2637 - The Eurytopic Paradigm of Simultaneous Integrated Boost Volumetric Modulated Arc Radiotherapy for Brain Metastases: A Phase Ib/II Clinical Trial

M. Wu¹, D. Liu¹, Y. Hu¹, C. Wang¹, Y. Liu², Y. Ma¹, Z. Hu¹, Z. Wang¹, W. Zhang³, K. Li⁴, S. Yao¹, Y. Liu¹, and G. Zhao¹; ¹Department of Radiation Oncology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ²Department of Neurosurgery, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ³Clinical Research Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China, ⁴Department of Radiology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Purpose/Objective(s): Stereotactic radiosurgery (SRS) is widely used for brain metastases but still has some limitations in clinical practice, including tumor size, numbers of lesions. This prospective study was aimed to explore the use of whole brain radiotherapy (WBRT) plus a higher dose simultaneous integrated boost (SIB) radiotherapy techniques, further improving local control and quality of life (QOL) of patients. Materials/

Methods: Patients pathological confirmation of extracerebral tumor site other than breast cancer or small cell lung cancer malignancy were enrolled in this prospective study. Main exclusion criteria were contraindications to MRI scan, inability to complete position fixation for radiotherapy, and lesion located within 4mm of the optic chiasm or within the brainstem. Patients were treated with WBRT plus SIB using volumetric modulated arc therapy (VMAT). The total biological effective dose (BED) for the gross disease receiving a SIB boost was prescribed 71.6-86Gy with a/ß=10Gy. Systemic therapy before and after RT for brain metastases was permitted. The primary endpoint is intracranial lesion control rate at six months post-radiation. Secondary endpoint was intracranial progression free survival (PFS), overall survival (OS), toxic effects, cognitive function and QOL assessments. The study was approved by the institutional review board and registered at Chictr.org.cn: ChiCTR1900026794. All patients provided written informed consent.
Results: A total of forty-eight patients were enrolled. The primary tumor of the majority patients (81.3%, 39/48) was non-small cell lung cancer. The 6-months intracranial disease control rate was 79.2% (38/48). The median intracranial PFS and OS was 12.6 months and 18.2 months. Patients with brain metastases =3 had a shorter median intracranial PFS (8.3 months vs. 18.2 months, p = 0.044). In lung cancer patients, the 2-year intracranial PFS rates of EGFR-TKIs therapy compared with no EGFR-TKIs therapy were 53.6% and 11.0%, respectively (p = 0.026). No adverse reactions above grade 3 were observed. There was no significant decline in cognitive function and QOL after radiotherapy.
Conclusion: Among patients with one to ten brain metastases, WBRT with SIB achieved encouraging intracranial control rate and was well-tolerated with acceptable toxicities. This treatment strategy may provide an alternative for patients harboring within ten intracranial lesions.