Fig 5.

A 58-year-old man with EGFR-mutant NSCLC treated with erlotinib. Pretreatment images (A and C) show a solidly enhancing left frontal brain metastasis measuring 17 mm in diameter. Posttreatment images (B and D) demonstrate the implications of different measurement methods on the response to therapy. The measurement on B includes both the cystic and solid components of the lesion and demonstrates an increase of 25% of the lesion size, consistent with progressive disease. The measurement on D was performed according to the RANO criteria specifications, which only include the enhancing nodular component of the lesion, which has a perpendicular diameter of at least 5 mm. This method of measurement calculated a decrease of 31%, which is consistent with partial response to therapy. This patient continued to have a response to therapy and further decrease in the size of this lesion.