Implications of Identifying Additional Cerebral Metastases during Gamma Knife Radiosurgery

Discovery of increased number or interval growth of brain metastases on same-day GammaKnife™ planning MRI: Predicting factors and patient outcomes

Purpose

To determine factors associated with increased risk of finding new and/or enlarged brain metastases (BM) on GammaKnife™ (GK) MRI and their impact on patient outcomes.

Results

43.9% of patients showed BM growth, 32.9% had additional brain metastases (aBM), and 18.1 % had both. Initial brain metastasis velocity (iBMV) was associated with finding aBM. Time between diagnostic MRI (dMRI) and GK MRI was associated with interval growth and each day increased this risk by 2%. Prior brain metastasectomy and greater time between either dMRI or latest extracranial RT and GK MRI predicted both aBM and BM growth. aBM and/or BM growth led to management change in 1.8% of cases and were not associated with OS or incidence of distant intracranial failure.

Conclusions

Number of metastases seen on dMRI and iBMV predicted both aBM and/or BM growth, however, these factors did not significantly affect survival or incidence of distant intracranial failure.

A nomogram for predicting distant brain failure in patients treated with gamma knife stereotactic radiosurgery without whole brain radiotherapy

BACKGROUND

We review our single institution experience to determine predictive factors for early and delayed distant brain failure (DBF) after radiosurgery without whole brain radiotherapy (WBRT) for brain metastases.

MATERIALS AND METHODS

Between January 2000 and December 2010, a total of 464 patients were treated with Gamma Knife stereotactic radiosurgery (SRS) without WBRT for primary management of newly diagnosed brain metastases. Histology, systemic disease, RPA class, and number of metastases were evaluated as possible predictors of DBF rate. DBF rates were determined by serial MRI. Kaplan-Meier method was used to estimate rate of DBF. Multivariate analysis was performed using Cox Proportional Hazard regression.

RESULTS

Median number of lesions treated was 1 (range 1-13). Median time to DBF was 4.9 months. Twenty-seven percent of patients ultimately required WBRT with median time to WBRT of 5.6 months. Progressive systemic disease (χ(2)= 16.748, P < .001), number of metastases at SRS (χ(2) = 27.216, P < .001), discovery of new metastases at time of SRS (χ(2) = 9.197, P < .01), and histology (χ(2) = 12.819, P < .07) were factors that predicted for earlier time to distant failure. High risk histologic subtypes (melanoma, her2 negative breast, χ(2) = 11.020, P < .001) and low risk subtypes (her2 + breast, χ(2) = 11.343, P < .001) were identified. Progressive systemic disease (χ(2) = 9.549, P < .01), number of brain metastases (χ(2) = 16.953, P < .001), minimum SRS dose (χ(2) = 21.609, P < .001), and widespread metastatic disease (χ(2) = 29.396, P < .001) were predictive of shorter time to WBRT.

CONCLUSION

Systemic disease, number of metastases, and histology are factors that predict distant failure rate after primary radiosurgical management of brain metastases.