Efficacy Of 20 Gy Gamma Knife Radiosurgery For Brain Metastases = 2 Cm In Size

Keywords: gamma knife, outcome, brain metastasis, cancer, radiosurgery

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     To analyze the rate of local control (LC) of 20 Gy gamma knife radiosurgery (GKR) in patients with 1 to 3 brain metastases ? 2 cm in greatest diameter.
     A retrospective analysis of 114 consecutive adults with KPS.  60 who received GKR for 1 to 3 brain metastases. 2 cm in size was performed. Five patients lacked detailed follow-up and were excluded from analysis, leaving 109 for outcome analysis. The study group consisted of 34 males and 75 females with a median age of 61.2 years at time of GKR.
     All patients received 20 Gy to the 50%-isodose line. Following treatment, patients underwent MRI at 6 weeks and every 3 months thereafter. All patients had at least 6 months follow-up following GKR unless death ensued prior to that time.
     One hundred-nine patients underwent 20 Gy GKR treatment of 164 metastases at initial presentation and 33 patients received salvage 20 Gy GKR to 95 new lesions. Median tumor volume was 0.19 cc (mean: 0.46±0.68; range: 0.002—4.5 cc). Four patients with 4 metastases died before post-treatment imaging at 6 weeks and were excluded from LC analysis, yielding a total of 255 metastases with complete follow-up. Twenty-six patients (23.9%) are alive at a median last follow-up time of 29.9 months from initial GKR. Median overall survival for the entire group was 13.8 months from GKR. Local failure occurred in 17 of 255 treated lesions (6.7%), yielding an overall crude rate of LC of 93.3%. Actuarial local control at 6-, 12-, 24- and 36-month was 96%, 93%, 89% and 88%, respectively. Radiation necrosis occurred in 3 patients (2.8%) and 3 patients (2.8%) were left with permanent neurological deficits.
     This is a retrospective study.
     Among patients with brain metastases, 2 cm who have not received WBRT, GKR with 20 Gy provides a high rate of local control as initial or salvage treatment with low morbidity.
      GKR appears to be durable given sustained high rate of LC at 2 and 3 years following treatment. Close follow-up seems helpful to identify new metastases early, while small in size, which would be amenable to salvage GKR with 20 Gy.


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