2609 - Safety and Feasibility of Simultaneous Integrated Tumor Boost with Hippocampal-Avoidance Whole Brain Radiotherapy for Patients with Brain Metastases
Presenter(s)
S. Jain1, J. E. Schoenhals2, R. Upadhyay3, P. Kumar2, K. Dibs4, W. Zoller5, J. Ghose6, H. K. Perlow7, P. Rajappa8, R. Singh2, S. Beyer2, J. C. Grecula9, D. M. Blakaj10, A. Chakravarti11, E. M. Thomas2, J. D. Palmer2, and R. Raval2; 1The Ohio State University College of Medicine, Columbus, OH, 2Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Columbus, OH, 3Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Columbus, OH,, Columbus, OH, 4The Ohio State University Wexner Medical Center, Columbus, OH, 5Department of Radiation Oncology, The James Cancer Center, Ohio State University Wexner Medical Center, Columbus, OH, 6The Ohio State University, Columbus, OH, 7Department of Radiation Oncology, University Hospitals Seidman Cancer Center, Case Western Reserve University, Cleveland, OH, 8Nationwide Children's Hospital, The Ohio State University College of Medicine, Columbus, OH, 9Department of Radiation Oncology, James Cancer Hospital/Wexner Medical Center, The Ohio State University, Columbus, OH, 10Department of Radiation Oncology, James Cancer Hospital, The Ohio State University, Columbus, OH, 11The Ohio State University Comprehensive Cancer Center, Columbus, OH
Purpose/Objective(s): Survival of patients with brain metastases has improved with advances in systemic therapy and radiation techniques. Hippocampal avoidance whole brain radiation (HA-WBRT) is the current standard of care for patients with significant intracranial metastatic burden. Although WBRT offers similar survival outcomes compared to stereotactic radiosurgery (SRS), local control rates are often poor. This could potentially be attributed to a lower biological equivalent dose (BED) associated with WBRT (30 Gy in 10 fractions is equivalent to 39 Gy) vs SRS (18 Gy in 1 fraction is equivalent to 50 Gy). We hypothesize that by delivering a higher BED through a simultaneous integrated boost technique (SIB) to 35 Gy (BED 47.25 Gy) to the physical tumor volume, we can improve intracranial control. Our study was aimed at evaluating the safety and feasibility of HA-WBRT with a simultaneous integrated boost (SIB) to brain metastases.
Materials/Methods: Patients who underwent HA-WBRT from 2021 - 2024 were included in the study. Gross tumor volume (GTV) was contoured as one structure on fused post-contrast T1 volumetric MRI scans encompassing all visible metastatic lesions. Radiation was planned using a volumetric modulated arc therapy (VMAT) technique with an SIB of 35 Gy to the GTV with no additional margin. Dose constraints for the hippocampal avoidance structure included a D100% = 9 Gy and D0.03 cm3 = 16 Gy. Hippocampal avoidance was prioritized over SIB coverage of brain metastases. Primary endpoint was = grade 3 toxicity. Secondary endpoints were freedom from intracranial progression and overall survival (OS). Kaplan-Meier method was used for survival analyses.
Results: A total of 25 patients treated with HA-WBRT + SIB were included in the study. Median age was 64 years (27-80) and the most common primary tumor type was lung (48%), followed by breast (20%) and melanoma (16%). 48% of patients had prior SRS, while 8% received subsequent SRS after HA-WBRT. All patients received a HA-WBRT dose of 30 Gy in 10 fractions with a SIB of 35 Gy in 10 fractions. The median GTV volume was 8.4 cc (range 0.7 - 118.2). The median Dmean to the GTV was 36.3 Gy (range 35.5 - 42.6). Average hippocampus D100 and D0.03 cc doses were 8.2 and 15.4 Gy, respectively. Median follow-up for surviving patients was 9.3 months. None of the patients developed any = grade 3 or higher toxicities. Of the 25 patients, 5 experienced intracranial progression at a median time of 131 days (range 16-211). Median OS was 4.5 months (95% CI 3.9-5.1m), with 6- and 12-month OS of 45% and 37%.
Conclusion: We report a novel radiation technique for brain metastases patients with significant metastatic burden undergoing HA-WBRT. Utilizing SIB with VMAT, we were able to escalate the GTV dose to 35 Gy (BED ~ 47 Gy) with minimal toxicity and excellent intracranial control. Prospective studies to validate our findings are warranted.