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 , days 1-3) plus cisplatin (25 mg/m , 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.