Brain Metastasis Growth: What You Need to Know About Preradiosurgical Imaging
"Uncover how preradiosurgical magnetic resonance imaging (MRI) impacts brain metastasis growth and the implications for treatment planning."
Brain metastases represent a significant health challenge, contributing to morbidity and mortality in individuals with advanced cancer. To mitigate the neurocognitive side effects associated with whole brain radiation therapy (WBRT), stereotactic radiation surgery (SRS) has become an increasingly favored approach for managing a limited number of brain metastases.
SRS allows for precise targeting of tumors, but its success depends on accurate imaging. Traditionally, fixed-frame SRS involves same-day MRI planning to ensure accuracy. However, frameless SRS often requires planning MRI to be conducted days or weeks before treatment, potentially impacting the precision due to interval metastasis growth.
A key question arises: does the time lag between the planning MRI and SRS delivery affect local control (LC) due to potential tumor growth? Addressing this concern, a study published in Practical Radiation Oncology sought to quantify brain metastasis growth on MRI scans leading up to SRS, evaluating the need for CTV margins to account for such growth.
Decoding Brain Metastasis Growth: Key Insights from Preradiosurgical MRI
The study, led by Michael A. Garcia and colleagues, retrospectively reviewed data from 165 patients with 411 brain metastases treated with fixed-frame SRS between 2010 and 2013. The researchers compared pretreatment diagnostic brain MRI with SRS-planning MRI scans to quantify volumetric changes in metastases. This comparison allowed for the calculation of growth rates and the determination of minimum margins needed to encompass the entire metastasis on the day of SRS.
- Time Matters: A significant association was found between the time interval between pretreatment and treatment MRI and metastasis growth (P < .001).
- Growth Rate: The mean growth rate was 0.02 ml/day, leading to a 1.35-fold volume increase at 14 days.
- Margin Matters: The time between MRI scans correlated with the amount of margin needed to target the entire brain metastasis volume on the day of SRS (P < .001).
- Additional Factors: Metastasis volume on the pretreatment MRI (P < .001) and melanoma histology (P < .001) also influenced the required margin.
- Local Control: Local control (LC) was not compromised when patients received fixed-frame SRS with same-day MRI planning.
The Future of SRS Planning: Personalizing Margins for Optimal Outcomes
In conclusion, while brain metastasis growth between pretreatment MRI and SRS delivery is a valid concern, it does not compromise local control when employing fixed-frame SRS with same-day MRI planning. The study highlights the importance of considering individual factors such as time interval, tumor size, and histology to personalize treatment planning. By accounting for these variables, clinicians can optimize outcomes in stereotactic radiosurgery for brain metastases, ultimately improving patients' quality of life.