gms | German Medical Science

Objective: The aim of our study is to evaluate GKRS for BMs of gastrointestinal (GI) and genitourinary (GU) tumors. Gamma Knife radiosurgery (GKRS) is a safe and effective treatment option for patients with brain metastases (BM). The most common primary tumors are lung cancer and breast cancer. However, secondary lesions, which are considered as less sensitive to radiation, such as BMs of colorectal cancer or renal cell-carcinoma, do exist albeit much less frequently.

Methods: This is a retrospective single center analysis of 62 patients with 206 BMs undergoing GKRS due BMs of GI (n=28) or GU (n=34). Patients were assessed using the Graded Prognostic Assessment, Recursive partitioning analysis, and Score Index for Radiosurgery. Treatment planning was mainly conducted on the 50% isodose line (range: 45 – 80%) and included the whole tumor volume as seen on T1 contrast-enhanced MRIs. Most patients (60%) underwent single GKRS. However, several patients (40%) were treated more than one time for newly diagnosed BMs or due to a two-fraction dose staged treatment concept. The median margin and central dose were 19 Gy (range: 17 Gy – 20 Gy) and 36 Gy (range: 23 Gy – 44 Gy) for single fraction GKRS which was applied on the majority of BMs (159/ 206, 77%). The median margin and central dose were 14Gy (range: 5 Gy – 17 Gy) and 28 Gy (range: 10 Gy – 36 Gy) for two-fraction GKRS or boost treatment in combination with WBRT.

Results: A majority of patients (89%) was rated as RPA class II; three patients (3%) were classified as RPA class I, and five patients (8%) were classified as RPA class III at time of BM diagnosis. At the time of first GKRS patients presented with a median KPS score of 80. At time of last follow-up the vast majority of patients presented without any post-treatment complications. In 16 patients a six-month-follow-up is not yet available. In the remaining patients 66% presented with stable or decreased lesions at six-month-follow-up after first GKRS1. Unfortunately, several patients had succumbed to their disease (17%) prior to the six-month- follow-up or were lost-to-follow-up (11%). A progression of treated BMs was diagnosed in 4% of patients at six-month-follow-up after GKRS1. However, pooling all radiosurgical treatments, a progression rate was diagnosed in 9% of patients at last follow-up.

Conclusion: GKRS seems to be a reasonably safe and effective treatment option, even for BMs generally considered as radiation resistant. GKRS can be applied as sole treatment or as boost treatment in combination with WBRT depending on target volume and number of BMs.