Local Control and Toxicity of a Simultaneous Integrated Boost for Dose Escalation in Locally Advanced Esophageal Cancer: Interim Results from a Prospective Phase I/II Trial

Introduction Approximately 50% of recurrences after standard-dose chemoradiation for locally advanced esophageal cancer occur within the gross tumor volume (GTV). In this prospective phase I/II clinical trial, we explored the use of a simultaneous integrated boost (SIB) dose to the GTV. Methods Forty-four patients with unresectable esophageal cancer received chemoradiation with an SIB of 58.8 to 63 Gy to the GTV and 50.4 Gy to the planning target volume, all in 28 fractions, with 5 weeks of concurrent docetaxel and fluorouracil or capecitabine. The end points were maximum tolerated dose, time to local failure, and clinical response. Results Excluding those with less than 6 months of follow-up, 38 patients were evaluated at the time of analysis. The median age was 65 years (range 37–84). Most patients (71%) were men; 84% had T3 disease, 37% had N1 disease, 26% had N2 disease, 13% had M1 disease, and 50% had adenocarcinoma. The maximum tolerated SIB dose was 63 Gy. None experienced Common Terminology Criteria for Adverse Events grade 4 or 5 toxicity. At a median follow-up time of 13.3 months (range 1.2–36.2), 11 (29%) had local failure (median time to local failure 2.5 months [range 1.5–23.9]). A comparison with 97 similar patients who received 50.4 Gy without an SIB showed that the SIB reduced the local failure rate for patients with node-positive disease (13% versus 56%, p = 0.04), adenocarcinoma (26% versus 59%, p = 0.02), or stage III–IV disease (29% versus 55%, p = 0.04). Conclusions SIB intensity-modulated radiation therapy to gross primary disease may improve local control for patients with unresectable locally advanced esophageal cancer, especially those with adenocarcinoma.