Detection of Recurrence After Thoracic Stereotactic Ablative Radiotherapy Using FDG-PET-CT

• Published in: Clinical lung cancer 2022-05, Vol.23 (3), p.282-289
• Main Authors: Sodji, Quaovi H., Harris, Jeremy P., Quon, Andrew, Modlin, Leslie A., Lau, Brianna, Jiang, Alice, Trakul, Nicholas, Maxim, Peter G., Diehn, Maximilian, Loo, Billy W., Hiniker, Susan M.
• Format: Article
• Language: English
• Subjects: 18F-fluorodeoxyglucose-positron emission tomography; Carcinoma, Non-Small-Cell Lung - diagnostic imaging; Carcinoma, Non-Small-Cell Lung - radiotherapy; Fluorodeoxyglucose F18; Humans; Local recurrence; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - radiotherapy; Non–small cell lung cancer; Positive predictive value; Positron Emission Tomography Computed Tomography; Radiopharmaceuticals; Retrospective Studies; Stereotactic Ablative Radiotherapy
• ISSN: 1525-7304; 1938-0690
• DOI: 10.1016/j.cllc.2022.01.006

Differentiating local recurrence (LR) from post-treatment changes following stereotactic ablative radiotherapy (SABR) for thoracic tumors is challenging. We sought to evaluate the performance of FDG-PET-CT in distinguishing recurrence from post-radiation changes in patients with stage I-II non–small cell lung cancer (NSCLC) treated with SABR. We performed a retrospective review of patients with stage I-II NSCLC treated with SABR and subsequently followed with surveillance FDG-PET-CT scans from 2004 to 2014. The radiology reports were coded as 0 or 1 if minimally or substantially concerning for LR, respectively, and correlated with outcome. Prognostic factors for false-positive FDG-PET-CT were assessed using logistic regression models. We identified 145 patients meeting inclusion criteria for the retrospective analysis. Amongst the 39 (26.9%) patients with FDG-PET-CT scans concerning for LR 3 to 24 months after treatment, 14 were confirmed to have LR. Thus, the positive predictive value (PPV) of FDG-PET-CT in identifying LR was 36% (14/39). Factors associated with a false-positive scan included concerning FDG-PET-CT at the earliest post-treatment time point (3 months) (odds ratio 0.67, P= .04) and older age (odds ratio 2.3, P= .02). Our analysis indicates that the PPV of a concerning FDG-PET-CT after SABR for early-stage NSCLC is relatively low, especially at early post-treatment timepoints, but accuracy is improving over time with institutional experience. To evaluate the performance of FDG-PET-CT in distinguishing between local recurrence vs. post radiation changes in patients with early-stage non-small cell lung cancer treated with stereotactic ablative radiotherapy, we performed a retrospective analysis of patients with concerning post-treatment FDG-PET-CT scans. Under these circumstances, the positive predictive value of a concerning FDG-PET-CT is relatively low especially at 3 months.