Phase I Trial of Intensity-Modulated Hyperfractionated Radiotherapy Boost with Concurrent Chemotherapy Immediately Following Standard Chemoradiotherapy in Patients Primarily with Advanced Intra-thoracic/Cervical Esophageal Squamous Cell Carcinomas

Purpose Local persistence and relapse of disease in the gross tumor volume (GTV) account for the majority of treatment failures after standard chemoradiation therapy. The primary objective of this phase 1 trial was to define the maximum tolerated dose (MTD) of a hyperfractionated radiation therapy (HFRT) boost to the GTV with concurrent weekly paclitaxel and carboplatin after standard-dose chemoradiation therapy, using image guided intensity modulated radiation therapy techniques. Methods and Materials Eligible patients were given weekly doses of paclitaxel (45 mg/m2) and carboplatin (area under the curve 1.5) for 5 weeks with concurrent radiation therapy (50 Gy), immediately followed by an HFRT boost to the GTV with the same chemotherapy regimen. The boost doses were escalated in increments of 7.2 Gy delivered in 6 twice-daily fractions of 1.2 Gy using a modified Fibonacci design. Once the MTD was established, additional patients were treated at that dose to determine the safety. Results Thirty-one patients fulfilled the inclusion criteria. The incidence of dose-limiting toxicity was 0 of 3, 0 of 3, 0 of 3, 1 of 6 (grade 4 esophagitis), 0 of 3, and 2 of 3 (1 case each of grade 5 esophageal fistula and grade 3 pneumotitis) at 7.2, 14.4, 21.6, 28.8, 36, and 43.2 Gy, respectively, indicating an MTD of 36 Gy. Ten patients treated with this MTD showed no dose-limiting toxicities. The most common acute grade 3 or greater toxicities were esophagitis (26%) and neutropenia (19%). Late toxicity of grade 2 esophageal stricture occurred in 4 patients. The overall response rate was 84% (95% confidence interval, 42%-93%) in the entire cohort. The 1-year local control rate was 100% among those receiving a cumulative dose of the MTD or greater. Conclusions The MTD of the HFRT boost after standard chemoradiation therapy in the setting of concurrent chemotherapy was 36 Gy, resulting in the cumulative tumor dose of 86 Gy in patients primarily with advanced intrathoracic/cervical esophageal squamous cell carcinomas and not adenocarcinomas of the gastroesophageal junction. A phase 2 study to further evaluate this regimen is underway.