Early Volumetric Change and Treatment Outcomes After Palliative Radiation Therapy for Brain Metastasis

Abstract

Purpose/Objective(s): Although brain metastasis is the most common type of brain malignancy, standard treatment scheme still remains uncertain. In this retrospective study, we analyzed early volumetric change and treatment outcomes after radiation therapy (RT) for metastatic brain tumors at our single institution. Materials/Methods: A total of 242 targets (metastatic brain lesions) out of 37 patients were analyzed for this study. We performed co-registration and image fusion of serial MRI on planning CT, and contoured each metastatic lesion to evaluate time-dependent volumetric changes. Influencing factors on local tumor control and dose-response relationship for volumetric reduction of targets were evaluated. RT was delivered by one of the following regimens: Whole brain radiation therapy (WBRT) alone; WBRT+3-dimensional conformal (3D-CRT) boost; Local RT alone; and Tomotherapy-based simultaneous integrated boost (SIB) technique. Most common dose prescription schedule for WBRT was 25 Gy in 10 fractions, and normalized total dose of 1.8 Gy to the target by a/b ratio 10 was 45 (range, 27-64.8) Gy. Most common primary origins were lung followed by breast cancer. Results: Median age of the entire cohorts was 53 (range, 15-82) years. Median number of metastatic lesion was 5 (range, 1-37). Majority of the patients had ECOG performance status scale of 0 to 1 (83.8%) and 24 (64.9%) patients were male. Twenty-three targets out of 16 patients were surgically removed before RT. Among 219 lesions primarily treated with RT, 93.6% of the lesions were controlled at the time of analysis. Six-month local control rate of primary target was 93.4%. CR after RT was achieved in 118 (53.9%) lesions with median 2.8 (range, 0.8-17.1) months. Intracranial progression in other sites developed in nine patients with median 6.9 (range, 1.1-17.5) months. Among 26 patients who had presented with mild to moderate neurologic symptoms, 21 (80.8%) patients improved either by RT or surgery. Tumor volume, initial tumor diameter and tumor histology were major determinants for local control rates. Dose-response analysis revealed that 37 Gy of normalized total dose of 1.8 Gy is required to achieve CR in tumors with less than 1cm in diameter (p < 0.001). Median volume reduction rate at first and second follow-up was 65 and 73.3%, respectively. Conclusions: Palliative RT for brain metastasis is still valuable treatment option in terms of effective tumor control and symptomatic recovery. Our data warrant a larger randomized study to develop more optimized dose prescription schedules depending on tumor size and histology in the radiotherapeutic management of brain metastasis. Author Disclosure: D. Lee: None. Y. Kim: None. C. Lee: None. C. Suh: None. J. Lim: None. H. Kim: None. J. Cho: None.