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Total target volume is a better predictor of whole brain dose from gamma stereotactic radiosurgery than the number, shape, or location of the lesions

PURPOSE

To assess the hypothesis that the volume of whole brain that receives a certain dose level is primarily dependent on the treated volume rather than on the number, shape, or location of the lesions. This would help a physician validate the suitability of GammaKnife(®) based stereotactic radiosurgery (GKSR) prior to treatment.

METHODS

Simulation studies were performed to establish the hypothesis for both oblong and spherical shaped lesions of various numbers and sizes. Forty patients who underwent GKSR [mean age of 54 years (range 7-80), mean number of lesions of 2.5 (range 1-6), and mean lesion volume of 4.4 cm(3) (range 0.02-22.2 cm(3))] were also studied retrospectively. Following recommendations of QUANTEC, the volume of brain irradiated by the 12 Gy (VB12) isodose line was measured and a power-law based relation is proposed here for estimating VB12 from the known tumor volume and the prescription dose.

RESULTS

In the simulation study on oblong, spherical, and multiple lesions, the volume of brain irradiated by 50%, 10%, and 1% of maximum dose was found to have linear, linear, and exponentially increasing dependence on the volume of the treated region, respectively. In the retrospective study on 40 GKSR patients, a similar relationship was found to predict the brain dose with a Spearman correlation coefficient >0.9. In both the studies, the volume of brain irradiated by a certain dose level does not have a statistically significant relationship (p ≥ 0.05) with the number, shape, or position of the lesions. The measured VB12 agrees with calculation to within 1.7%.

CONCLUSIONS

The results from the simulation and the retrospective clinical studies indicate that the volume of whole brain that receives a certain percentage of the maximum dose is primarily dependent on the treated volume and less on the number, shape, and location of the lesions.

Fifty percent patients avoid whole brain radiotherapy: stereotactic radiotherapy for multiple brain metastases: a retrospective analysis of a single center

PURPOSE

To summarize the outcomes of stereotactic radiotherapy (SRT), with or without whole-brain radiotherapy (WBRT), in the treatment of multiple brain metastasis and to explore the status of WBRT and SRT in the management of multiple brain metastasis.

METHODS

From May 1995 to April 2010, 98 patients with newly diagnosed, multiple brain metastasis were treated in our center. Forty-four patients were treated with SRT alone for the initial treatment, and 54 were treated with SRT + WBRT. Kaplan-Meier and Cox proportional hazards regression analyses were used for the survival analysis.

RESULTS

The median survival time (MST) was 13.5 months. No difference was observed in MST between the SRT and the SRT + WBRT groups (p = 0.578). The Karnofsky Performance Score at the time of treatment (p = 0.025), the interval time between diagnosis of primary tumor and brain metastasis (P = 0.012) and the situation of extracranial disease (p = 0.018) were significant predictors of survival. The crude distant intracranial recurrence (DIR) rates were 47.7 % in the SRT group and 24.1 % in the SRT + WBRT group (p = 0.018). In addition, 52.3 % patients in the SRT group were free from DIR and did not require WBRT in their whole lives.

CONCLUSIONS

Our data suggest that use of SRT as the initial treatment while reserving WBRT as the salvage therapy in case of distant intracranial recurrence made about 50 % of the patients avoid WBRT throughout the course of their lives and may be another optional treatment modality for multiple brain metastases.

Evolving management of newly diagnosed brain metastases: expanding role of radiosurgery in lieu of whole brain radiation

The use of stereotactic radiosurgery has grown increasingly prevalent in the management of patients with brain metastases. In this perspective we contend that a large number of patients can be offered the alternative of treatment with this modality alone, reserving whole brain radiation for salvage. The relevant data will be presented supporting this approach, with emphasis on the toxicities of whole brain radiation and equivalence of survival outcomes regardless of treatment approach. Patient selection for radiosurgery alone will also be addressed.