252. ACCURACY OF PREDICTING RESIDUAL DISEASE AND DISEASE PROGRESSION DURING ACTIVE SURVEILLANCE FOR ESOPHAGEAL CANCER

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Abstract Background In patients with esophageal cancer and a clinical complete response (CCR) after neoadjuvant chemoradiotherapy (nCRT) active surveillance is non-inferior to standard surgery. However, two-thirds of patients have residual disease detected 12 weeks after nCRT and proceed to surgery. In addition, of the patients with CCR 12 weeks after nCRT, nearly half will develop locoregional regrowth at a later time point. We aim to identify predictive factors for achieving (persistent) CCR to improve selection of patients for active surveillance. Methods Data from the SANO-trial were analyzed, including patients who underwent nCRT for esophageal cancer. Logistic regression assessed predictors of CCR at 12 weeks, with potential factors including age, sex, WHO performance status, clinical T- and N-category, histology, differentiation grade, tumor location, and length. For patients with CCR in active surveillance, cause-specific proportional hazards regression identified predictors of sustained CCR (no locoregional regrowth, dissemination, or death) during a minimum two-year follow-up. Discrimination was quantified using the c-statistic with bootstrap validation. Results Of 750 patients, 274 (37%) achieved CCR at 12 weeks. Higher cN-category was associated with lower CCR likelihood (cN2–3 vs. cN0: OR 0.57, 95%CI 0.37–0.88, P < 0.01; c-statistic 0.56). Among 198 patients in active surveillance, 29% sustained CCR after a median follow up of 34 months (IQR:30–40). Higher cN-category (cN2–3 versus cN0: HR 2.08, 95%CI 1.25–3.48, P < 0.01) and adenocarcinoma (squamous cell carcinoma versus adenocarcinoma: HR 0.58, 95%CI 0.34–0.97, P = 0.04) were associated with non-sustained CCR (c-statistic 0.58). Conclusion Standard clinical and tumor parameters are weak predictors of clinical response and the persistence thereof after nCRT. New predictive parameters and better diagnostic tests should be explored to improve patient selection for active surveillance and personalize active surveillance strategies in patients with esophageal cancer.

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