Stereotactic radiosurgery (SRS) for multiple metastatic brain tumors: effects of the number of target tumors on exposure dose in normal brain tissues.
ABSTRACT This study was carried out to clarify the practical limit of the number of stereotactic radiosurgery (SRS)-targeted tumors based on the irradiation dose of normal brain tissues.
Twenty-five patients with multiple brain metastases who received SRS from October 1998 to May 2002 were enrolled in the study. In each patient, the treatment options were thoroughly studied before deciding upon a course of treatment. The number of irradiated targets was increased one by one until all of the targets were included in a treatment plan. Given a surface dose of 25 Gy, we calculated the dose volume histogram (DVH) for the entire brain in each treatment plan and compared it with those of other treatment plans. Ultimately, only 5 of the 25 patients received irradiation for all of their tumors; the others received selective irradiation targeting only those tumors that were causing symptoms.
When the number of targets increased, the DVH curve shifted to the right. The volume of the brain irradiated at a dose of 5 Gy or higher was 25.7% or less for 4 or fewer targets, 45.7% for 5-6 targets, 81.0% for 7-8 targets and 100% for 9-11 targets. When the number of the targets exceeded 8, more than 50% of the entire brain was irradiated at levels of at least 8.7 Gy. The dose distribution became very complex as the number of targets increased. Although the survival time of the group in which tumors were selectively targeted was longer than that in the group in which all tumors were irradiated, the difference between the two groups was not statistically significant ( P = 0.2537).
In SRS for multiple brain metastases, risks of both acute and late sequelae may increase because the exposure dose to normal brain tissues increases with increased numbers of target tumors. Dose distribution becomes more complex according to the increase in the number of targets. Based on our DVH curves, we conclude that the exposure dose to normal brain tissues is acceptable when the number of targets is less than 7. Importantly, our study also reveals that it may not be necessary or desirable to irradiate all metastatic tumors.
SourceAvailable from: Constantine Kaniklidis
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ABSTRACT: CNS metastasis from breast cancer, either to the brain or in the form of leptomeningeal metastasis (“neoplastic meningitis”), represents an exceptional therapeutic challenge given its associated compromised prognosis and the practical problems of crossing the blood-brain and cerebrospinal barriers with sufficient penetrance and resident activity to provide clinically meaningful benefit. However, we argue here that new and emerging breakthroughs in our understanding of the biological and molecular “architectures” of metastases and of CNS metastases in particular, along with data evidencing a class of clinically realistic cross-BBB and cross-CSF agents, coupled with advances in local treatment via radiotherapies and stereotactic radiosurgery (SRS) among others, has led to corresponding new hope and promise in optimizing the effective treatment of CNS metastases and in improving survival outcomes
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ABSTRACT: To determine feasibility of RapidArc in sequential or simultaneous integrated tumor boost in whole brain radiation therapy (WBRT) for poor prognostic patients with four or more brain metastases. Nine patients with multiple (≥4) brain metastases were analyzed. Three patients were classified as class II in recursive partitioning analysis and 6 were class III. The class III patients presented with hemiparesis, cognitive deficit, or apraxia. The ratio of tumor to whole brain volume was 0.8-7.9%. Six patients received 2-dimensional bilateral WBRT, (30 Gy/10-12 fractions), followed by sequential RapidArc tumor boost (15-30 Gy/4-10 fractions). Three patients received RapidArc WBRT with simultaneous integrated boost to tumors (48-50 Gy) in 10-20 fractions. The median biologically effective dose to metastatic tumors was 68.1 Gy(10) and 67.2 Gy(10) and the median brain volume irradiated more than 100 Gy(3) were 1.9% (24 cm(3)) and 0.8% (13 cm(3)) for each group. With less than 3 minutes of treatment time, RapidArc was easily applied to the patients with poor performance status. The follow-up period was 0.3-16.5 months. Tumor responses among the 6 patients who underwent follow-up magnetic resonance imaging were partial and stable in 3 and 3, respectively. Overall survival at 6 and 12 months were 66.7% and 41.7%, respectively. The local progression-free survival at 6 and 12 months were 100% and 62.5%, respectively. RapidArc as a component in whole brain radiation therapy for poor prognostic, multiple brain metastases is an effective and safe modality with easy application.06/2012; 30(2):53-61. DOI:10.3857/roj.2012.30.2.53