Conventional MRI does not reliably distinguish radiation necrosis from tumor recurrence after stereotactic radiosurgery

• Published in: Journal of neuro-oncology 2012-08, Vol.109 (1), p.149-158
• Main Authors: Stockham, Abigail L., Tievsky, Andrew L., Koyfman, Shlomo A., Reddy, Chandana A., Suh, John H., Vogelbaum, Michael A., Barnett, Gene H., Chao, Samuel T.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Brain; Brain Neoplasms - secondary; Brain Neoplasms - surgery; Clinical Study; Contrast Media; Diagnosis, Differential; Disease Progression; Female; Follow-Up Studies; Humans; Magnetic Resonance Imaging; Male; Medicine; Medicine & Public Health; Metastases; Middle Aged; Necrosis; Neoplasm Recurrence, Local - diagnosis; Neoplasm Recurrence, Local - surgery; Neoplasm Staging; Neoplasms - pathology; Neoplasms - surgery; Neuroimaging; Neurology; Oncology; Prognosis; Radiation; Radiation Injuries - diagnosis; Radiation Injuries - etiology; Radiosurgery - adverse effects; Regression analysis; Sensitivity and Specificity; Substance P; Survival Rate; Tumors
• ISSN: 0167-594X; 1573-7373
• DOI: 10.1007/s11060-012-0881-9

Distinguishing radiation necrosis (RN) from tumor recurrence after stereotactic radiosurgery (SRS) for brain metastases is challenging. This study assesses the sensitivity (SN) and specificity (SP) of an MRI-based parameter, the “lesion quotient” (LQ), in characterizing tumor progression from RN. Records of patients treated with SRS for brain metastases between 01/01/1999 and 12/31/2009 and with histopathologic analysis of a subsequent contrast enhancing enlarging lesion at the treated site at a single institution were examined. The LQ, the ratio of maximal nodular cross sectional area on T2-weighted imaging to the corresponding maximal cross sectional area of T1-contrast enhancement, was calculated by a neuroradiologist blinded to the histopathological outcome. Cutoffs of 0.6 have been previously suggested to have correlated with RN, mixed findings and tumor recurrence, respectively. These cutoff values were evaluated for SN, SP, positive predictive value (PPV) and negative predictive value (NPV). Logistic regression analysis evaluated for associated clinical factors. For the 51 patients evaluated, the SN, SP, PPV and NPV for identifying RN (LQ  0.6) were 59, 41, 62 and 39 %, respectively. Standard MRI techniques do not reliably discriminate between tumor progression and RN after treatment with SRS for brain metastases. Additional imaging modalities are warranted to aid in distinguishing between these diagnoses.