ESTRO 2024 - Abstract Book

S763

Clinical - CNS

ESTRO 2024

using the Kaplan-Meier method. Univariable analyses were conducted using the log-rank test. Predictors of disease outcomes were investigated using multivariable Cox regression.

Results:

Sixty-nine patients fulfilled the inclusion criteria. The median follow-up period was 40 months. The number of patients in RPA class I, II and III were 14 (20.3%), 42 (60.9%) and 13 (18.8%) respectively. Predominant cancer subtypes included lung (N = 41, 59.4%) and breast (N = 14, 20.3%). Most patients underwent gross total excision (N = 55, 79.7%). The mean maximum tumour diameter was 3.5cm (SD, 1.2cm). The majority of tumours were supratentorial (N = 54, 78.3%) and had dural involvement on pre-operative MRI (N = 49, 71%). Most patients received SRS in 30Gy / 5Fr (N = 51, 73.9%), followed by 18Gy / 1Fr (N = 5, 7.2%), 25Gy / 5Fr (N = 4, 5.8%), and 27.5Gy / 5Fr (N = 3, 4.3%). The median target and treatment volume was 7.12cc (IQR, 10.53cc) and 9.85cc (IQR, 13.0cc), respectively. The mean conformity index was 1.39 (SD, 0.16). The 1-year LCR and DBCR were 63.5% and 51.1%, respectively. The median and 1-year LRFS were 15 months and 53.1%, respectively. The median and 1-year OS for our cohort were 21 months and 72.1%, respectively. Eleven patients experienced dural relapse (1-year dural relapse rate, 20.8%). On multivariable analysis, high BED10 was a significant independent factor associated with superior local control (hazard ratio, 0.885; 95% C.I., 0.799 - 0.982; p = 0.021). Cavities that received BED10 > 45Gy had superior local control than those that received BED10 ≤ 45Gy (1 -year LCR, 70.0% vs. 18.8%; p = 0.018). No high-grade radiation-associated adverse events were detected.

Conclusion:

We report characteristics and outcomes of resection cavity SRS in a real-world cohort. LCR of resection cavity SRS for brain metastases was lower than that reported in the literature. Radiation dose higher than BED10 45Gy was associated with superior outcomes and should be enforced if dosimetric safety of organs at risk are fulfilled.

Keywords: SRS, cavity, brain metastasis

References:

Gondi V, Bauman G, Bradfield L, et al. Radiation therapy for brain metastases: an astro clinical practice guideline. Pract Radiat Oncol. 2022;12(4):265-282.

Mahajan A, Ahmed S, McAleer MF, et al. Post-operative stereotactic radiosurgery versus observation for completely resected brain metastases: a single-centre, randomised, controlled, phase 3 trial. Lancet Oncol. 2017;18(8):1040 1048. Brown PD, Jaeckle K, Ballman KV, et al. Effect of radiosurgery alone vs radiosurgery with whole brain radiation therapy on cognitive function in patients with 1 to 3 brain metastases: a randomized clinical trial. JAMA. 2016;316(4):401-409. Brown PD, Ballman KV, Cerhan JH, et al. Postoperative stereotactic radiosurgery compared with whole brain radiotherapy for resected metastatic brain disease (Ncctg n107c/cec·3): a multicentre, randomised, controlled, phase 3 trial. Lancet Oncol. 2017;18(8):1049-1060.