Posterior fossa metastases: risk of leptomeningeal disease when treated with stereotactic radiosurgery compared to surgery.

INTRODUCTION: Leptomeningeal disease (LMD) represents a diffuse form of central nervous system metastatic disease that is often associated with poor quality of life and prognosis. Our objective was to compare the incidence of LMD in patients with posterior fossa metastases (PFM) following stereotactic radiosurgery (SRS) versus surgical resection.
METHODS: The medical records of 93 patients aged 57.9 +/- 10.8 years (mean +/- SD) with PFM treated at the Cleveland Clinic from 1995 to 2001 were analyzed retrospectively. Treatments consisted of surgery with whole brain radiation therapy (WBRT) or SRS with or without WBRT. The impact of age, Karnofsky performance status (KPS) at presentation, Radiation Therapy Oncology Group, recursive partitioning analysis (RPA) class, status of extracranial disease, number, size, volume, pathology of brain metastases and steroid use were studied using univariate and multivariate analyses.
RESULTS: There were 80 evaluable patients (10 lost to follow-up and three excluded for supratentorial surgery with subsequent LMD). LMD occurred after the surgical removal of the PFM in 9 of 18 patients (50%), whereas LMD occurred after SRS in 4 of 62 patients (6.5%) (p = 0.0028). Multivariate analysis also showed that patients who had surgery were more likely to develop LMD compared to patients treated with SRS (p = 0.0024). Patients had a median KPS decline of 30 points after LMD was diagnosed. There was no statistically significant difference in survival of patients with LMD and the rest of the patients (13.5 vs. 11.7 months, p = 0.7659). Patients treated surgically had significantly larger lesions (3.43 +/- 0.74 vs. 1.96 +/- 0.95 cm maximum diameter, p < 0.0001). All surgical patients belonged to RPA class II at diagnosis. Their survival was not different from the RPA class II patients in the SRS group. Surgery and SRS had comparable complication rates (8.1% vs. 5.6%, p = 0.99), although the surgical complications were more serious (e.g. hemorrhage, CSF leak). The duration of steroid use was longer after SRS compared to surgery (2.1 +/- 3.6 vs. 1.3 +/- 2.4 months); however, the difference was not statistically significant. Myopathy and psychosis in one patient after SRS, were the only steroid-related complications. There was no statistically significant association between the primary tumor type and the presence of LMD.
CONCLUSIONS: In this retrospective analysis of patients with PFM, SRS was associated with a lower incidence of LMD than was surgery. Although LMD was associated with rapid and considerable decline in the quality of life, it did not influence the overall survival. SRS was associated with less serious complications than surgery. Surgery in this study was performed on patients with larger lesion sizes and a trend toward poorer initial performance status, which could bias these results. A prospective study directly comparing surgery and SRS and further evaluating the significance of LMD in PFM is warranted.