Factors predicting progression of low-grade diffusely infiltrating astrocytoma

Low-grade diffuse astrocytoma (DA) is considered benign tumor (World Health Organization [WHO] grade II), but it has an inherent tendency for malignant progression, which is quite variable.

To identify malignant progression in an individual case of DA, we studied the clinico-radiological and immunohistochemical factors and correlated with progression of DA at a dedicated tertiary level neurosciences centre NIMHANS, Bangalore, India.

Consecutive adult patients who had undergone tumor decompression for lobar supratentorial DA at our institute from 1994 to 1998 were retrospectively selected and followed up for clinico-radiological progression. The clinico-radiological and histomorphological features were studied. With the use of immunohistochemistry, proliferation index [MIB-1 labeling index (LI)], p53 protein expression, microvessel density (MVD) count [assessed using anti-CD34 antibody] were analyzed and correlated with progression-free survival (PFS) Results: There were 13 patients. Mean age was 34 years. The most common presenting symptom was seizures. The median follow-up was 54 months. There were four recurrences, with median interval of 75 months. Eight patients received radiotherapy. Younger patients (<40 years), seizure as the presenting symptom and postoperative radiotherapy were associated with longer PFS, while gemistocytic morphology (>20% gemistocytic cells), MVD value >20 correlated with shorter PFS, albeit statistically insignificant. MIB1 LI did not correlate with recurrence pattern. Moreover, p53 LI > 10% correlated with early progression (P = 0.04).

Our study highlights some of the clinical, histological and immunohistochemical parameters that predict progression on DA. Validation on a larger sample may be useful to plan appropriate treatment in an individual case.