Diagnostic Utility of MR Spectroscopy in Differentiating Recurrent Brain Tumors from Radiation Necrosis: A Prospective Single-Center Study

Abstract

 Introduction: Magnetic Resonance Spectroscopy (MRS) is a non-invasive imaging technique that provides valuable metabolic insights, supplementing conventional MRI. Differentiating between recurrent brain tumors and radiation necrosis is challenging, as both may appear similar radiologically. Accurate identification is essential for guiding appropriate treatment, avoiding unnecessary interventions, and improving patient outcomes by distinguishing viable tumor tissue from post-therapeutic necrotic changes. Aim and Objective: To evaluate the diagnostic utility of MRS in distinguishing recurrent brain tumors from radiation necrosis in post-treatment patients, specifically using Cho/NAA, Cho/Cr and NAA/Cr metabolite ratios, and to assess its potential in reducing invasive procedures. Materials and Methods: A prospective single-center study was conducted between November 2023 and January 2025 at Tamil Nadu Government Multi Super Specialty Hospital, Chennai. Thirty four patients aged 10–70 years with previously treated primary brain tumors and new or worsening contrast-enhancing MRI lesions were included. Multivoxel MRS was performed using a 1.5T scanner. Patients with chronic renal failure, extreme ages, or incomplete follow-up were excluded. ROC curve analysis of metabolite ratios was performed using MedCalc version 23.2.1.Results: Cho/NAA ratio showed the highest diagnostic performance with an AUC of 0.965, sensitivity of 93%, and specificity of 100%, achieving 96.5% overall accuracy. The Cho/Cr ratio had an AUC of 0.820 and good diagnostic value, while NAA/Cr showed lower sensitivity but high specificity, supporting its limited standalone utility. Conclusion: MRS is a highly accurate tool in differentiating recurrent brain tumors from radiation necrosis, with Cho/NAA emerging as the most reliable marker. Routine incorporation of MRS into post-treatment imaging protocols can improve diagnostic accuracy, reduce invasive procedures, and guide clinical decision-making.