Sequential boost of intensity‐modulated radiotherapy with chemotherapy for inoperable esophageal squamous cell carcinoma: A prospective phase II study

PURPOSE: This prospective phase II study aimed to determine the efficacy and tolerability of sequential boost of intensity‐modulated radiation therapy (IMRT) with chemotherapy for patients with inoperable esophageal squamous cell carcinoma (ESCC). METHODS: Patients with histologically or cytologically proven inoperable ESCC were enrolled in this study (ChiCTR‐OIC‐17010485). A larger target volume for subclinical lesion was irradiated with 50 Gy, and then, a smaller target volume only including gross tumor was boosted to 66 Gy. The fraction dose was 2 Gy, and no elective node was irradiated. Concurrent and consolidation chemotherapy of fluorouracil (600 mg/m(2), days 1‐3) plus cisplatin (25 mg/m(2), days 1‐3) was administered every 4 weeks, for 4 cycles in total. The primary endpoint was 2‐year progression‐free survival (PFS). RESULTS: Eighty‐eight patients were enrolled in this study. The median age was 65 years (range: 45‐75 years), and 69 patients (78.4%) were men. With the median follow‐up of 26 (range: 3‐95) months, the 2‐ and 5‐year PFS were 39.3% and 36.9%, respectively, and overall survival (OS) were 57.1% and 39.2%, respectively. Tumor stage and concurrent chemotherapy were independent OS predictors. Major acute adverse events were myelosuppression and esophagitis, most of which were grades 1‐2. Nine percent and 2.3% of patients had grade 3 acute esophagitis and late esophageal strictures, respectively. CONCLUSIONS: Sequential boost to 66 Gy by IMRT with chemotherapy was safe and effective for inoperable ESCC. A randomized phase III study to compare with standard dose of 50 Gy is warranted.