Cumulative Intracranial Tumor Volume as a Prognostic Factor in Patients with Brain Metastases Undergoing Stereotactic Radiosurgery

Approximately 25–35% of all cancer patients suffer from brain metastases (BM), and many of them—in particular, those with a limited number of intracranial tumors—are treated with stereotactic radiosurgery (SRS). Accurate prediction of survival remains a key clinical challenge in this population. Several prognostic scales have been developed to facilitate this prognostication, including the Recursive Partitioning Analysis (RPA) classification, the modified Recursive Partitioning Analysis (mRPA) subclassifications, the Basic Score for Brain Metastases (BS-BM), the Score Index for Radiosurgery (SIR), the Graded Prognostic Assessment (GPA), and the diagnosis-specific Graded Prognostic Assessment (dsGPA). However, none of these scales include consideration of the cumulative intracranial tumor volume (CITV), which is defined as the sum of all intracranial tumor volumes. Since there is mounting evidence that the CITV carries significant prognostic value in SRS-treated patients with BM, this variable should be considered during survival prognostication, along with other pertinent clinical, pathological, and molecular characteristics.