Objective: To better define the management of unique intradural extramedullary spinal metastases (IESM) from solid cancers of non-neurogenic origin, in particular regarding leptomeningeal metastasis (LM).
Methods: We conducted a retrospective and multicentric case-control study including 11 cases of IESM matched with 11 cases of LM. Primary endpoint was overall survival; secondary endpoints were diagnostic criteria and prognostic factors.
Results: Descriptive analysis showed a clinically significant difference between IESM and LM patients regarding pre-existing neurological deficit (45.5% vs. 90.1%, p=0.06) and malignant cells in cerebrospinal fluid (0% vs. 54.5%, p=0.03). The median overall survival was significantly higher for IESM patients (732 days) than for patients with LM (53 days; p<0.0002). Multivariate analysis showed that pre-existing neurological deficit was a negative prognostic factor for overall survival (HR, 10.2; 95%CI, 1.88-102; p=0.04), on the contrary to functional improvement upon treatment (HR, 0.01; 95%CI, 0.00-0.52; p=0.04). We propose the following diagnostic criteria for IESM: a) a solid lesion located within the intradural extramedullary space, b) the absence of other leptomeningeal lesion seen on full-spine injected magnetic resonance imaging, c) the absence of malignant cells in cerebrospinal fluid, and d) a histological confirmation of the metastatic nature of the lesion.
Conclusion: The significant difference in survival between IESM and LM suggests that they are two distinct evolutions of the metastatic disease. Distinguishing IESM also bears therapeutic consequences, as patients can benefit from a focal surgical treatment with functional improvement and extended survival.
From: Intradural Extramedullary Spinal Metastases of Non-neurogenic Origin: A Distinct Clinical Entity or a Subtype of Leptomeningeal Metastasis? A Case-Control Study by Knafo et al.