O112 SURVEILLANCE USING FDG-UPTAKE IN THE PRIMARY TUMOUR ON PET/CT IN PATIENTS WITH OESOPHAGEAL CANCER AND A CLINICALLY COMPLETE RESPONSE AFTER NEOADJUVANT CHEMORADIOTHERAPY. (23rd November 2019) - Valkema, M J
Abstract: Aim: In oesophageal cancer patients, clinical response to neoadjuvant chemoradiotherapy (nCRT) according to CROSS is assessed after 12 weeks, potentially followed by active surveillance in case of clinically complete response (cCR). Detection of residual tumour by FDG-PET/CT alone is inaccurate, since this cannot be distinguished reliably from post-radiation oesophagitis. We hypothesize that when inflammation diminishes, increasing FDG-uptake over time may be a sensitive parameter to detect local recurrence. We studied the detection of tumour recurrence with PET/CT during systematic follow-up in clinically complete responders beyond 12 weeks after nCRT. Background & Methods: Patients from the preSANO- and SANO- trials were included who obtained cCR (no residual tumour on bite-on-bite biopsies and EUS with FNA of suspected lymph nodes) 12 weeks after completion of nCRT, but declined subsequent surgery. Patients were offered active surveillance, including PET/CT every 3 months. Standardised uptake values corrected for lean body mass (SUL) were measured at the primary tumour site. The percentage change in maximum SUL value (SULmax) between the last follow-up scan and the scan 12 weeks after nCRT was calculated. Tumour recurrence was defined as biopsy-proven vital tumour. Results: Some 33 patients were eligible for analysis. In 17 of 33 (52%) patients, no biopsy-proven local recurrence was found during a median follow-up of 16 months (range 4.0-25) after CROSS. Some 16 of 33 (48%) patients had tumour recurrence within a median of 6.9 months after CROSS (range 5.3-36). We observed two different patterns of FDG uptake suggesting local recurrence. Three of 16 patients had sudden intense increase in SULmax (mean delta%-SULmax of 216%±42%). In the other 13 of 16 patients with local recurrence, an insidious gradual increase in FDG uptake was seen compared to patients without recurrence: mean delta%-SULmax of 21%±18% versus -10%±22% respectively. Conclusion: Increasing FDG-uptake during active surveillance beyond 12 weeks after nCRT was associated with local recurrence and stable FDG-uptake with ongoing local tumour control. Thus, serial PET/CT might be a useful tool to distinguish tumour recurrence from SUL fluctuations in complete responders. To define a cut-off value of delta%-SULmax for local recurrence a larger number of patients is needed.