title: Pulmonary imaging after stereotactic radiotherapy-does RECIST still apply?
abstract: The use of stereotactic ablative radiotherapy (SABR) for the treatment of primary lung cancer and metastatic disease is rapidly increasing. However, the presence of benign fibrotic changes on CT imaging makes response assessment following SABR a challenge, as these changes develop with an appearance similar to tumour recurrence. Misclassification of benign fibrosis as local recurrence has resulted in unnecessary interventions, including biopsy and surgical resection. Response evaluation criteria in solid tumours (RECIST) are widely used as a universal set of guidelines to assess tumour response following treatment. However, in the context of non-spherical and irregular post-SABR fibrotic changes, the RECIST criteria can have several limitations. Positron emission tomography can also play a role in response assessment following SABR; however, false-positive results in regions of inflammatory lung post-SABR can be a major clinical issue and optimal standardized uptake values to distinguish fibrosis and recurrence have not been determined. Although validated CT high-risk features show a high sensitivity and specificity for predicting recurrence, most recurrences are not detected until more than 1-year post-treatment. Advanced quantitative radiomic analysis on CT imaging has demonstrated promise in distinguishing benign fibrotic changes from local recurrence at earlier time points, and more accurately, than physician assessment. Overall, the use of RECIST alone may prove inferior to novel metrics of assessing response.
authors.affiliation: 1 Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Mattonen
authors.affiliation: 1 Department of Medical Biophysics, The University of Western Ontario, London, ON, Canada.|2 Department of Oncology, The University of Western Ontario, London, ON, Canada.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Ward
authors.affiliation: 2 Department of Oncology, The University of Western Ontario, London, ON, Canada.|3 Division of Radiation Oncology, London Health Sciences Centre, London, ON, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Palma
mesh_terms: D055011:Ablation Techniques; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D009364:Neoplasm Recurrence, Local / Q000209:etiology; D015588:Observer Variation; D000072103:Oncologists / Q000592:standards; D055420:Perfusion Imaging / Q000379:methods; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods; D000072177:Radiologists / Q000592:standards; D019275:Radiopharmaceuticals; D016634:Radiosurgery / Q000379:methods*; D066066:Response Evaluation Criteria in Solid Tumors; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18