Background: To investigate the safety and tolerability of simultaneous integrated boost (SIB) technique concurrent with elective nodal irradiation (ENI) and dual-drug chemotherapy for patients with unresectable esophageal cancer.
Methods: In phase I, the prophylactic PTV received a stable dose of 50.40Gy/1.80Gy/28f while the boost area was planned with 3 consecutive dose levels: the first dose level was 60.76Gy/2.17Gy/28f, and then escalated approximately every 2 Gy. ENI was incorporated in Clinical Target Volume (CTV), and paclitaxel and nedaplatin were given concurrently for at least 5 weeks. In phase II, enrolled patients were treated with Maximum Tolerated Dose (MTD) obtained in phase I and the compliance rate, survival results and toxicities were evaluated.
Results: From December 2014 to April 2017, 53 patients were enrolled. In phase I, 2 out of 6 patients developed Dose-Limiting Toxicity (DLT) at dose level 1. Due to excessive treatment-related toxicities, the escalation process was suspended and de-escalated to 59.92Gy /2.14Gy /28 f. Three patients were treated at this dose level, all of whom completed at least 5 weeks of chemotherapy and none of whom reached a DLT, determining the newly added dose level to be the MTD. In phase II, 44 patients were treated with MTD, 31 of them (70.0%) completed at least 5 weeks of chemotherapy. The most common Grade 3 or 4 toxicities in phase II included leukopenia (21%) and esophagitis (15%). With a median follow-up time of 16.9 months, 1-y OS, DFS and local failure-free survival were 76.9, 63.6 and 78.8% respectively.
Conclusion: The SIB technique was feasible and safe at the MTD (95% PGTV/PTV 59.92/50.40Gy/28f) concurrent with ENI and dual-drug chemotherapy for patients with unresectable esophageal cancer.
Trial registration: clinicaltrials.gov NCT02429622 . Retrospectively registered on April 24, 2015.
Keywords: Concurrent Chemoradiotherapy; Dose-escalation; Elective nodal irradiation; Esophageal squamous cell carcinoma; Simultaneous integrated boost.