Growth speed of large brain metastases between diagnostic and radiosurgical planning MRI and predictors of rapid tumor growth

We aimed to assess volumetric changes of large brain metastases (≥ 2 cm) between their diagnosis and planning for treatment with fractionated stereotactic radiation surgery (fSRS). Predictors of rapid tumor growth were also analyzed.

One hundred nine patients harboring 126 large brain metastases were retrospectively evaluated. Tumor characteristics were evaluated on diagnostic magnetic resonance imaging (dMRI) and MRI performed when planning fSRS (pMRI). Average tumor growth rate and percentage growth rate were calculated. Predictors of rapid growth (percentage growth rate > 5%) were determined using multivariate logistic regression.

Both tumor diameter and volume were significantly larger on pMRI than on dMRI (P < 0.001). Median tumor percentage growth rate was 2.6% (range, − 10.8–43.3%). Eighty-eight tumors (70%) were slow-growing (percentage growth rate < 5%) and 38 (30%) grew rapidly (percentage growth rate ≥ 5%). Major peritumoral edema and no steroids were predictors of rapid tumor growth.

Large brain metastases can grow considerably between the time of diagnosis and the time of fSRS treatment planning. We recommend the time between dMRI and fSRS treatment initiation be as short as possible.