Division of Neurosurgery, St Michaels Hospital, University of Toronto, Toronto, Ontario, Canada.
Int J Radiat Oncol Biol Phys. 2019 Oct 1;105(2):394-399. doi: 10.1016/j.ijrobp.2019.06.2543. Epub 2019 Jul 5.
To compare normal tissue dosimetry between hippocampal-avoidance whole brain radiation therapy (HA-WBRT) and stereotactic radiosurgery (SRS) in patients with 10 to 30 brain metastases, and to describe a novel SRS strategy we term Spatially Partitioned Adaptive RadiosurgEry (SPARE).
A retrospective review identified SRS treatment plans with >10 brain metastases located >5 mm from the hippocampi. Our Gamma Knife Icon (GKI) SPARE (GKI-Spr) technique treats multiple metastases with single-fraction SRS partitioned over consecutive days while limiting the total treatment time to ≤60 minutes per day. Hippocampal and normal brain dosimetry were compared among GKI-Spr, single-fraction single-day GKI (GKI-Sfr), and 30 Gy in 10 fractions HA-WBRT. Dose metrics were converted to equivalent dose in 2 Gy fractions.
Ten cases were analyzed. Compared with HA-WBRT, GKI-Spr significantly reduced the median equivalent dose in 2 Gy fractions hippocampal maximum point dose, mean dose, and dose to 40% of the hippocampi (D40%) by 86%, 93%, and 93%, respectively, and similarly for GKI-Sfr by 81%, 92%, and 91%, respectively. The normal brain median mean dose was reduced by 95% with GKI-Spr and 94% with GKI-Sfr. Compared with GKI-Sfr, GKI-Spr further reduced all normal brain and hippocampal dose metrics (P ≤ .014).
GKI yields superior hippocampal and normal brain dosimetry compared with HA-WBRT, and GKI-Spr results in further dosimetric advantages.
比较 10 至 30 个脑转移瘤患者行海马回避全脑放疗（HA-WBRT）和立体定向放疗（SRS）的正常组织剂量学，描述一种新的 SRS 策略，我们称之为空间分区自适应放疗（SPARE）。
回顾性分析了>10 个位于距海马>5mm 的脑转移瘤的 SRS 治疗计划。我们的伽玛刀 Icon（GKI）SPARE（GKI-Spr）技术采用单次分割，连续多天治疗多个转移灶，同时将每天的总治疗时间限制在≤60 分钟。比较了 GKI-Spr、单次分割单次治疗的 GKI（GKI-Sfr）和 30Gy/10 次分割的 HA-WBRT 之间的海马和正常脑剂量学。剂量指标转换为等效剂量 2Gy 分数。
分析了 10 例患者。与 HA-WBRT 相比，GKI-Spr 使海马最大点剂量、平均剂量和 40%海马剂量（D40%）的等效剂量 2Gy 分数分别降低了 86%、93%和 93%，GKI-Sfr 分别降低了 81%、92%和 91%。GKI-Spr 和 GKI-Sfr 使正常脑平均剂量中位数降低了 95%和 94%。与 GKI-Sfr 相比，GKI-Spr 进一步降低了所有正常脑和海马的剂量指标（P≤.014）。
GKI 与 HA-WBRT 相比，具有更好的海马和正常脑剂量学，而 GKI-Spr 则具有进一步的剂量学优势。
