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Overall survival of patients after stereotactic cryodestruction was analyzed according to the Kaplan–Meier method from the time of surgery. The median actuarial survival in cases of AA and GBM was 46.9 and 12.4 months, respectively. In cases of DA the median survival was not reached, whereas 5-year survival rate was 92.9%.

Fig. 2. A 22-year-old patient with diffuse astrocytoma of the right thalamus. The tumor had hyperintense signal on T2-weighted MRI (a) and inhomogeneous uptake of ¹¹C-methionine on PET (b), which were used for planning of stereotactic biopsies and cryodestruction (ovals); 24 h after the procedure, necrotic areas with diameter of 5–6 mm surrounded by perilesional edema were noted within the targets on T2-weighted images (c), DWI (d), and ADC map (e). Four months later, these areas evolved into small cysts with distinct margins (f).

As recommended by the Guidelines for Neuro-Oncology: Standards for Investigational Studies (GNOSIS [39]), survival of patients treated with stereotactic cryodestruction was compared with the outcome in two historical cohorts. The first one included 49 patients (32 men and 17 women; age range 16–67 years) with DA (11 cases), AA (29 cases) and GBM (9 cases), who underwent stereotactic tumor biopsy followed by adjuvant FRT and chemotherapy in our clinic. Since comparison of the results of therapeutic trials with previous peer-reviewed reports may better characterize treatment effects [40, 41], the second control cohort included 242 DA, 93 AA and 448 GBM presented in 14 PubMed-cited articles, which were published between 1989 and 2005 and highlighted survival of adults with supratentorial gliomas after stereotactic biopsy [7, 24, 42–53]. Comparison with both historical control and literature data showed possible survival advantages in patients treated with stereotactic cryodestruction (Table 2).

Fig. 3. A 66-year-old patient with diffuse astrocytoma of the right insula. The tumor had mostly hyperintense signal and indistinct borders on T2-weighted images (a). On the second day after stereotactic cryodestruction an ablation area within the neoplasm was characterized by heterogeneous signal intensity and was accompanied by perilesional edema and mild effacement of the cerebral sulci (b). At 14 (c) and 82 (d) months after surgery, formation of a cyst with distinct margins became evident as well as moderate expansion of the cerebral ventricles.

Table 2. Comparative survival of patients after stereotactic biopsy and cryodestruction of supratentorial gliomas

Multivariate analysis with a Cox proportional hazards regression model was done in our cohort of patients with DA to evaluate the prognostic significance of stereotactic cryodestruction, its volume, patient age, KPS score, pre- and postoperative tumor volumes. Postoperative survival was significantly associated with stereotactic cryodestruction of the tumor (p < 0.05) and KPS score (p = 0.0005). It can be suggested that this survival advantage may have resulted from selective alteration of the metabolically active areas within the LGG.