Development and adaptations of the Graded Prognostic Assessment (GPA) scale: a systematic review

The Graded Prognostic Assessment (GPA) score has the best accuracy among prognostic scales for patients with brain metastases (BM). A wide range of GPA-derived scales have been established to different types of primary tumor BM. However, there is a high variability between them, and their characteristics have not been described altogether yet. We aim to summarize the features of the existent GPA-derived scales and to compare their predictor factors and their uses in clinical setting. Medline was searched from inception until January 2023 to identify studies related to the development, update, or validation of GPA. The initial search yielded 1,083 results. 16 original studies and 16 validation studies were included, comprising a total of 33,348 patients. 13 different scales were assessed, including: GPA, Diagnosis-Specific GPA, Extracranial Score, Lung-molGPA, Updated Renal GPA, Updated Gastrointestinal GPA, Modified Breast GPA, Integrated Melanoma GPA, Melanoma Mol GPA, Sarcoma GPA, Hepatocellular Carcinoma GPA, Colorectal Cancer GPA, and Uterine Cancer GPA. The most prevalent prognostic predictors were age, Karnofsky Performance Status, number of BM, and presence or absence of extracranial metastases. Treatment modalities consisted of whole brain radiation therapy, stereotactic radiosurgery, surgery, cranial radiotherapy, gamma knife radiosurgery, and BRAF inhibitor therapy. Median survival rates with no treatment and with a specific treatment ranged from 6.1 weeks to 33 months and from 3.1 to 21 months, respectively. Original GPA and GPA-derived scales are valid prognostic tools, but with heterogeneous survival results when compared to each other. More studies are needed to improve scientific evidence of these scales.