Glioblastoma (GBM) is the most common brain cancer among adults and patients and has an overall survival (OS) of 15 months. Nowadays brain tumours are not taken in evaluation in relation to the brain area in which they are located. Recent studies have demonstrated that their prognosis is not independent of the structural organisation of the brain: in particular, white matter fibres disconnection degrees can be considered as a prognosis biomarker. The present invention refers to an algorithm for determining a new prognostic index of a brain tumour and it has been already implemented in a software with a user-friendly graphical interface (GUI). The method provides an indirect estimate of the damage that the tumour causes in patients, through data analysis comparison. The prognostic index, together with OS proves how different tumours in different brain areas can cause a peculiar damage, affecting the patient’s prognosis.