Radiosurgery for recurrent brain metastases after whole-brain radiotherapy : factors affecting radiation-induced neurological dysfunction

Abstract

Objective: We retrospectively analyzed survival, local control rate, and incidence of radiation toxicities after radiosurgery for recurrent metastatic brain lesions whose initial metastases were treated with whole-brain radiotherapy. Various radiotherapeutical indices were examined to suggest predictors of radiation-related neurological dysfunction.

Methods: In 46 patients, total 100 of recurrent metastases (mean 2.2, ranged 1-10) were treated by CyberKnife radiosurgery at average dose of 23.1 Gy in 1 to 3 fractions. The median prior radiation dose was 32.7 Gy, the median time since radiation was 5.0 months, and the mean tumor volume was 12.4 cm(3). Side effects were expressed in terms of radiation therapy oncology group (RTOG) neurotoxicity criteria.

Results: Mass reduction was observed in 30 patients (65%) on MRI. After the salvage treatment, one-year progression-free survival rate was 57% and median survival was 10 months. Age (<60 years) and tumor volume affected survival rate (p=0.03, each). Acute (</=1 month) toxicity was observed in 22% of patients, subacute and chronic (>6 months) toxicity occurred in 21%, respectively. Less acute toxicity was observed with small tumors (<10 cm(3), p=0.03), and less chronic toxicity occurred at lower cumulative doses (<100 Gy, p=0.004). "Radiation toxicity factor" (cumulative dose times tumor volume of <1,000 Gyxcm(3)) was a significant predictor of both acute and chronic CNS toxicities.

Conclusion: Salvage CyberKnife radiosurgery is effective for recurrent brain metastases in previously irradiated patients, but careful evaluation is advised in patients with large tumors and high cumulative radiation doses to avoid toxicity.

Keywords: Brain; Metastasis; Radiosurgery; Radiotherapy; Recurrence; Toxicity.

Figures

Fig. 1

Local control of treated lesions. The graph illustrates the median local control of treated lesions is 21 months and 1-year progression free survival is 64%.

Fig. 2

Survival of patients. The median survival after CyberKnife treatment for recurrent brain metastases is 10 months and 1-year survival rate is 39%.

Fig. 3

Incidence of radiation-induced central nervous system toxicity according to the time after the treatment.

Fig. 4

Scatter diagram of acute side effects plotted as a function of summated dose versus tumor volume. Filled rectangle represents occurrence of radiation-induced side effect with its grade on the top of it. Dotted line indicates lower limit of tumor volume for the occurrence of acute side effect.

Fig. 5

Scatter diagram of chronic side effects plotted as a function of summated dose versus tumor volume. Filled rectangle represents occurrence of radiation-induced side effect with its grade on the top of it. Dotted line indicates lower limit of summated dose for the occurrence of chronic side effect.