Surveillance of Clinically Complete Responders Using Serial 18 F-FDG PET/CT Scans in Patients with Esophageal Cancer After Neoadjuvant Chemoradiotherapy.

Active surveillance for patients with esophageal cancer and a clinically complete response (cCR) after neoadjuvant chemoradiotherapy (nCRT) is being studied. Active surveillance requires accurate clinical response evaluations. ¹⁸ F-FDG PET/CT might be able to detect local tumor recurrence after nCRT as soon as the esophagus recovers from radiation-induced esophagitis. The aims of this study were to assess the value of serial ¹⁸ F-FDG PET/CT scans for detecting local recurrence in patients beyond 3 mo after nCRT and to determine when radiation-induced esophagitis has resolved. Methods: This retrospective multicenter study included patients who had cCR after nCRT, who initially declined surgery, and who subsequently underwent active surveillance. Clinical response evaluations included ¹⁸ F-FDG PET/CT, endoscopic biopsies, and endoscopic ultrasound with fine-needle aspiration at regular intervals. SUV _max normalized for lean body mass (SUL _max ) was measured at the primary tumor site. The percentage change in SUL _max (Δ%SUL _max ) between the last follow-up scan and the scan at 3 mo after nCRT was calculated. Tumor recurrence was defined as biopsy-proven vital tumor at the initial tumor site. Results: Of 41 eligible patients, 24 patients had recurrent disease at a median of 6.5 mo after nCRT and 17 patients remained cancer free during a median follow-up of 24 mo after nCRT. Five of 24 patients with tumor recurrence had sudden intense SUL _max increases of greater than 180%. In 19 of 24 patients with tumor recurrence, SUL _max gradually increased (median Δ%SUL _max , +18%), whereas SUL _max decreased (median Δ%SUL _max , -12%) in patients with ongoing cCR ( P < 0.001, independent-samples t test). In patients with ongoing cCR, SUL _max was lowest at 11 mo after nCRT. Conclusion: Serial ¹⁸ F-FDG PET/CT might be a useful tool for detecting tumor recurrence during active surveillance. In patients with ongoing cCR, the lowest SUL _max was reached at 11 mo after nCRT, suggesting that radiation-induced esophagitis had mostly resolved by that time. These findings warrant further evaluation in a larger cohort.
(© 2021 by the Society of Nuclear Medicine and Molecular Imaging.)