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

Abstract

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 <0.3, 0.3-0.6, and >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 < 0.3) were 8, 91, 25 and 73 %, respectively. For the combination of recurrent tumor and RN (LQ 0.3-0.6) the SN, SP, PPV and NPV were 0, 64, 0 and 83 %. The SN, SP, PPV and NPV of the LQ for recurrent tumor (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.

• Authors: Abigail L Stockham, Andrew L Tievsky, Shlomo A Koyfman, Chandana A Reddy, John H Suh, Michael A Vogelbaum, Gene H Barnett, Samuel T Chao
• Journal: Journal of neuro-oncology (J Neurooncol) Vol. 109 Issue 1 Pg. 149-58 (Aug 2012) ISSN: 1573-7373 [Electronic] United States
• PMID: 22638727 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Contrast Media

Topics

• Adult
• Aged
• Brain Neoplasms (secondary, surgery)
• Contrast Media
• Diagnosis, Differential
• Disease Progression
• Female
• Follow-Up Studies
• Humans
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Necrosis
• Neoplasm Recurrence, Local (diagnosis, surgery)
• Neoplasm Staging
• Neoplasms (pathology, surgery)
• Prognosis
• Radiation Injuries (diagnosis, etiology)
• Radiosurgery (adverse effects)
• Sensitivity and Specificity
• Survival Rate