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

Abstract

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. ¹⁸F-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 ¹⁸F-FDG PET/CT scans for detecting local recurrence in patients beyond 3 mo after nCRT and to determine when radiation-induced esophagitis has resolved. <b>Methods:</b> 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 ¹⁸F-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. <b>Results:</b> 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 (<i>P</i> < 0.001, independent-samples <i>t</i> test). In patients with ongoing cCR, SUL_max was lowest at 11 mo after nCRT. <b>Conclusion:</b> Serial ¹⁸F-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.